Vector & Facial Geometry

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AU = Action Unit, the unit of Ekman & Friesen's Facial Action Coding System (1978): one named muscle movement, not an emotion. Structural terms describe bone or soft tissue that constrains how those movements read on a face.

The Less Masculine Man

Hormonal state, mate selection, and an unmeasured partner variable in postpartum psychosis

ABSTRACT

Research on hormonal contraception, human mate preference, and postpartum psychiatric illness has largely proceeded along separate tracks. Those literatures meet at one point that has not been treated as a variable. Several studies have reported that hormonal state is associated with women's preferences for masculine characteristics in men, including facial, vocal, physical, and behavioral traits. One study further reported that women using oral contraception when a relationship formed had partners with less masculine faces than women who were not using hormonal contraception at relationship formation. 1 Other work has associated changes in contraceptive status with changes in relationship satisfaction, although recent large studies, randomized evidence, and meta-analysis substantially qualify the strength and generality of those effects. 2

Separately, postpartum psychosis clusters around a period of profound reproductive endocrine change. Contemporary reviews increasingly treat susceptibility to reproductive hormonal change, rather than simply abnormal absolute hormone concentrations, as important in vulnerable women. 3

This article proposes the Less Masculine Man Hypothesis (LMMH): in a hormonally sensitive subset of women, a large reproductive-state transition may interact with characteristics of a male partner selected under a different hormonal state. Partner masculinity is not proposed as a cause of psychosis. It is proposed as an unmeasured moderator of relational perception, attraction, authority, and — where psychosis occurs — the phenomenology of internally generated voices.

That partner variable has not been measured systematically in the postpartum-psychosis literature. The hypothesis can be tested directly.

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Primer: Explanation Is Not Exculpation

STANDING NOTE ON SCOPE

This article does not argue that Lindsay Clancy is innocent.

A causal account of behavior and a judgment about responsibility are separate questions. Finding that hormones, psychiatric illness, mate selection, relationship structure, hallucinated voices, or altered perception contributed to an act does not erase agency, planning, knowledge, or responsibility.

Understanding mechanism is often most important when the conduct is grave.

The thesis here is not an insanity argument, a mitigation brief, or an attempt to convert explanation into absolution. Clancy's case is relevant because it concentrates behavioral, hormonal, relational, and phenomenological facts. Those facts can be studied without the conclusion that she lacked responsibility for what she did.

Prison exists in substantial part to incapacitate people who commit extraordinarily serious acts of violence. A person may be psychiatrically abnormal, hormonally destabilized, psychologically disordered, or influenced by internally generated commands and still present exactly the danger for which long-term confinement exists.

Mechanism matters. So does responsibility. The two questions should not be confused.

01 The Missing Man in a Disorder of Women

METHODOLOGICAL FRAME — variable identification; partner treated as measurand rather than context

Postpartum psychosis is conventionally studied through the patient: psychiatric history, reproductive history, sleep, medications, genetics, immune function, endocrine transition, symptoms, treatment, and outcome. Her partner usually enters the literature as caregiver, observer, source of social support, or victim of circumstances. Studies of partners describe shock, helplessness, hypervigilance, caregiving burden, changing family roles, and the task of recognizing deterioration. 4 (Holford et al., 2018, BMC Pregnancy & Childbirth)

Almost nobody has asked a more primitive question: what kind of man is he?

Not whether he is supportive. Not whether the marriage is happy. Not whether he recognizes symptoms quickly. Those are relationship variables.

The proposed variable is masculinity.

For this hypothesis, masculinity must be operational rather than rhetorical. It can include sexually dimorphic facial morphology, vocal fundamental frequency, shoulder and body morphology, physical strength, independently rated masculine appearance, perceived dominance, assertiveness, competitiveness, and validated behavioral ratings. It does not mean moral worth, sexual orientation, intelligence, kindness, paternal competence, or social value.

That distinction matters because the mate-selection literature already contains a surprising finding: hormonal state has, in some studies, been associated with precisely this dimension of male preference.

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02 Hormones Do Not Merely Regulate Fertility

The oral contraceptive pill changes reproductive endocrinology by suppressing the ordinary ovulatory cycle. It would be peculiar to assume in advance that its effects terminate at the ovaries.

Research has long examined whether reproductive hormonal variation affects attraction to sexually dimorphic male traits. Changes in preferences for male vocal masculinity have been associated with reproductive hormonal variation, and measured changes in estradiol have been reported to predict within-woman changes in preferences for masculine male voices. 5 (Puts, 2006, Human Nature 17:114)

The facial literature produced a more provocative result.

In 2013, Little and colleagues examined women initiating oral contraception and reported that initiation significantly decreased preference for masculine male faces. In a second component involving actual couples, male partners of women who reported using the pill when their relationships formed were judged and measured as having less masculine faces than partners selected by women who were not using hormonal contraception at relationship formation. 1 (Little et al., 2013, Psychoneuroendocrinology 38:1777)

The important feature of this finding is not merely altered attraction. It is downstream mate selection. The hormone-associated preference was reportedly visible in the man standing next to her.

Morphometrics of Facial Sexual Dimorphism & Expression Dynamics

The facial-feature research in these paradigms relies on geometric vector manipulations of sexually dimorphic traits. Computerized linear shape transforms isolate structural ratios driven by pubertal testosterone-to-estrogen balances:

These structural features are the same physical vectors used in early computerized facial-morphing studies and early 3D character design to establish instant visual cues of dominance versus submissiveness.

Static bony landmarks only establish the structural baseline. Integrating craniofacial dimorphism with Paul Ekman's Facial Action Coding System (FACS) maps those landmarks to dynamic muscle contractions. Craniofacial anatomy sets the foundation; Ekman's Action Units define the movement vectors across the features.

Theoretical Framework: Dimorphic Expression Dynamics

Static anatomy modifies dynamic expression in three ways:

Half-Life 2 provides a useful engineering demonstration of perceptual compression. Released by Valve in 2004, it is a first-person science-fiction game whose Source engine had to animate faces under tight real-time constraints: limited polygons, a small set of bones and flex controllers, and no photographic craniofacial scan of each character. Valve built that system on a FACS-derived action-unit logic. With a sparse set of geometric and muscular vectors, the faces could still convey recognizable differences in affect, dominance, tension, and social presentation. The point is not that a video game establishes craniofacial physiology. It is that a relatively sparse representation of facial structure and movement can preserve socially meaningful information. If low-resolution synthetic faces can communicate those distinctions, high-resolution human facial data should contain at least as much measurable signal.

A 2014 study approached the problem more broadly through a Partner's Masculinity Index. Measurements extended beyond a computerized male face to physical, psychological, status, competitiveness, and behavioral characteristics. Non-users of oral contraception scored higher than pill users in preference for the masculinity composite during the fertile portion of the natural cycle. 6 (Gori et al., 2014, J Sex Med 11:2181)

These findings establish a legitimate empirical question: whether endocrine state can alter selection pressure for masculine characteristics in a mate.

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Δpreference ∝ Δ[E₂]; within-woman estimate, f₀ stimuli

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03 Conflicting Results Define the Size of the Question

The literature does not produce a single effect estimate. It produces a sequence.

Early studies, including Little et al. (2013) and Gori et al. (2014), reported that oral-contraceptive use was associated with reduced preference for masculine male characteristics and, in Little's couple data, with less-masculine faces in the men actually selected. 1 6 Those papers are the empirical starting point of the LMMH.

Later work tested the same preference claim under tighter constraints. A 2019 comparison of 6,482 heterosexual women found no evidence that oral-contraceptive users had weaker preferences for masculine male faces. 7 Jones, Hahn and colleagues had already reported, in large longitudinal hormone work, no compelling evidence that facial-masculinity preferences tracked within-woman steroid change, and no evidence that oral-contraceptive use decreased those preferences. A preregistered double-blind randomized controlled trial published in 2025 likewise found no statistically significant causal effect of oral contraception on preferences for facial masculinity or symmetry; the trial could not exclude a small effect, but it did exclude a large one. 8 The 2025 RCT authors themselves framed the result as aligning with recent large-sample correlational work rather than with the early cycle-and-pill preference studies.

A 2025 meta-analysis of the related contraceptive-congruency literature found no significant pooled between-person association with sexual satisfaction; within-person analysis suggested only a small association. 9 That is a downstream-evaluation finding, not a facial-preference finding, but it belongs to the same later wave: average effects, if present, are small.

These papers do not merely "conflict." They mark a preference-based shift over time in what the evidence will support. The early claim was that hormonal state changes how women weight masculine traits. The later claim, from larger and more controlled preference designs, is that any such weighting change is not a reliable population-level effect on facial masculinity or symmetry.

That constrains the hypothesis. LMMH cannot treat oral contraception as a large, uniform switch that predictably delivers a less-masculine partner. If the preference effect exists, it is more likely to be small, heterogeneous, domain-specific (voice, body, dominance, smell, real-world choice rather than lab morphs), or visible mainly when endocrine state changes after a relationship has already formed.

Laboratory facial-preference tasks are one measurement of the phenomenon, not the phenomenon.

Human mate selection integrates multiple sensory and behavioral signals over time. The empirical question is therefore broader than whether a 2013 facial-morph effect replicated in 2019 and 2025: does reproductive endocrine state alter the weighting of masculine characteristics strongly enough, in some women, to influence actual partner selection or later evaluation of the selected partner?

Existing literature does not settle that question. It does settle this much: the preference literature moved. Early positive reports are the opening condition of the model. Later nulls are the ceiling on how far that condition can be pushed as a general law.

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reported preference effect by era: 2013 · 2014 · 2019 · 2025 RCT

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04 Hormonal Congruence and the Man Already Chosen

The most intriguing research may not involve partner selection itself but what happens after the endocrine environment changes.

Longitudinal research on newlywed women reported an interaction between discontinuation of hormonal contraception and husbands' facial attractiveness. Women who had been using hormonal contraception when their relationships formed showed different trajectories of marital satisfaction after discontinuation depending on their husbands' facial attractiveness. 10 (Russell et al., 2014, PNAS 111:17081)

Earlier work generated what became known as the congruency hypothesis: relationship outcomes might depend partly on whether a woman's hormonal-contraceptive state remains congruent with the state under which the partner was originally selected. 11

Recent meta-analysis indicates that the average effect, if present, is small. 9

The conceptual question remains: what happens when a nervous system evaluates an existing mate under a substantially different reproductive endocrine state from the one under which that mate was selected?

Pregnancy and parturition provide an extreme natural experiment in endocrine transition. They are not equivalent to stopping the pill. Contraceptive research should not be projected onto postpartum women. Both literatures raise the broader possibility that mate evaluation is state-dependent.

The useful variable is rapid reproductive endocrine transition, not return to cycling. Pregnancy and parturition do not simply shift a woman "back to endogenous cycling." Postpartum ovulatory cycling can remain suppressed for considerable periods, particularly with lactation. Absolute restoration of a pre-pregnancy cycle is therefore the wrong description of the state change. What matters is the speed and magnitude of the hormonal transition itself.

The relevant structure is therefore not absolute masculinity, and not contraception alone, but an interaction:

female endocrine state at mate selection × female endocrine state after reproductive transition × characteristics of the selected male

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05 Postpartum Psychosis as a Disorder of Transition

Postpartum psychosis is an unusual psychiatric phenotype because of its timing. It often develops rapidly after childbirth, during enormous endocrine, immunological, metabolic, sleep-related, and neurophysiological change. Modern reviews have emphasized its biological character. 3

The simple proposition that falling estrogen or progesterone directly "causes" postpartum psychosis has not been demonstrated. Absolute steroid-hormone concentrations do not reliably distinguish women who become ill from women who remain well. A more sophisticated possibility is differential sensitivity to normal reproductive change. 12

The 2026 international expert consensus on postpartum psychosis emphasizes this broader concept: reproductive hormonal changes can trigger psychiatric symptoms in susceptible individuals, and the postpartum period involves simultaneous profound endocrine and immune transitions. 3 (Bergink et al., 2026, Biological Psychiatry 99:740)

The clinically important phenomenon may not be an abnormal hormone level. It may be an abnormal response to a normal transition.

If attraction, sexual perception, social salience, threat perception, and mate evaluation are partly state-dependent, the male partner should not automatically be treated as a psychologically inert object while her reproductive state changes around him. That change is a rapid endocrine transition after pregnancy and birth, not a tidy return to the ovulatory cycle she had before conception.

He remains biologically the same man. Her perception of him need not remain the same.

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The Less Masculine Man Hypothesis

SECTION 06 · A FOUR-STAGE PATHWAY

Endocrine-dependent mate selection

Little et al. reported that oral-contraceptive initiation decreased preference for masculine male faces and that women using oral contraception when their relationships formed had partners with less-masculine faces. 1 Gori et al. likewise reported lower preference for a broader masculinity composite among pill users. 6 The LMMH takes those findings as its starting condition: when hormonal state reduces the weighting of masculine characteristics during mate selection, the selected partner may occupy a lower position on facial, vocal, physical, or behavioral masculinity dimensions.

Reproductive transition

Subsequent discontinuation of contraception, pregnancy, and parturition produce a rapid reproductive endocrine transition. That transition is not identical to a return to endogenous cycling. Postpartum cycling can remain suppressed for considerable periods, particularly with lactation. The hypothesized state change is the transition itself — the withdrawal and reorganization of pregnancy-level steroids and related systems — not restoration of a pre-pregnancy ovulatory pattern.

Altered relational perception

In a hormonally sensitive subset of women, this state shift recalibrates the social-salience network and changes baseline evaluation of the partner's perceived dominance, physical authority, and sexual dimorphism.

Authority substitution in psychosis

When postpartum psychosis supervenes, that perceptual gap shapes auditory verbal hallucinations. The internal voice system compensates for lower perceived authority in the real-world partner by generating an internal authority representation — a commanding, dominant male voice or entity that commands compliance.

Partner masculinity is therefore proposed as a structural moderator of relational perception, authority, and the phenomenology of command hallucinations.

07 Why the Voice Matters

Auditory verbal hallucinations are perceived as voices despite the absence of a corresponding external speaker. Models of voice hearing have long implicated abnormalities in source monitoring, whereby internally generated verbal material is experienced as though its source were external. 13 Neuroimaging research likewise implicates speech/language systems, auditory cortex, memory systems, and self-representation. 14

Phenomenological externality does not require an external author. The voice remains a product of the nervous system experiencing it, even when consciousness attributes that voice to another person, a supernatural entity, a persecutor, a protector, or an authority.

This becomes particularly interesting with command hallucinations.

Commands are not behaviorally equivalent merely because they are heard. A 2026 systematic review found that compliance is related to perceived power, omnipotence, identity, familiarity, authority, social relationship, emotional force, and consequences attributed to the voice. 15 (Medas & Georgiades, 2026, Clin Psychol Psychother 33:e70246)

The voice exists inside a social hierarchy. It has rank. It possesses — or fails to possess — authority.

That is the bridge between reproductive mate perception and psychotic phenomenology: when endocrine transition changes the salience of masculine or dominance-associated cues, a vulnerable woman's psychotic system generates or amplifies an internal authority representation that supersedes the authority attributed to the actual male partner.

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08 Ritual, Timing, and Opportunity

Command hallucinations should also be studied temporally.

Clinical descriptions usually record what the voice said, how often it occurred, whether the patient believed it, and whether she complied. Less attention is paid to an elementary behavioral question: when does the voice appear?

If a command voice appears when an intimate partner leaves, disappears when he returns, intensifies under isolation, or emerges only after a sequence producing privacy, those temporal relationships are data.

The hypothesis predicts that future research should record partner presence or absence at voice onset, the gender and perceived authority of the voice, whether the voice resembles the partner or contrasts with him, whether commands possess ritualized sequencing, and whether her evaluation of her partner changes alongside voice intensity.

The existing postpartum-psychosis literature has not systematically collected these variables.

09 The Partner Literature Has Measured Almost Everything Except the Partner

This omission becomes striking when the literature on husbands and partners is examined.

Qualitative studies have documented partners' powerlessness, caregiving, loss, coping, barriers to treatment, hypervigilance, changing family roles, and relationship recovery. 4 A 2024 systematic qualitative review synthesized fathers' experiences across the postpartum-psychosis literature. 16 (Lyons et al., 2024, J Adv Nurs 80:413)

Those studies concern what the man does in response to the illness. They do not appear to ask whether the men differ systematically in morphology, voice, dominance, behavioral masculinity, mate value, testosterone-linked traits, or perceived authority.

The central variable proposed here has therefore been absent from existing study design.

The next step is straightforward: measure the man.

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10 Falsifiable Predictions

The hypothesis produces several direct predictions:

Among women with substantial historical exposure to hormonal contraception at relationship formation, male partners should — if earlier findings generalize — score modestly lower on at least some independently measured masculinity dimensions than partners formed during natural cycling.

Partner masculinity alone should not strongly predict postpartum psychopathology. Any association should emerge principally through interaction with reproductive-state transition and individual hormonal sensitivity.

Among women developing postpartum psychosis, partner masculinity should correlate more strongly with symptom content involving authority, dominance, protection, command, or male personification than with unrelated symptoms.

Lower perceived partner dominance or masculinity should, if authority substitution occurs, predict greater authority attributed to a commanding or personified voice.

In cases involving command hallucinations, voice onset and intensity should show measurable relationships to partner presence, absence, conflict, or perceived authority.

If partner masculinity distributions do not differ across relevant groups, and masculinity does not interact with endocrine-state change, hormonal sensitivity, symptom content, or voice authority, the hypothesis receives no support.

11 Study Design: Prospective Cohorts and Dynamic Retrospective Audits

Empirical studies must capture both static morphological structure and dynamic kinematic expression across a spectrum of state expressions.

Option A · Preregistered Multicenter Prospective Cohort

Women enter during preconception or early pregnancy. Investigators record contraceptive history, contraceptive status at relationship formation, psychiatric history, bipolar-spectrum vulnerability, previous postpartum episodes, medication exposure, parity, sleep, trauma history, relationship duration, socioeconomic variables, substance exposure, and relevant medical conditions. Reproductive hormones and neuroactive steroids are sampled longitudinally.

Male partners undergo multimodal assessment:

Option B · Dynamic Retrospective Photo Range Sampling

Where prospective tracking is constrained by rarity, retrospective computer-vision pipelines can extract the same structural-vector metrics without studio environments by sampling individuals across an expressive range (neutral baseline to dynamic affective strain).

By measuring the subject across multiple dynamic states (neutral, smiling [AU 6+12], anger [AU 4+5], disgust [AU 9+10]), computer vision can map how underlying bony landmarks constrain tissue deformation under strain. Range sampling bypasses single-image artifacts and lighting variation and can establish structural vector profiles from archival photographs.

STATE SET := {neutral, AU6+12, AU4+5, AU9+10} VECTOR := f(bony landmark, tissue displacement)

Women developing psychotic symptoms receive detailed phenomenological assessment. For voices, researchers record perceived gender, identity, location, familiarity, benevolence or malevolence, social rank, perceived power, command content, resistance, compliance, timing, and partner presence or absence.

12 Implications for Severe Outcomes

Postpartum psychosis is rare. Its consequences can be catastrophic. Systematic review confirms that delusions and hallucinations can be present in postpartum cases culminating in infanticide. 17 (Alford et al., 2025, Arch Womens Ment Health 28:297)

Rare outcomes may depend on the convergence of several individually modest variables: hormonal sensitivity; psychiatric vulnerability; sleep disruption; reproductive transition; medication changes; relationship dynamics; partner characteristics; voice authority; isolation; opportunity; and individual behavioral response.

A small moderator can matter greatly at the end of a long causal chain.

A weak average effect of hormonal contraception on facial preference would not settle whether endocrine-state-dependent mate perception contributes to a rare psychiatric configuration. The relevant signal may be found in the interaction rather than the population mean.

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13 Limits of the Present Evidence

The model joins several empirical literatures whose endpoints have not yet been connected directly. That creates specific limits:

Present evidence is sufficient to define the question. It is not yet sufficient to answer it.

14 Conclusion

The postpartum-psychosis literature has measured the woman's hormonal state, psychiatric vulnerability, reproductive transition, hallucinations, and relationship distress while leaving one conspicuous variable comparatively untouched: the man she selected before the transition.

Neighboring literatures already provide the components necessary to justify measuring him. Hormonal state has been studied in relation to preferences for masculine characteristics. 1 6 Some research has reported differences in the actual male partners selected under hormonal contraception. 1 Changes in contraceptive state have been associated with changed evaluations of an existing partner. 10 Postpartum psychosis occurs during an extreme reproductive transition in biologically susceptible women. 3 Command hallucinations are structured partly by perceived identity, social rank, power, and authority. 15

The missing empirical question is whether characteristics of the existing male partner interact with those processes.

The Less Masculine Man Hypothesis proposes that the relevant structure is:

hormonal state during mate selection × partner masculinity × subsequent reproductive-state change × psychiatric vulnerability

The first test does not require a new theory of psychosis. It requires measuring a variable that has largely been treated as scenery.

If partner masculinity has no relationship to endocrine transition, mate evaluation, symptom structure, or voice authority, the proposed mechanism disappears. If a relationship emerges, the husband can no longer be treated merely as caregiver, witness, or contextual detail.

Measure the man.

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