Sources and References

Primary textbook — Crooks, R., & Baur, K. (2017). Our Sexuality (13th ed.). Cengage Learning.

Supplementary texts — Hyde, J. S., DeLamater, J. D., & Byers, E. S. (2020). Understanding Human Sexuality (13th Canadian ed.). McGraw-Hill Ryerson; Bancroft, J. (2009). Human Sexuality and Its Problems (3rd ed.). Churchill Livingstone; Rathus, S. A., Nevid, J. S., Fichner-Rathus, L., Hamilton, L. D., McKay, A., & Milhausen, D. (2025). Human Sexuality in a World of Diversity (7th Canadian ed.). Pearson Canada.

Online resources — APA PsycNET; Kinsey Institute (kinseyinstitute.org); Society for the Scientific Study of Sexuality (sexscience.org); SIECUS Policy, Research & Education (siecus.org); DSM-5-TR (American Psychiatric Association, 2022).

Chapter 1: A History of Sexual Thought and Scientific Inquiry

The Pre-Scientific Legacy

Human societies have always organized and regulated sexual behaviour through cultural and religious frameworks, yet the systematic scientific study of sexuality is surprisingly recent — barely a century and a half old. Before the emergence of sexology as a discipline, Western understandings of sex were dominated by theological doctrine. In medieval Christian Europe, sexual pleasure was regarded with deep suspicion; procreation within marriage constituted the sole legitimate purpose of sexual activity. Masturbation, oral sex, and nonprocreative intercourse were classified as moral transgressions against natural law, a framework elaborated by scholastic thinkers such as Thomas Aquinas and codified in canon law. This moral architecture did not disappear in the Renaissance or the Enlightenment; rather, it was progressively reinterpreted. Enlightenment natural philosophy began to medicalize what had previously been purely a matter of sin, translating moral categories into pathological ones.

The Victorian era (roughly 1830–1900) represents a pivotal and paradoxical chapter. On the surface, Victorian bourgeois culture cultivated an extreme reticence about sexual matters; the domestic sphere was idealized as one of moral purity, and female sexuality in particular was officially denied. Yet this same period witnessed intense medical and legal preoccupation with sex. Masturbation was reframed as a medical danger causing nervous exhaustion, and a vast hygienic literature warned against its purported consequences — neurasthenia, insanity, even death. These anxieties reflected a broader cultural logic in which sexual energy was understood as a finite resource to be conserved rather than expended, a doctrine that would later be called the “hydraulic model” of libido. Women who did not conform to the asexual ideal were frequently pathologized, and clitoridectomy was advocated in some medical circles as a cure for masturbation and “hysteria.”

The Emergence of Sexology

The late nineteenth century saw the first sustained attempts to describe and classify sexual behaviour empirically, even if the frameworks employed were heavily normative. Richard von Krafft-Ebing’s Psychopathia Sexualis (1886) was among the most influential early texts. Written in the tradition of forensic psychiatry, it catalogued hundreds of cases of what Krafft-Ebing termed “sexual perversions” — sadism, masochism (terms he coined), fetishism, and homosexuality among them. His framework was explicitly degenerationist: deviant sexuality was attributed to hereditary weakness and moral failure. Krafft-Ebing’s work, for all its pathologizing, had the unintended effect of naming and therefore rendering discussible forms of sexual experience that had previously lacked public language.

Havelock Ellis, by contrast, approached sexual diversity from a more sympathetic standpoint. His seven-volume Studies in the Psychology of Sex (1897–1928) argued that many behaviours deemed perversions were natural variations of human sexuality rather than diseases or moral failures. Ellis was among the first to argue that homosexuality was a congenital variation rather than a vice or an illness, a position remarkably progressive for his era. He also wrote extensively on autoeroticism, gender inversion, and sexual symbolism, drawing on case histories and cross-cultural evidence. Ellis’s writing style was humanistic rather than clinical, and his work reached a broad educated readership.

Sigmund Freud occupies a unique and contested position in the history of sexual thought. His Three Essays on the Theory of Sexuality (1905) proposed that sexuality does not originate in puberty but is present from infancy, developing through oral, anal, and phallic stages before reaching adult genitality. Freud’s concept of the libido — a diffuse, undifferentiated sexual drive — and his account of the Oedipus complex, castration anxiety, and penis envy became enormously influential. His claim that repression of sexual impulses was the engine of neurosis made psychoanalysis inseparable from sexuality as a subject. Feminist scholars have extensively criticized Freudian theory for its androcentrism and its pathologizing of female sexuality; the concept of the vaginal orgasm as the “mature” form of female pleasure was disputed by later researchers and is now empirically discredited.

Kinsey and the Survey Tradition

Alfred Kinsey, an entomologist at Indiana University, transformed the study of human sexuality by applying the methods of empirical social science to sexual behaviour. Working with colleagues Wardell Pomeroy and Clyde Martin, Kinsey conducted lengthy, detailed interviews with 5,300 men (published in Sexual Behavior in the Human Male, 1948) and 5,940 women (Sexual Behavior in the Human Female, 1953). His findings were startling to a mid-century American public: masturbation was nearly universal among men; premarital sex and extramarital sex were far more prevalent than public discourse acknowledged; and homosexual experience was far more common than supposed.

Kinsey’s methodology attracted both celebration and criticism. His samples were not random, and incarcerated individuals were overrepresented, raising concerns about generalizability. He also prioritized behaviour over subjective experience. Nevertheless, his fundamental contribution — treating sexuality as a legitimate subject for empirical investigation — opened the door to all subsequent scientific work in the field.

Masters and Johnson: The Laboratory Study of Sexual Response

William Masters and Virginia Johnson pioneered the direct physiological study of human sexual response at Washington University in St. Louis beginning in the 1950s. Using physiological monitoring equipment, they observed over 10,000 sexual response cycles in 382 women and 312 men across more than a decade of research, publishing their findings in Human Sexual Response (1966). Their work was the first to document in precise physiological terms what happens to the human body during sexual arousal and orgasm, and it demolished several persistent myths — most consequentially, Freud’s distinction between clitoral and vaginal orgasms.

Masters and Johnson went on to apply their physiological research to sex therapy, publishing Human Sexual Inadequacy (1970), which introduced the concept of the dual-sex therapy team and techniques such as sensate focus that remain cornerstones of contemporary sex therapy.

Feminist Reconceptualizations and the Sexual Revolution

The social movements of the 1960s and 1970s fundamentally altered both sexual behaviour and the academic study of sexuality. Second-wave feminism challenged the medicalization and control of female sexuality, arguing that medical discourse had systematically served patriarchal interests. Anne Koedt’s “The Myth of the Vaginal Orgasm” (1970) popularized Masters and Johnson’s physiological findings in a feminist context, contending that the cultural privileging of vaginal intercourse reflected male-centred definitions of sex. The legalization of contraception and, in many jurisdictions, abortion shifted power over reproduction to women, enabling a broader reconceptualization of female sexuality as existing for women’s pleasure and not solely for reproduction or male satisfaction.

The HIV/AIDS epidemic, visible in North America by the early 1980s, had profound effects on sexual science and public health. The epidemic initially concentrated among gay men and intravenous drug users, and the inadequate governmental response was widely attributed to homophobia and stigma. Activism by organizations such as ACT UP forced accelerated drug development and changed the relationship between communities and medical research. HIV/AIDS also prompted unprecedented public discourse about sexual practices, condom use, and harm reduction.

The Biopsychosocial Model

Contemporary sexology has largely abandoned single-factor explanations of sexual behaviour in favour of an integrating framework.

Sex-positive frameworks, which emerged from feminist and queer scholarship and activism, challenge pathologizing approaches by emphasizing sexual diversity, consent, and pleasure as positive goods rather than problems to be managed. Intersectional analysis, associated with legal scholar Kimberlé Crenshaw and elaborated by scholars including Patricia Hill Collins, insists that sexuality cannot be understood in isolation from race, class, disability, and other axes of social location, because these dimensions mutually constitute each other in producing embodied sexual experience.

Chapter 2: Gender, Sex, and Sexual Diversity

Conceptual Distinctions

A rigorous understanding of gender and sexuality requires careful attention to a cluster of related but distinct concepts that are often conflated in everyday usage. Biological sex refers to the set of chromosomal, gonadal, hormonal, and anatomical characteristics typically used to classify individuals as male or female, with intersex as an additional category. Gender identity denotes an individual’s deeply felt internal sense of their own gender — as a man, woman, nonbinary person, or other gender — which may or may not correspond to their assigned sex at birth. Gender expression encompasses the ways in which an individual outwardly communicates their gender through dress, behaviour, speech, and other cultural cues. Sexual orientation refers to the pattern of romantic and/or erotic attraction an individual experiences toward others.

Biological Factors in Sex Differentiation

Typical human sex differentiation follows a chromosomal template: individuals with a 46,XX karyotype develop ovaries and a female reproductive system under default developmental pathways, while individuals with a 46,XY karyotype develop testes through the action of the SRY (sex-determining region Y) gene, which initiates testicular differentiation. The testes then produce testosterone and anti-Müllerian hormone (AMH): testosterone drives the development of the Wolffian ducts into the male internal reproductive structures and, via conversion to dihydrotestosterone (DHT), the development of the external genitalia; AMH causes regression of the Müllerian ducts, which would otherwise develop into the uterus, fallopian tubes, and upper vagina. In the absence of SRY signalling, the bipotential gonad defaults to ovarian development.

Hormones produced by the gonads also act on the developing brain during sensitive periods of prenatal development, organizing neural circuits that influence later behaviour — a process referred to as organizational effects, in contrast to the activational effects of hormones during adulthood. Prenatal androgen exposure permanently organizes certain neural structures, while adult hormones activate behaviour through structures already organized.

Gender Roles and Socialization

Gender roles are the behaviours, attitudes, and traits that a given culture associates with being a man or a woman. They are transmitted through a pervasive socialization process beginning in infancy and mediated by parents, peers, media, educational institutions, and religious communities. Social learning theory (Bandura) emphasizes the role of observation, imitation, and reinforcement in acquiring gender-typed behaviour, while cognitive developmental theory (Kohlberg) stresses the child’s active construction of gender constancy as a schema for organizing experience. Gender schema theory (Bem) proposes that children learn culturally appropriate schemas for gender and then apply them to themselves and others, filtering experience through a gender lens.

Cross-cultural variation in gender roles — documented by anthropologists including Margaret Mead — demonstrates that many behaviours considered natural or inevitable in one society are absent or organized differently in others. Gender role strain occurs when individuals cannot or do not conform to dominant cultural expectations, producing psychological distress. Research consistently documents that traditional masculine norms — emphasizing stoicism, dominance, and the suppression of emotional expression — are associated with poorer mental and physical health outcomes for men, including reduced likelihood of seeking medical help.

Transgender and Nonbinary Identities

Transgender is an umbrella term for individuals whose gender identity differs from the sex they were assigned at birth. Nonbinary individuals identify with a gender that is neither exclusively male nor female; this category encompasses genderqueer, genderfluid, agender, and other identities. Gender dysphoria refers to the clinically significant distress that some (but not all) transgender individuals experience as a result of the incongruence between their gender identity and assigned sex.

The Spectrum of Sexual Orientation

Sexual orientation is conventionally described in terms of the sex(es) toward which a person experiences erotic and/or romantic attraction. Heterosexual, homosexual, and bisexual are the most widely recognized categories, but empirical research documents substantial variation in the degree, nature, and consistency of attraction across time. The Klein Sexual Orientation Grid (Klein, 1993) extended Kinsey’s unidimensional scale by rating attraction, behaviour, fantasy, emotional preference, social preference, self-identification, and lifestyle orientation independently and at three time points (past, present, ideal).

Research on the determinants of sexual orientation has implicated genetic factors (twin studies suggest moderate heritability of approximately 40–50%), prenatal hormonal exposure, and birth order effects (the fraternal birth order effect in gay men, attributed to maternal immune responses to H-Y antigen). No single biological variable explains more than a fraction of the variance. No credible evidence supports the efficacy of “conversion” or “reparative” therapies; major professional organizations including the APA, CPA, and CAMH have condemned such practices as ineffective and harmful.

Chapter 3: Sexual Anatomy and Physiology

Female External Anatomy

The external female genitalia are collectively referred to as the vulva and comprise several structures. The mons pubis is the fatty tissue overlying the pubic bone, which becomes covered with hair at puberty. The labia majora are two longitudinal folds of skin and fatty tissue that enclose and protect the more delicate underlying structures; they are homologous to the male scrotum. Medial to the labia majora lie the labia minora, thinner folds of skin without fat tissue, highly variable in size and shape, rich in blood vessels and nerve endings. At the anterior junction of the labia minora is the clitoris, the primary organ of female sexual pleasure.

The vestibule is the space between the labia minora and contains the openings of the urethra, the vagina, and the ducts of the Bartholin’s glands. The Bartholin’s glands (greater vestibular glands) secrete a small amount of fluid at sexual arousal, though their contribution to vaginal lubrication is minimal — the primary source of lubrication is transudation through the vaginal walls. The urethral opening lies anterior to the vaginal opening; the vaginal opening (introitus) may be partially covered by the hymen, a thin fold of mucous membrane that varies widely in form and is not a reliable indicator of previous sexual activity.

Female Internal Anatomy

The vagina is a fibromuscular tube approximately 7–10 cm in length, capable of considerable expansion during intercourse and childbirth. Its walls contain rugae (ridges) that allow distension, and it is self-cleansing through cervical secretions. The cervix is the inferior portion of the uterus protruding into the vaginal vault; the cervical os is the opening through which sperm must pass to reach the uterine cavity. The uterus is a muscular organ roughly the size and shape of an inverted pear; its inner lining, the endometrium, undergoes cyclical changes during the menstrual cycle and is the site of embryo implantation. The two fallopian tubes extend laterally from the uterine cornua to the ovaries; their fimbriated ends capture the ovum at ovulation and ciliary action transports it toward the uterus — fertilization normally occurs in the ampullary portion of the tube. The ovaries produce ova and secrete the sex steroids estrogen, progesterone, and testosterone.

Male External and Internal Anatomy

The penis contains three cylindrical bodies of erectile tissue: two corpora cavernosa arranged side by side and the corpus spongiosum, which surrounds the urethra and expands distally to form the glans. The glans is covered by the prepuce (foreskin) in uncircumcised males; the frenulum, on the ventral surface at the junction of the glans and shaft, is particularly sensitive. The scrotum is a pouch of skin containing the testes and epididymides; it maintains testicular temperature approximately 2°C below core body temperature, necessary for optimal spermatogenesis.

Each testis contains numerous seminiferous tubules in which spermatogenesis occurs; Leydig cells in the interstitial tissue produce testosterone in response to LH stimulation. The epididymis, a coiled tube on the posterior surface of the testis, is the site of sperm maturation and storage. From the epididymis, sperm travel through the vas deferens to the ejaculatory ducts, which pass through the prostate gland and open into the urethra. The seminal vesicles contribute fructose and prostaglandins to seminal fluid; the prostate contributes enzymes and a slightly alkaline fluid that protects sperm in the acidic vaginal environment; the bulbourethral (Cowper’s) glands secrete a clear pre-ejaculatory fluid that neutralizes urethral acidity before ejaculation.

The Menstrual Cycle

The menstrual cycle is a recurring sequence of hormonal and anatomical changes preparing the uterus for potential pregnancy. Its regulation involves the hypothalamic–pituitary–ovarian axis.

Premenstrual syndrome (PMS) refers to cyclical physical and psychological symptoms occurring in the luteal phase and resolving with menstruation; its etiology is multifactorial, involving serotonergic and GABAergic systems as well as progesterone metabolites. Premenstrual dysphoric disorder (PMDD), characterized by severe mood disruption, is recognized in the DSM-5 and responds to SSRIs. Dysmenorrhea — painful menstruation due to prostaglandin-mediated uterine contractions — is the most common gynaecological complaint and is effectively treated with NSAIDs.

Chapter 4: Sexual Arousal and Response

Masters and Johnson’s Four-Stage Model

The foundational laboratory research of William Masters and Virginia Johnson provided the first systematic description of the physiological changes accompanying sexual arousal and orgasm. Their four-stage model remains the most widely taught framework and is the basis for clinical classification of sexual dysfunctions in the DSM system.

During the excitement phase, the central physiological events are vasocongestion (engorgement of blood vessels in the pelvic region and genitals) and myotonia (generalized increase in muscular tension). In women, vaginal transudation — the seeping of fluid through the vaginal walls due to pelvic vasocongestion — produces lubrication within seconds of effective sexual stimulation. The clitoris engorges and increases in diameter; the labia minora darken and expand; the inner two-thirds of the vagina lengthen and widen (tenting effect); the uterus elevates. In men, reflexive penile erection occurs through a vascular mechanism: parasympathetic neural input releases nitric oxide (NO) in penile vascular tissue, activating guanylyl cyclase to produce cGMP, which relaxes smooth muscle in the corpora cavernosa, allowing blood influx. Scrotal thickening and testicular elevation also begin.

The plateau phase represents an intensification and consolidation of excitement-phase changes. In women, the outer third of the vagina engorges to form the orgasmic platform; the clitoris retracts under the clitoral hood. In men, the testes elevate further and increase in size; Cowper’s gland secretions may appear at the urethral meatus. Heart rate, blood pressure, and respiratory rate continue to rise throughout plateau.

Orgasm is characterized by the rhythmic contraction of perineal muscles, the uterus and vagina (in women), and the ejaculatory ducts, seminal vesicles, prostate, and bulbocavernosus muscles (in men) at approximately 0.8-second intervals. Ejaculation consists of two phases: emission (delivery of seminal fluid to the posterior urethra) and expulsion (propulsive contractions forcing semen through the urethra). Orgasm is accompanied by intense subjective pleasure, altered consciousness, and autonomic discharge — tachycardia, hyperventilation, and a sex flush (vasocongestion of skin) in many individuals. Masters and Johnson demonstrated that female orgasm, regardless of whether it is achieved through vaginal penetration or direct clitoral stimulation, is physiologically identical — dismantling Freud’s clinically influential but scientifically unsupported clitoral/vaginal distinction.

Resolution is the gradual return to the unaroused state. Women lack an obligatory refractory period and may re-enter excitement directly after orgasm, enabling multiple orgasms. Men enter a refractory period of variable duration — from minutes in young men to hours in older men — during which further erection and orgasm are physiologically impossible.

Kaplan’s Three-Stage Model

Helen Singer Kaplan, a psychiatrist who integrated psychodynamic and behavioural perspectives, proposed a simplified three-stage model in her influential work The New Sex Therapy (1974). Kaplan argued that the critical clinical distinction was between sexual desire and the physiological phases of arousal and orgasm.

Basson’s Circular Model of Female Sexual Response

Rosemary Basson’s model, first published in 2000, challenged the assumption that the linear Masters and Johnson framework adequately described the sexual response of many women — particularly those in established relationships.

The Dual Control Model

John Bancroft and Erick Janssen at the Kinsey Institute proposed the Dual Control Model as a more granular account of individual variation in sexual arousability.

This model has important clinical implications: many sexual problems can be understood as excessive inhibition (SIS overactivity) rather than insufficient excitation, suggesting that treatment should focus on reducing inhibitory factors — anxiety, shame, negative cognitions — rather than simply attempting to increase stimulation. The model also explains individual differences in risk-taking sexual behaviour: individuals with high SES and low SIS may be more prone to sexual risk-taking in arousing contexts.

Hormonal Influences on Arousal

Testosterone is the primary hormonal driver of sexual desire in both men and women, acting centrally on dopaminergic systems to modulate libido. In men, testosterone is produced primarily by the Leydig cells of the testes under LH stimulation; in women, it is produced by the ovaries and adrenal cortex in smaller but functionally significant quantities. Androgen deprivation — whether from hypogonadism, surgical castration, or anti-androgen pharmacotherapy — produces marked reductions in sexual desire in both sexes. Estrogen supports vaginal lubrication and tissue integrity in women; its decline at menopause produces genitourinary syndrome of menopause (formerly called vulvovaginal atrophy), which can make intercourse painful and is associated with reduced genital responsiveness.

Chapter 5: Prenatal Development and Sexuality Across the Lifespan

Chromosomal and Hormonal Sex Differentiation

Human sexual differentiation proceeds through a series of sequential steps, each building on the last. The chromosomal sex established at fertilization (XX or XY) determines gonadal sex: the bipotential gonad, present in all embryos through approximately week six, differentiates into ovaries (XX, in the absence of SRY signalling) or testes (XY, triggered by SRY). Gonadal sex then determines hormonal sex, with the testes producing testosterone, DHT, and AMH that drive male anatomical differentiation. Anatomical sex — both internal and external — follows from hormonal sex. Finally, at puberty, hormonal sex activates the development of secondary sex characteristics.

Intersex Conditions

Congenital Adrenal Hyperplasia (CAH) results from a deficiency of the enzyme 21-hydroxylase, causing the adrenal glands to produce excessive androgens beginning prenatally. In 46,XX individuals, this produces virilization of the external genitalia to varying degrees, while internal female structures (uterus, ovaries) remain intact. Research on women with CAH has found elevated rates of bisexual and lesbian identity and more male-typical profiles on certain spatial and play-behaviour measures, providing some support for prenatal androgen influences on brain organization — though effect sizes are modest and data are complex.

Androgen Insensitivity Syndrome (AIS) occurs in 46,XY individuals whose cells have a non-functional androgen receptor. In complete AIS (CAIS), testosterone and DHT cannot act on target tissues, and the individual develops female-appearing external genitalia despite having a 46,XY karyotype and undescended testes. The Müllerian structures regress (due to intact AMH production), so there is no uterus, but a short vaginal pouch is present. Individuals with CAIS are typically raised as girls, have unambiguous female gender identity, and are generally attracted to men. Partial AIS (PAIS) produces intermediate phenotypes.

Sexuality in Childhood and Adolescence

Children are not asexual; they are sexual beings from birth, though the nature of childhood sexuality differs fundamentally from adult sexuality. Infant males have erections during REM sleep and in response to genital stimulation; infant females have vaginal lubrication. Toddlers discover genital self-stimulation and may continue it for sensory pleasure. School-age children engage in sex play — examining each other’s genitals, playing “doctor” — as a normal exploratory behaviour that does not predict adult psychopathology. Children develop gender constancy (the understanding that gender is stable over time and situations) between ages 3 and 6.

Puberty is the developmental transition in which the body matures reproductively under the influence of gonadal hormones. It is initiated by the hypothalamic pulse generator increasing its secretion of GnRH, which drives pituitary secretion of FSH and LH, which in turn stimulate gonadal hormone production. In girls, the first visible sign is typically thelarche (breast bud development), followed by pubic hair, the adolescent growth spurt, and menarche (average 12.4 years in Canada). In boys, testicular enlargement precedes penile growth, pubic hair, and voice deepening. Spermarche (first ejaculation, usually experienced as a nocturnal emission) typically occurs around age 12–14.

Adolescence is the developmental period during which sexual identity formation becomes a central psychological task. For sexual minority youth, this process includes the additional challenge of coming out — disclosing a lesbian, gay, or bisexual identity to self and others. Models by Vivienne Cass and Richard Troiden describe stages from identity confusion through identity synthesis, though contemporary models emphasize that these stages are neither invariant nor universal. Sexual minority youth face elevated rates of depression, anxiety, and suicidality; family acceptance is the single strongest protective factor.

Sexuality in Adulthood and Older Age

Adult sexuality encompasses a broad range of behaviour, attitude, and relational configuration. Longitudinal data from the National Survey of Sexual Health and Behavior (Herbenick et al.) document that sexual activity patterns are highly diverse and change substantially across the life course. Young adulthood is typically a period of exploratory partnering; mid-life often involves shifts in relationship context, partner stability, and sexual frequency. In older adulthood, sexual activity typically changes rather than ceases. Physiological changes affect sexual response: men require more direct stimulation to achieve erection and experience longer refractory periods; women experience vaginal thinning and reduced lubrication due to declining estrogen. Both of these changes are addressable with appropriate pharmacological and behavioural intervention. Research consistently finds that individuals who had active and satisfying sex lives in younger adulthood tend to maintain sexual interest and activity into later life, and that relational quality is the strongest predictor of sexual satisfaction at all ages.

Chapter 6: Attraction, Love, and Relationships

Theories of Interpersonal Attraction

Why do people become attracted to specific others? Social psychologists have identified several robust determinants. Proximity — mere physical closeness — is among the most powerful; people are far more likely to form relationships with those they encounter regularly. The mere exposure effect (Zajonc) demonstrates that repeated exposure to a stimulus increases liking, partly explaining why proximity matters. Similarity — in values, attitudes, interests, and background — predicts both initial attraction and long-term relationship satisfaction. The matching hypothesis suggests that people tend to pair with others of approximately equal perceived physical attractiveness.

Physical attractiveness exerts consistent and powerful effects on social outcomes. Cross-cultural research identifies certain features as broadly attractive: facial symmetry (thought to signal developmental stability), waist-to-hip ratio in women, and facial features influenced by sex hormones. Evolutionary psychology interprets these findings as cues to mate quality — symmetry signals developmental health; the waist-to-hip ratio correlates with fertility. However, evolutionary explanations are often post-hoc and underweight the role of cultural variation in beauty standards, which are substantial. Preference for attractiveness features also shifts with hormonal context, ovulatory cycle phase, and life history.

Attachment Theory and Romantic Relationships

John Bowlby’s attachment theory, originally developed to explain the infant–caregiver bond, has been extensively applied to adult romantic relationships by Cindy Hazan and Phillip Shaver and elaborated by Kim Bartholomew into a two-dimensional model.

Attachment security predicts relationship satisfaction, constructive conflict resolution, sexual satisfaction, and resilience following relationship dissolution. Attachment anxiety is associated with hypervigilance to partner cues; attachment avoidance is associated with emotional withdrawal and suppression of intimacy needs. Both insecure styles predict lower sexual satisfaction through different mechanisms — anxious attachment through intrusive sexual monitoring and performance anxiety, avoidant attachment through emotional distancing during intimacy.

Sternberg’s Triangular Theory of Love

Robert Sternberg proposed one of the most widely cited models of love in his Triangular Theory (1986), in which all forms of love are constituted by varying combinations of three components.

Passion tends to diminish with habituation in long-term relationships through a process of hedonic adaptation, while intimacy and commitment often deepen over time. Maintaining passion in long-term relationships is associated with novel and arousing shared activities (Aron et al., “self-expansion” model) rather than familiar, comfortable ones.

Relationship Diversity

Monogamy — romantic and sexual exclusivity within a dyadic relationship — is the culturally normative relationship structure in contemporary Western societies, though anthropological evidence indicates that lifetime serial monogamy rather than strict lifetime pair-bonding describes actual behaviour more accurately. Consensual non-monogamy (CNM) refers to relationship configurations in which all parties have explicit knowledge of and agreement to the non-exclusive nature of the relationship. Polyamory — maintaining multiple emotionally intimate and romantic relationships simultaneously — is one form of CNM. Open relationships, swinging, and relationship anarchy are others.

Research comparing CNM and monogamous individuals finds no consistent differences in relationship satisfaction, psychological well-being, or ability to manage jealousy; CNM couples do report more explicit communication about needs and boundaries, which some researchers interpret as a protective factor. Relationship dissolution is among the most stressful life events most people encounter. John Gottman’s longitudinal research identified four communication patterns — criticism, contempt, defensiveness, and stonewalling (the “Four Horsemen”) — as particularly predictive of dissolution, with contempt (communicating moral superiority toward one’s partner) the single strongest predictor.

Chapter 7: Sexual Behaviour and Fantasy

Masturbation

Masturbation — self-stimulation of the genitals for sexual pleasure — is among the most universally practiced sexual behaviours, yet it remains one of the most culturally loaded. Despite the long history of medical and religious condemnation reviewed in Chapter 1, contemporary sexology regards masturbation as a normal and potentially beneficial behaviour across all ages and relationship statuses. National survey data consistently find lifetime prevalence rates of approximately 92–95% in men and 70–80% in women, with substantial variation by age, religiosity, and cultural background.

Masturbation serves multiple psychological functions beyond simple sexual release. It is a mode of self-exploration that enables individuals to learn about their own sexual responses, a finding with direct therapeutic relevance — directed masturbation is the first-line treatment for female orgasmic disorder. Masturbation is used as stress reduction; it continues alongside partnered sexual activity in most relationships without displacing it; and in some research it is positively associated with partnered sexual satisfaction. Clinical concern is warranted only in presentations where masturbation causes significant distress, occupational impairment, or relationship damage.

Oral Sex and Partnered Behaviours

Oral sex — cunnilingus (oral stimulation of the female genitalia) and fellatio (oral stimulation of the penis) — has become normative among adolescent and adult populations in most Western countries. NSSHB data show that 70–80% of respondents in younger age cohorts have engaged in oral sex, and qualitative research suggests it is increasingly framed as an ordinary component of sexual repertoires. Anilingus (oral stimulation of the anus) remains less common but is practiced across genders and orientations. Oral sex carries lower but non-negligible STI transmission risk compared to penetrative intercourse; barrier methods (dental dams, condoms) reduce this risk.

Sexual intercourse — the insertion of the penis into the vagina — remains the most culturally privileged form of sexual activity in heterosexual contexts, yet the equation of “sex” with vaginal penetration reflects heteronormative assumptions and systematically obscures the sexual experiences of same-sex couples and individuals for whom intercourse is unavailable or undesirable. Research suggests that positions enabling simultaneous clitoral stimulation are more reliably associated with female orgasm, consistent with the anatomical primacy of the clitoris discussed in Chapter 3.

Sexual Fantasy

Sexual fantasy — internally generated mental imagery with erotic content — is nearly universal. Survey research finds that more than 95% of both men and women report sexual fantasies, occurring during masturbation, partnered sex, and spontaneously at other times. Common fantasy themes include activities with a current or past partner, encounters with a novel partner, group sex, scenarios involving dominance or submission, and voyeuristic elements. Gender differences in fantasy content are documented, though they are often overstated; men report more visual and partner-varied content on average, while women report more emotionally contextualized and narrative content — though these are distributional differences with substantial overlap.

Sexual Scripts Theory

William Simon and John Gagnon introduced sexual scripts theory in the 1970s as a sociological framework for understanding how sexual behaviour is socially organized. Scripts operate at three levels: cultural scenarios (the macro-level shared cultural narratives about appropriate sexuality), interpersonal scripts (the interactive scripts guiding how individuals present and respond in sexual encounters), and intrapsychic scripts (the inner narrative an individual uses to organize desire and fantasy). Scripts are learned through socialization and media, and they shape what people recognize as sexual, what they consider appropriate, and how they interpret others’ cues. Divergence between partners’ scripts — about whether a given behaviour is on the table, who initiates, what counts as sex — is a major source of sexual miscommunication and dissatisfaction. Hookup culture among college students can be understood as a scripted set of norms about casual sexual encounters that coexist with, and sometimes conflict with, more traditional relationship scripts.

Chapter 8: Sexual Dysfunctions

Classification and Prevalence

Sexual dysfunctions are characterized by clinically significant disturbances in an individual’s ability to experience sexual desire, arousal, or orgasm, or by pain associated with sexual activity. The DSM-5 reorganized the classification substantially from previous editions, creating gender-specific diagnoses for many conditions and requiring that symptoms be present for approximately six months, occur on most or all occasions of sexual activity, and cause significant personal distress. The distress criterion is critical: a mismatch between partners’ desired frequency does not constitute a dysfunction in either partner in the absence of individual distress.

Prevalence estimates depend heavily on definition and measurement but are substantial: approximately 30–40% of women and 20–30% of men report some sexual difficulty at any given time, though rates of clinically significant, distress-associated dysfunction are considerably lower. Sexual dysfunctions are best understood within the biopsychosocial model as the products of biological, psychological, and relational factors in interaction, with the relative weight of each domain varying across disorder type and individual presentation.

Desire and Arousal Disorders

Erectile Disorder (ED) — difficulty achieving or maintaining an erection sufficient for satisfying sexual activity — affects approximately 10–20% of men across age groups, with prevalence increasing steeply with age. Biological causes include cardiovascular disease (endothelial dysfunction), diabetes mellitus (vascular and neurological complications), hypogonadism, and medication side effects (especially antihypertensives and SSRIs). Psychological causes include performance anxiety, depression, and relationship conflict. The primacy of biological versus psychological factors can often be assessed by whether nocturnal penile tumescence (erections during REM sleep) is preserved; intact nocturnal erections suggest psychological rather than organic etiology.

Orgasm Disorders

Female Orgasm Disorder is diagnosed in women who experience significant delay, infrequency, or absence of orgasm despite adequate arousal and stimulation, causing distress. Approximately 10% of women report never having experienced orgasm; the majority of anorgasmic women are able to reach orgasm with adequate clitoral stimulation, suggesting that the “problem” often lies partly in sexual technique and the cultural script privileging vaginal penetration. Directed masturbation training — in which the woman learns to bring herself to orgasm through self-stimulation — has the highest efficacy of any treatment for primary anorgasmia.

Delayed Ejaculation — persistent difficulty achieving ejaculation despite adequate arousal — can be caused by idiosyncratic masturbatory styles that do not generalize to partnered sex, medication effects (especially SSRIs), or psychological factors. Premature (Early) Ejaculation is the most common male sexual dysfunction, affecting approximately 20–30% of men; ejaculation occurs within approximately one minute of penetration, before the individual wishes it. Biological (penile hypersensitivity, serotonin transporter gene variants) and psychological (anxiety, conditioned rapid ejaculation) factors both contribute.

Genito-Pelvic Pain and Penetration Disorder

Treatments for Sexual Dysfunction

Sensate focus, developed by Masters and Johnson, is a structured set of non-demand touch exercises that couples perform sequentially, beginning with non-genital touching and progressing toward genital and eventually sexual contact, with the explicit prohibition of intercourse until later stages. It interrupts performance anxiety by redirecting attention from goal-oriented sexual activity to present-moment sensory experience. Cognitive-Behavioural Therapy (CBT) addresses dysfunctional beliefs (e.g., “I must achieve erection or I am a failure”), anxiety-management techniques, and sexual skills training.

Chapter 9: Paraphilic Disorders and Sexual Variations

Paraphilia versus Paraphilic Disorder

A fundamental and clinically important distinction in the DSM-5 is between a paraphilia and a paraphilic disorder. A paraphilia is an intense and persistent sexual interest in atypical objects, situations, or individuals. A paraphilic disorder is a paraphilia that causes significant distress to the individual or involves harm or risk of harm to others.

Specific Paraphilic Disorders

Voyeuristic Disorder involves sexual arousal from observing an unsuspecting individual, typically undressed or engaged in sexual activity. It is distinguished from consensual observation in contexts such as pornography; the arousal is specifically linked to the target’s non-consent. Exhibitionistic Disorder involves sexual arousal from exposing one’s genitalia to an unsuspecting person and is among the most common paraphilic disorders presenting to clinical and forensic settings.

Fetishistic Disorder involves intense sexual arousal to nonliving objects (shoes, underwear, rubber garments) or highly specific body parts (partialism). Conditioning theories propose that fetishes develop when neutral stimuli are repeatedly paired with sexual arousal during masturbation; consistent with this, fetishes most often involve objects associated with early sexual experiences or with the body. Transvestic Disorder is diagnosed in heterosexual men who experience distress or functional impairment from cross-dressing for sexual arousal. It must be distinguished from transgender identity, which is not a paraphilia, and from non-distressing cross-dressing, which does not constitute a disorder.

Sexual Sadism Disorder involves sexual arousal from the physical or psychological suffering of a nonconsenting person. Sexual Masochism Disorder involves sexual arousal from being humiliated, beaten, or made to suffer, and is a disorder only when causing significant distress or impairment. Consensual BDSM (bondage, discipline, dominance, submission, sadism, masochism) between informed adult partners is not a disorder.

Pedophilic Disorder involves sexual attraction to prepubescent children (typically under age 13) in an individual who is 16 or older and at least five years older than the child. It is important to distinguish the paraphilic attraction from child sexual abuse (CSA), which is behaviour; not all individuals with pedophilic attraction act on it. Cognitive distortions minimizing harm to children are a central target of treatment, which typically combines CBT with anti-androgen pharmacotherapy to reduce sexual drive.

Theories of Paraphilic Etiology

Multiple theories have been proposed, none fully adequate. Conditioning and learning accounts emphasize the pairing of early sexual arousal with atypical stimuli. Courtship disorder theory (Freund and Blanchard) proposed that exhibitionism, voyeurism, frotteurism, and rape share a common etiology as distortions of normal four-stage courtship behaviour. Neurobiological accounts have found elevated rates of paraphilias associated with conditions affecting temporal lobe function and with anomalous connectivity between cortical representation areas of the genitals and adjacent body parts (potentially explaining proximity-based fetishes such as foot fetishism). Developmental trauma accounts propose links between childhood sexual abuse and later paraphilic development, though the majority of individuals with a history of CSA do not develop paraphilias.

Chapter 10: Sexual Consent, Violence, and Sexual Health

Consent: Definitions and Communication

Sexual consent is the freely given, reversible, informed, enthusiastic, and specific agreement to engage in sexual activity. Contemporary consent education emphasizes that consent must be affirmative — requiring the presence of a “yes” rather than merely the absence of a “no” — ongoing (not established once and then assumed to continue), and revocable at any time. Consent cannot be given by individuals who are incapacitated by alcohol or drugs, under the age of legal consent, or under conditions of coercion, threats, or undue authority relationships.

Sexual Coercion and Rape Myths

Sexual violence encompasses rape, sexual assault, and sexual coercion — a spectrum of behaviours involving sexual contact without consent. Lifetime prevalence estimates from national surveys indicate that approximately 1 in 3–4 women and 1 in 6–10 men experience sexual assault over their lifetime; these estimates are likely underestimates given well-documented underreporting due to shame, fear of disbelief, and distrust of legal institutions. The majority of perpetrators are known to their victims; intimate partner sexual assault is common and particularly underreported.

Feminist theories of sexual violence frame it not as aberrant individual behaviour but as an expression of patriarchal power structures that eroticize dominance and construct masculine entitlement to sexual access. Integrated ecological models — such as the ecological framework of Heise, and Koss’s Confluence Model for perpetration — recognize individual (e.g., hostile masculinity beliefs, antisocial personality features), relational (e.g., peer norms supporting coercion, relationship power imbalance), community (e.g., poverty, norms of masculinity), and societal (e.g., gender inequality, legal frameworks) risk factors as interacting.

Consequences of Sexual Violence

The psychological consequences of sexual assault are substantial and varied. Post-Traumatic Stress Disorder (PTSD) occurs in 30–50% of sexual assault survivors. Symptoms include intrusive re-experiencing of the assault (flashbacks, nightmares), avoidance of trauma-related stimuli, negative alterations in cognition and mood (including trauma-related guilt and self-blame), and hyperarousal. Depression, anxiety disorders, substance abuse, and suicidality are also significantly elevated following assault.

Sexually Transmitted Infections: Epidemiology and Biology

Sexually transmitted infections (STIs) remain among the most prevalent infectious diseases globally, and rates of bacterial STIs in Canada and the US have been rising for over a decade. STIs are infections whose primary route of transmission is sexual contact, though some (HIV, hepatitis B, herpes) can also be transmitted through blood, vertical transmission, or other routes. The preferred term is “infection” rather than “disease” because many infections are asymptomatic.

HIV/AIDS deserves particular elaboration. HIV attacks CD4+ T lymphocytes, progressively impairing cellular immunity. Transmission occurs through receptive anal intercourse (highest risk per act), vaginal intercourse, sharing of injection equipment, and vertical transmission. Antiretroviral therapy (ART) now suppresses HIV viral load to undetectable levels; individuals on effective ART are Undetectable = Untransmittable (U=U) — they cannot sexually transmit the virus to partners. This finding has transformed HIV prevention, reducing stigma and providing a powerful treatment-as-prevention strategy.

HPV vaccination with the nonavalent vaccine (Gardasil 9) protects against nine HPV strains including the two highest-risk oncogenic strains (16 and 18, responsible for approximately 70% of cervical cancers) and two strains causing genital warts. Canadian national immunization programs offer HPV vaccination to all adolescents regardless of gender. Cervical cancer screening via Pap smear and HPV co-testing remains important even among vaccinated individuals because not all oncogenic strains are covered.

Sexual Health Frameworks and Prevention

The World Health Organization defines sexual health as “a state of physical, emotional, mental and social well-being in relation to sexuality; it is not merely the absence of disease, dysfunction or infirmity.” This positive framing — emphasizing well-being and not merely the absence of pathology — represents an important conceptual shift from the deficit-focused medical model. Harm reduction approaches accept that individuals will engage in sexual behaviour and aim to reduce associated risks rather than demanding abstinence. Barrier methods — male and female condoms, dental dams — remain highly effective against bacterial STIs and provide meaningful (though imperfect) protection against viral STIs. Consistent and correct condom use reduces HIV transmission risk per act by approximately 80–95%.

Chapter 11: Contraception and Reproductive Technologies

A Brief History of Contraception

The desire to control fertility is among the oldest documented human concerns. Ancient Egyptian papyri describe pessaries made of crocodile dung and honey inserted vaginally to block sperm; Greek and Roman texts record the use of plant-derived abortifacients and barrier devices. For most of recorded history, however, contraceptive knowledge was fragmentary, unreliable, and transmitted informally — often among women, outside the sphere of official medicine. The criminalization of contraceptive information in the nineteenth and early twentieth centuries (the Comstock laws in the United States, similar statutes in Canada and Britain) reflected anxieties about declining birth rates among the white middle class and about women’s sexual autonomy more broadly.

Margaret Sanger in the United States and Marie Stopes in Britain were pivotal figures in the early birth control movement, opening clinics, distributing information, and challenging legal prohibitions. In Canada, the dissemination of contraceptive information was a Criminal Code offence until 1969, when the Omnibus Bill (C-150) under Pierre Trudeau decriminalized both contraception and homosexuality. The development of the oral contraceptive pill — approved by the FDA in 1960 and available in Canada shortly thereafter — is widely regarded as one of the most consequential medical innovations of the twentieth century, enabling women to separate sexual activity from reproduction with unprecedented reliability.

Hormonal Methods

Hormonal contraceptives work primarily by suppressing ovulation through the administration of synthetic estrogen and/or progestin. The combined oral contraceptive pill (COC) contains both ethinyl estradiol (or a newer estrogen such as estetrol) and a progestin. It suppresses the hypothalamic–pituitary–ovarian axis, preventing the LH surge that triggers ovulation, while also thickening cervical mucus to impede sperm transport and thinning the endometrium. With perfect use, COCs have a failure rate of approximately 0.3% per year; with typical use — accounting for missed pills, late starts, and drug interactions — the failure rate rises to roughly 7–9%.

The progestin-only pill (POP, or “mini-pill”) contains no estrogen and is suitable for individuals who cannot tolerate estrogen (e.g., those with a history of migraine with aura, certain cardiovascular risk factors, or who are breastfeeding). Traditional POPs required very strict timing; newer formulations containing desogestrel or drospirenone offer a wider window and more reliably suppress ovulation. Other hormonal delivery systems include the transdermal patch (Evra), which is applied weekly and delivers estrogen and progestin through the skin; the vaginal ring (NuvaRing), inserted for three weeks per cycle; and injectable medroxyprogesterone acetate (Depo-Provera), administered every 12 weeks. Each has its own profile of benefits, side effects, and adherence requirements. The hormonal implant (Nexplanon), a progestin-releasing rod inserted subdermally in the upper arm, provides highly effective contraception for up to three years with a failure rate below 0.1%; it is widely used internationally but has had limited availability in Canada.

Barrier Methods

Barrier methods physically prevent sperm from reaching the ovum. The male (external) condom, typically made of latex, polyurethane, or polyisoprene, is the most widely used barrier method worldwide. When used correctly and consistently, condoms have a perfect-use failure rate of approximately 2% and a typical-use failure rate of about 13%. Critically, condoms are the only contraceptive method that simultaneously provides significant protection against sexually transmitted infections (STIs), making them indispensable in dual-protection strategies.

The female (internal) condom is a polyurethane or nitrile pouch inserted into the vagina before intercourse, with a flexible ring at each end. It is less widely used than the male condom and has somewhat higher typical-use failure rates (approximately 21%), but it offers the advantage of being controlled by the receptive partner and providing some protection to external genital skin. Diaphragms and cervical caps are dome-shaped devices placed over the cervix and used with spermicide; they are less effective than hormonal methods and have largely fallen out of common clinical use, though they remain an option for individuals seeking non-hormonal, user-controlled contraception. Spermicides used alone (typically nonoxynol-9) have high failure rates and can irritate vaginal and rectal mucosa, potentially increasing STI risk.

Intrauterine Devices

Intrauterine devices (IUDs) are small T-shaped devices inserted into the uterine cavity by a healthcare provider. They are among the most effective reversible contraceptive methods available, with failure rates below 1% for both typical and perfect use. Two main types exist. The copper IUD (e.g., Flexi-T, Mona Lisa in Canada) releases copper ions that are toxic to sperm and create an inflammatory reaction in the endometrium that prevents implantation; it contains no hormones and can remain effective for five to ten years depending on the model. The hormonal IUD (e.g., Mirena, Kyleena) releases levonorgestrel locally, thickening cervical mucus and thinning the endometrium; it often reduces or eliminates menstrual bleeding and is effective for five to eight years.

Permanent Methods

Tubal ligation involves surgical occlusion or removal of the fallopian tubes, preventing the ovum from reaching the uterus. It is typically performed laparoscopically and is considered a permanent procedure, though surgical reversal is sometimes possible with variable success. Vasectomy involves cutting or occluding the vas deferens, preventing sperm from entering the ejaculate. It is an outpatient procedure performed under local anaesthesia, is simpler and carries fewer risks than tubal ligation, yet is less commonly chosen — a disparity attributed to gendered norms about reproductive responsibility. Post-vasectomy semen analysis is required to confirm azoospermia before relying on the method.

Emergency Contraception

Emergency contraception (EC) refers to methods used after unprotected intercourse to prevent pregnancy. The most widely available is levonorgestrel (Plan B), a progestin-only pill effective when taken within 72 hours of intercourse (with diminishing efficacy thereafter). It primarily delays or inhibits ovulation and does not disrupt an established pregnancy. Ulipristal acetate (ella) is a selective progesterone receptor modulator effective up to 120 hours post-intercourse, with more consistent efficacy in that extended window and among individuals with higher body weight. The copper IUD, inserted within five days of unprotected intercourse, is the most effective form of emergency contraception (failure rate below 0.1%) and provides ongoing contraception thereafter.

Fertility Awareness and Withdrawal

Fertility awareness-based methods (FABMs) involve tracking physiological indicators — basal body temperature, cervical mucus consistency, cycle length — to identify the fertile window and abstaining from intercourse (or using barriers) during that period. With perfect use, symptothermal methods have failure rates of approximately 0.4–5%, but typical-use failure rates are considerably higher (12–24%), making FABMs less reliable than most hormonal and intrauterine methods. Modern cycle-tracking apps have increased interest in FABMs, though few have been clinically validated. Withdrawal (coitus interruptus) involves the male partner withdrawing the penis before ejaculation. Its typical-use failure rate is approximately 20%, reflecting the difficulty of consistent and timely execution as well as the presence of sperm in pre-ejaculatory fluid in some individuals.

Access and Equity in the Canadian Context

Contraceptive access in Canada is shaped by the absence of a national pharmacare programme. While some provinces and territories provide public coverage for certain contraceptives (British Columbia covers most prescription contraceptives for residents under 25; Ontario’s OHIP+ covers those under 25), many Canadians pay out of pocket or rely on employer insurance. Cost barriers disproportionately affect low-income, Indigenous, and rural populations. Over-the-counter availability of emergency contraception has improved access, but awareness gaps persist, and pharmacist gatekeeping remains an issue in some regions.

Assisted Reproductive Technologies

When contraception’s goal is reversed and individuals or couples seek to conceive, assisted reproductive technologies (ART) offer medical pathways. Intrauterine insemination (IUI) involves placing washed sperm directly into the uterine cavity around the time of ovulation; it is a relatively low-cost first-line treatment. In vitro fertilization (IVF) involves ovarian stimulation, oocyte retrieval, laboratory fertilization, and embryo transfer to the uterus; success rates vary by age and clinic but average approximately 30–40% per cycle for individuals under 35. Surrogacy — in which another person carries a pregnancy on behalf of the intended parent(s) — may be altruistic (legal in Canada under the Assisted Human Reproduction Act, 2004) or commercial (prohibited in Canada but legal in some other jurisdictions). Donor gametes and embryos raise complex ethical, legal, and psychological questions about identity, disclosure, and kinship.

Chapter 12: Conception, Pregnancy, and Childbirth

Fertilization and Early Development

Fertilization occurs when a single spermatozoon penetrates the oocyte, typically in the ampullary region of the fallopian tube. Of the approximately 200–300 million sperm deposited in the vagina during ejaculation, only a few hundred reach the vicinity of the ovum. Sperm must undergo capacitation — a series of biochemical changes in the female reproductive tract that enable the acrosome reaction, in which enzymes are released to digest the zona pellucida surrounding the oocyte. Once a single sperm fuses with the oocyte membrane, the cortical reaction alters the zona pellucida to prevent polyspermy. The resulting zygote contains 46 chromosomes — 23 from each parent — and the sex of the embryo is determined by whether the sperm carries an X or Y chromosome.

Over the next several days, the zygote undergoes mitotic division (cleavage) as it travels along the fallopian tube toward the uterus. By approximately day five, it has developed into a blastocyst — a hollow ball of cells comprising an outer layer (trophoblast, which will form the placenta) and an inner cell mass (which will become the embryo). Implantation in the uterine endometrium occurs approximately six to ten days after fertilization. The trophoblast secretes human chorionic gonadotropin (hCG), the hormone detected by pregnancy tests, which signals the corpus luteum to continue producing progesterone and maintain the endometrium.

The First Trimester (Weeks 1–12)

The first trimester is a period of extraordinary developmental change. By the end of the eighth week, the major organ systems have begun to form — a process called organogenesis — and the developing organism is reclassified from embryo to fetus. The neural tube, which will become the brain and spinal cord, closes by approximately day 28; failure of closure results in neural tube defects such as spina bifida. By week 12, the fetus is approximately 6 cm in length; the heart is beating, limbs are differentiated with fingers and toes, and external genitalia are beginning to differentiate.

For the pregnant individual, the first trimester is often marked by nausea and vomiting (“morning sickness,” though it can occur at any time of day), breast tenderness, fatigue, and urinary frequency. These symptoms are driven largely by rising hCG and progesterone levels. Miscarriage (spontaneous abortion) is most common during this period; approximately 15–20% of clinically recognized pregnancies end in miscarriage, most due to chromosomal abnormalities in the embryo.

The Second Trimester (Weeks 13–26)

The second trimester is often described as the most comfortable period of pregnancy. Nausea typically resolves, energy returns, and the pregnancy becomes visibly apparent. Fetal growth accelerates; by week 20, the fetus is approximately 25 cm long and weighs around 300 grams. Quickening — the first perception of fetal movement by the pregnant individual — usually occurs between weeks 16 and 22. The fetus develops lanugo (fine body hair), vernix caseosa (a waxy protective coating), and increasingly mature sensory capabilities; by the late second trimester, the fetus can hear sounds, including the pregnant individual’s voice and heartbeat.

Anatomical screening via ultrasound is typically performed around weeks 18–20, assessing fetal anatomy for structural abnormalities and, if desired, determining fetal sex. Prenatal genetic screening (e.g., non-invasive prenatal testing using cell-free fetal DNA in maternal blood) and diagnostic testing (amniocentesis, chorionic villus sampling) are offered based on risk factors and patient preference.

The Third Trimester (Weeks 27–40)

During the third trimester, the fetus gains weight rapidly, laying down subcutaneous fat that will assist in thermoregulation after birth. Lung maturation is a critical developmental milestone; surfactant production increases substantially after week 34, and fetuses born before this gestational age often require respiratory support. The fetus typically assumes a head-down (cephalic) presentation in preparation for birth. For the pregnant individual, the third trimester brings increasing physical discomfort: back pain, oedema, shortness of breath due to the expanding uterus compressing the diaphragm, and difficulty sleeping. Braxton Hicks contractions — irregular, non-progressive uterine contractions — become more noticeable and are distinct from true labour.

Prenatal Care and Teratogens

Regular prenatal care is associated with improved outcomes for both the pregnant individual and the fetus. Standard prenatal care in Canada includes monitoring blood pressure, weight gain, fundal height, and fetal heart rate; screening for gestational diabetes (typically at 24–28 weeks); screening for group B streptococcus (at 35–37 weeks); and blood tests for Rh factor, infections (HIV, hepatitis B, syphilis, rubella immunity), and anaemia.

Sexual Activity During Pregnancy

In the absence of specific medical contraindications (such as placenta previa, preterm labour risk, or premature rupture of membranes), sexual activity during pregnancy is generally safe and does not harm the fetus. Many couples experience fluctuations in sexual desire and activity across the trimesters. Some pregnant individuals report heightened arousal during the second trimester due to increased pelvic vasocongestion and hormonal changes, while others experience decreased desire related to fatigue, body image concerns, or physical discomfort. Open communication between partners about changing needs and comfort is important. Healthcare providers should proactively address sexuality during prenatal visits, as many patients are reluctant to raise the topic themselves.

Labour and Delivery

Labour is the process by which the fetus, placenta, and membranes are expelled from the uterus. It is conventionally divided into three stages. The first stage begins with the onset of regular, progressive uterine contractions and ends with complete cervical dilatation (10 cm). This stage is further divided into the latent phase (slow, early dilatation) and the active phase (more rapid dilatation). The second stage extends from complete dilatation to delivery of the infant; it involves active pushing by the birthing individual and typically lasts from minutes to a few hours. The third stage encompasses delivery of the placenta, usually within 30 minutes of birth.

Pain management during labour ranges from non-pharmacological approaches (movement, hydrotherapy, breathing techniques, continuous labour support) to pharmacological options. Epidural analgesia — injection of local anaesthetic and opioid into the epidural space of the lumbar spine — is the most effective form of labour pain relief and is widely used in Canada. It does not increase the rate of cesarean section but may prolong the second stage of labour.

The Postpartum Period

The postpartum period (puerperium) encompasses the six to eight weeks following delivery, during which the birthing individual’s body undergoes physiological recovery. The uterus involutes to its pre-pregnancy size, and lochia (postpartum vaginal discharge) gradually diminishes. Hormonal shifts — particularly the precipitous drop in estrogen and progesterone — can contribute to mood changes. Breastfeeding (lactation) is initiated by the hormones prolactin and oxytocin; colostrum, the initial breast secretion, is rich in antibodies and provides passive immunity to the newborn. The World Health Organization recommends exclusive breastfeeding for six months, with continued breastfeeding alongside complementary foods for two years or beyond.

Sexuality in the postpartum period is affected by physical recovery (perineal healing, vaginal dryness related to low estrogen, especially during breastfeeding), fatigue, body image adjustment, and the demands of newborn care. Most healthcare providers recommend waiting until after the postpartum checkup (typically six weeks) before resuming penetrative intercourse, though non-penetrative intimacy can resume earlier based on comfort. Research indicates that most couples resume sexual activity within two to three months postpartum, though desire and frequency may remain lower than pre-pregnancy levels for some time. Effective contraception should be discussed before hospital discharge, as ovulation can return within weeks of delivery, particularly in individuals who are not exclusively breastfeeding.

Chapter 13: Abortion

Legal Status in Canada

Canada occupies a unique position in global reproductive rights law: it has no criminal law restricting abortion at any gestational age. This legal landscape is the result of the landmark Supreme Court of Canada decision in R v. Morgentaler (1988), in which the Court struck down section 251 of the Criminal Code — which had permitted abortion only when approved by a hospital therapeutic abortion committee — as a violation of section 7 of the Canadian Charter of Rights and Freedoms (the right to life, liberty, and security of the person). The majority held that the existing law’s procedural requirements imposed delays, inconsistencies, and physical and psychological harm on women seeking abortion, thereby infringing their security of the person.

In practice, Canadian clinical guidelines (SOGC) recommend that abortion be available on request, with no gestational limit imposed by law. The vast majority of abortions in Canada occur in the first trimester; later abortions, which constitute a very small proportion, are typically performed for serious fetal anomalies or threats to the pregnant person’s health and are available only at a limited number of specialized facilities.

Methods of Abortion

Abortion procedures are classified as medication-based or procedural (surgical). Medication abortion uses a combination of mifepristone (an antiprogestin that blocks progesterone receptors, destabilizing the endometrium and detaching the embryo) and misoprostol (a prostaglandin analogue that induces uterine contractions and cervical softening). This regimen is approved in Canada for use up to nine weeks (63 days) of gestation (and is used off-label beyond this point in some settings). Mifepristone became available in Canada in 2017 under the brand name Mifegymiso, initially with restrictive dispensing requirements that were subsequently relaxed. The medication abortion is highly effective (95–98% complete abortion rate) and can be managed in primary care settings, expanding access beyond surgical facilities.

Both medication and procedural abortion are extremely safe. The risk of major complications from first-trimester abortion is less than 0.5%, and the mortality rate is lower than that of childbirth. Abortion does not increase the risk of breast cancer, infertility, or subsequent pregnancy complications — claims to the contrary, which have been propagated by anti-abortion organizations, are not supported by the scientific evidence.

Psychological Research

The psychological effects of abortion have been extensively studied. The most methodologically rigorous evidence comes from the Turnaway Study, a longitudinal project conducted by researchers at the University of California, San Francisco, which followed approximately 1,000 women who sought abortions — some who received them and some who were turned away because they had passed the gestational limit of their local facility. The study found that women who received wanted abortions did not experience elevated rates of depression, anxiety, PTSD, or substance use compared to those who were denied; in fact, being denied an abortion was associated with worse mental health outcomes in the short term, as well as greater economic hardship, lower educational attainment, and continued exposure to domestic violence.

The American Psychological Association’s Task Force on Mental Health and Abortion (2008) concluded that among adult women who have a single, elective, first-trimester abortion, the risk of mental health problems is no greater than the risk among those who carry an unintended pregnancy to term. The strongest predictor of negative post-abortion psychological outcomes is pre-existing mental health difficulty, not the abortion itself.

Ethical and Political Frameworks

The abortion debate is framed by two principal positions, though substantial variation exists within each. The anti-abortion (or “pro-life”) position generally holds that human life begins at conception and that the embryo or fetus possesses a right to life that supersedes the pregnant individual’s right to bodily autonomy. This position is often (though not exclusively) rooted in religious teachings, particularly Roman Catholic and evangelical Protestant theology. The pro-choice position holds that the pregnant individual has the right to make autonomous decisions about their own body and reproductive life, that personhood does not begin at conception, and that restricting access to safe abortion does not eliminate abortion but drives it underground, increasing morbidity and mortality.

Feminist scholarship emphasizes that abortion restrictions disproportionately affect marginalized populations — those who are low-income, racialized, rural, young, or otherwise lacking resources to circumvent barriers. The concept of reproductive justice, developed by women of colour activists in the United States (notably SisterSong Women of Color Reproductive Justice Collective), extends the analysis beyond individual “choice” to encompass the social conditions necessary for genuine reproductive autonomy: the right to have children, the right not to have children, and the right to parent children in safe and healthy environments.

Access Barriers in Canada

Despite the absence of criminal restrictions, access to abortion in Canada is uneven. Several provinces, particularly in Atlantic Canada and the Prairie provinces, have limited numbers of abortion providers; individuals in rural and northern communities may need to travel hundreds of kilometres to access services. Prince Edward Island did not have a local surgical abortion provider until 2017, and residents previously had to travel to neighbouring provinces. Medication abortion has improved access in underserved areas, as it can be prescribed by any trained physician or nurse practitioner and dispensed through pharmacies, but awareness and training gaps remain. Anti-abortion harassment at clinics — including protests, blockades, and targeted harassment of providers — has led to the passage of bubble zone legislation in several provinces, creating buffer zones around clinics and providers’ residences.

Global Comparative Context

Globally, approximately 73 million induced abortions occur annually, and roughly 45% of all abortions worldwide are classified by the WHO as “unsafe” — disproportionately in countries with restrictive abortion laws. The evidence is clear that legal restrictions do not reduce abortion rates; countries with the most restrictive laws (in parts of sub-Saharan Africa and Latin America) have abortion rates comparable to or higher than those in countries where abortion is broadly legal. What restrictions do reduce is the safety of abortion. Unsafe abortion is a leading cause of maternal mortality worldwide, responsible for approximately 4.7–13.2% of maternal deaths. The trend in recent decades has been toward liberalization — Ireland repealed its constitutional abortion ban in 2018, Argentina legalized abortion in 2020 — though significant reversals have also occurred, most notably the US Supreme Court’s decision in Dobbs v. Jackson Women’s Health Organization (2022), which overturned Roe v. Wade and permitted individual states to ban or severely restrict abortion.

Chapter 14: Sex Work, Pornography, and the Sex Trade

Definitions and Terminology

The language used to describe the exchange of sexual services for compensation is politically and analytically significant. The term sex work — coined by activist Carol Leigh in the 1970s — emphasizes that the exchange of sexual services is a form of labour and positions those who engage in it as workers with agency and rights. By contrast, the term prostitution carries historical connotations of criminality, immorality, and victimhood. Academic and policy usage varies; this chapter uses “sex work” as the primary term while acknowledging that not all individuals involved in the sex trade identify as workers by choice. The broader term sex trade or sex industry encompasses a wide range of activities including in-person sex work (street-based, indoor, escort), exotic dancing, pornography performance, phone sex, webcam modelling, and online content creation (e.g., subscription platforms).

Historical Context

The exchange of sexual services for material compensation has existed across virtually all documented societies. In some ancient civilizations, temple-based sexual rituals involved women who occupied respected social positions; in medieval and early modern Europe, sex work was alternately tolerated and violently suppressed, often reflecting broader social anxieties about disease, public order, and female sexuality. The nineteenth-century regulatory approach — exemplified by Britain’s Contagious Diseases Acts (1864–1869), which subjected women suspected of sex work to compulsory medical examinations — prompted feminist opposition from Josephine Butler and others, who argued that the laws punished women while ignoring male clients. This early feminist critique established arguments that resonate in contemporary debates.

In Canada, sex work has never been explicitly illegal per se, but a constellation of Criminal Code offences — communicating for the purpose of prostitution, keeping a common bawdy-house, living on the avails of prostitution — effectively criminalized most aspects of the trade. These provisions were challenged in the landmark Supreme Court of Canada case Canada (Attorney General) v. Bedford (2013), in which the Court unanimously struck down three prostitution-related Criminal Code provisions as violations of sex workers’ security of the person under section 7 of the Charter.

Legal Models

Four principal legal frameworks govern sex work internationally, each reflecting different assumptions about the nature of the trade.

Canadian Law: The PCEPA

In response to the Bedford decision, the Harper government enacted the Protection of Communities and Exploited Persons Act (PCEPA) in 2014, adopting a framework closely modelled on the Nordic model. The PCEPA criminalizes the purchase of sexual services (section 286.1), advertising the sale of sexual services (section 286.4), receiving material benefit from sex work in most circumstances (section 286.2), and procuring (section 286.3). The sale of one’s own sexual services is not itself an offence, though communicating for that purpose in certain public places near schools, daycares, or religious institutions is criminalized (section 213(1.1)). The stated legislative objectives are to reduce demand, protect communities, and assist sex workers in exiting the trade.

Pornography

Pornography — sexually explicit material produced for the purpose of sexual arousal — is a vast global industry, transformed by the internet from a niche market into an omnipresent cultural phenomenon. Estimates of the online pornography industry’s economic value vary widely but reach into the tens of billions of dollars annually. Pornography is legal in Canada provided that it does not depict minors, was produced with the consent of participants, and does not meet the legal threshold of obscenity as defined by the Supreme Court of Canada in R v. Butler (1992), which established a harm-based test centring on the degradation and dehumanization of individuals.

Research on the effects of pornography consumption is extensive but contested. Meta-analyses suggest modest correlations between pornography use and more permissive sexual attitudes, less relationship satisfaction among heavy users, and exposure to unrealistic depictions of bodies, sexual acts, and consent. However, establishing causality is methodologically difficult, and many observed correlations are small and influenced by confounding variables. Concerns about adolescent pornography exposure focus on the potential for pornography to serve as de facto sex education in the absence of comprehensive alternatives, normalizing aggressive or coercive sexual scripts and unrealistic body standards.

Sex Trafficking and Consensual Sex Work

A critical distinction in both scholarship and policy is that between sex trafficking — the recruitment, transportation, or harbouring of persons through force, fraud, or coercion for the purpose of sexual exploitation — and consensual adult sex work. Sex trafficking is a serious criminal offence under both Canadian law (Criminal Code, sections 279.01–279.04) and international law (the Palermo Protocol, 2000). Conflation of trafficking with all sex work has been criticized by researchers and sex worker organizations as empirically inaccurate and politically motivated, serving to justify the criminalization of consensual sex work under the guise of anti-trafficking measures.

Research on sex trafficking is complicated by definitional inconsistencies, political pressures, and methodological challenges. Widely cited estimates of trafficking prevalence have been criticized for lacking empirical basis. What is clear is that vulnerability to trafficking is strongly associated with structural factors — poverty, migration status, colonialism, racism, and gender inequality — and that effective anti-trafficking responses must address these root causes rather than relying solely on criminal law enforcement, which often harms the individuals it purports to protect.

Harm Reduction and Contemporary Issues

Harm reduction in the context of sex work refers to policies and programmes that accept the existence of sex work and aim to reduce associated health, safety, and legal risks. Examples include the provision of condoms and safer-sex supplies, occupational health and safety information, legal aid, drop-in centres, and “bad date” lists that allow sex workers to share information about dangerous clients. In Canada, organizations such as PEERS (Victoria), PACE Society (Vancouver), and Stella (Montreal) provide harm reduction services alongside advocacy.

Technology has profoundly reshaped the sex industry. Online platforms enable sex workers to advertise, screen clients, and work indoors — generally safer than street-based work — but also create new vulnerabilities including digital surveillance, non-consensual sharing of images, platform censorship (as occurred with the passage of FOSTA-SESTA in the United States in 2018), and exploitation by platform operators. Subscription-based content platforms (such as OnlyFans) have enabled independent content creation but raise questions about labour conditions, platform power, and the blurring of boundaries between amateur and commercial pornography.

The study of sex work, like the study of sexuality more broadly, requires a willingness to engage with complexity, to resist moralizing simplifications, and to centre the voices and experiences of those most directly affected. The tension between protection and autonomy, between structural critique and individual agency, and between competing visions of sexual justice will continue to animate scholarship and policy in this field.

End of PSYCH 236 Course Notes — Winter 2026