Reproductive regulation: motivation, capacity and care

How a shared biological state can produce coordinated—and selectively different—behavioural outcomes.

Reproduction is regulated before a pregnancy begins. Biological state shapes what attracts attention, whether an approach occurs, how another individual responds and which physiological transitions can succeed. The same system also regulates care. BERM connects these three branches to explain both shared changes and the outputs that remain intact.

Three branches from a shared receiving state

The physical input enters BERM through its conditional receiving response, then the existing calcium, redox, clock, metabolic and hormone-receptor states. The experiments here identify downstream biological and social transitions. They give the model a concrete structure for reproductive regulation; the geometric input and its tissue-specific calibration remain the separate upstream link.

Receiving state + hormonal timing + learned history + present context

Motivation and realisation

Desire and cue response → approach → another individual’s response → a realised encounter or attempt.

Measure desire, action and opportunity separately.

Peragine et al. (2017)iMills et al. (2023)i

Physiological capacity

GnRH/LH responsiveness → gonadal function and reserve → the biological success of an encounter.

Measure current hormone levels, stimulated response and functional success separately.

Abbott et al. (1988)iHoskova et al. (2022)i

Realised encounters and conditional biological success → reproductive timing and births

Caregiving and feedback

Sensitivity to caregiving cues → directed care → changed contact and learning → later responses.

Measure the amount and target of care alongside reproductive activity.

Clarkson et al. (2026)iWeisman et al. (2012)i

Care → later contact, learning and receiving state

Realisation includes pregnancy-exposing encounters as well as intentional attempts, so unplanned pregnancies remain in the pathway. External resources, timing and constraints contribute to opportunity. Care and subsequent social contact form their own feedback branch, rather than a compulsory step before every birth.

A reproductive brake can be selective

A biological intervention can reduce reproductive-axis activation and sexually directed behaviour while several other functions remain available.

In naked mole-rats, RFRP-3 administration after colony removal prevented a progesterone rise and reduced opposite-sex genital investigation. Other social investigation, movement and several additional responses remained intact. The experiment locates a selective output pattern: a general loss of activity is unnecessary to explain the reproductive change. Peragine 2017 i.

Marmoset removal and return experiments place social context upstream of LH and ovulation. Together with the hormone-challenge literature, they identify reproductive-axis responsiveness more precisely than a universal high-cortisol state. For BERM, selectivity adds explanatory power: a shared receiving state can change particular target circuits while preserving other functions. Abbott 1988 i.

One hormonal signal, different target circuits

Reproductive-axis activation and caregiving can diverge because the same hormonal system acts through distinct receiving pathways.

Prolactin → kisspeptin → reproductive-axis response

In mice, prolactin exposure reduced kisspeptin expression and reproductive-axis activity; kisspeptin restored ovarian cycling. In women with hyperprolactinaemia, repeated kisspeptin administration increased LH pulses without a significant overall reduction in prolactin. The human endpoint was a pulse response.

Sonigo et al. (2012)iHoskova et al. (2022)i

Prolactin-sensitive MPOA–VTA → offspring contact

A separate mouse study located a prolactin-sensitive circuit supporting offspring contact and a related dopamine response. Activating the pathway increased contact even in females that had not given birth. Circuit-specific intervention identifies a caregiving route.

Clarkson et al. (2026)i

BERM synthesis: the shared hormone connects these experiments at a named biological variable. Different receptors, circuits and reproductive phases explain why care can be maintained or strengthened while reproductive-axis activation falls. Kohl’s projection-specific work and Ammari’s pregnancy-related circuit plasticity further separate components and timescales of care. Kohl 2018 i; Ammari 2023 i.

The amount of care and its target are different outcomes. Own-child care, care for another child and care for an animal require their own contact histories and measures. A caregiving relationship becomes informative about reproductive regulation when it is joined to the same person’s physiological and behavioural sequence.

The order of change helps locate the gate

Social behaviour, hormone pulses, gonadal reserve and a birth occupy different clocks. Follow each measured variable through time instead of assigning one recovery time to the whole profile.

Behaviour can change before slow tissue remodelling
Social opportunity in cichlids produced rapid behavioural and local gene-expression responses; related work measured gonadotropin changes within 30 minutes. These are different measurements in the same research programme, with their own experimental samples.
Burmeister et al. (2005)iMaruska et al. (2011)i
Behaviour can also outlast measured hormone differences
A visual social cue maintained subordinate behaviour across seven days while measured physiological differences were transient or absent by the final time point. The visible behaviour therefore did not identify the entire current physiological state.
Chen et al. (2011)i
Reserve can remain available during social suppression
Suppressed male cichlids retained spermatogenesis and could fertilise within hours of a social opportunity. A suppressed reproductive role and complete loss of biological capacity are distinct states.
Kustan et al. (2012)i
Realised reproductive transitions are followed across longer intervals
Cebu analyses connect fatherhood, testosterone and sexual activity within one cohort. Friendship and workplace studies add the timing of later reproductive transitions. Their longer follow-up supplies a different measurement scale from an acute hormone challenge.
Gettler et al. (2013)iBalbo et al. (2014)iPink et al. (2014)i

Read the evidence as a matrix of measured transitions

Compare the intervention, biological measurement, observed output and time course. The research family stays attached when several papers describe the same cohort or experimental programme.

Reproductive branchEvidence kindResearch family

31 studies · 20 research families

Families identify shared cohorts and research lineages; these counts do not assume independent replication.

Component experiments manipulate a biological or social input. An experiment in a wild animal group retains that classification: the measured intervention determines its place in the chain.

Bell et al. (2014)Component experimentWild meerkats; 12 groupsKalahari meerkat studies

Input or comparison

Contraception versus saline in a crossover design

Measured change and output

Suppressing subordinate reproduction increased pup feeding and reduced dominant aggression and eviction.

Biological and contextual measurements

Pregnancy
Social status, eviction or aggression

Observed outcomes

Observed caregiving
Availability of reproductive interactions

Time course

Two nine-month periods, 2009–2011; 59 dominant reproductive attempts

Shared data and research lineage

Shared research system; contraception and eviction studies are different designs.

Scope of the finding

Group opportunities and pregnancy costs also changed; the experiment does not isolate intrinsic caregiving motivation.

Source and corrections

Bell et al. (2014)i

Young et al. (2006)Observational studySubordinate female meerkatsKalahari meerkat studies

Input or comparison

Natural eviction followed longitudinally; GnRH challenge

Measured change and output

Eviction coincided with higher glucocorticoids, reduced pituitary response and poorer reproductive outcomes.

Biological and contextual measurements

Cortisol or glucocorticoid metabolites
Response to a GnRH challenge
Social status, eviction or aggression

Observed outcomes

Pregnancy
LH and its pulse pattern

Time course

Eviction and return around dominant pregnancy

Shared data and research lineage

Shared research system; contraception and eviction studies are different designs.

Scope of the finding

Eviction was not randomized and cortisol mediation was not isolated by receptor blockade.

Source and corrections

Young et al. (2006)i

Abbott et al. (1981)Component experimentFemale common marmosets; ten peer groupsMarmoset neuroendocrinology

Input or comparison

LH-RH, estrogen and TRH challenges

Measured change and output

Subordinates had anovulation and reduced LH-RH responsiveness without high cortisol or hyperprolactinemia.

Biological and contextual measurements

Response to a GnRH challenge
Cortisol or glucocorticoid metabolites
Prolactin

Observed outcomes

LH and its pulse pattern
Ovulation or ovarian cycle

Time course

Established social groups and acute hormone challenges

Shared data and research lineage

Related research programme; repeated challenges and animals must not be counted as independent replications.

Scope of the finding

A reproductive-axis brake is not equivalent to a universal elevated-stress-hormone state.

Source and corrections

Abbott et al. (1981)i

Abbott et al. (1988)Component experimentFive subordinate female marmosets in the relocation sequenceMarmoset neuroendocrinology

Input or comparison

Removal from subordination and reintroduction to subordinate groups

Measured change and output

Removal raised LH and estrogens before ovulation; renewed subordination lowered LH and stopped ovulation.

Biological and contextual measurements

Social status, eviction or aggression
LH and its pulse pattern
Estradiol

Observed outcomes

Ovulation or ovarian cycle
Response to a GnRH challenge

Time course

LH returned to low levels within four days of renewed subordination

Shared data and research lineage

Related research programme; repeated challenges and animals must not be counted as independent replications.

Scope of the finding

Four days describes the LH fall after renewed subordination, not a universal fertility-loss time.

Source and corrections

Abbott et al. (1988)i

Saltzman et al. (2004)Component experimentMarmoset families: 11 replacement and seven control familiesMarmoset neuroendocrinology

Input or comparison

Replace father with an unrelated male; remove and return father in controls

Measured change and output

Most daughters mated with the unfamiliar male; daughters conceived in 8/11 families, while ovulation reflected mother–daughter dominance.

Biological and contextual measurements

Social status, eviction or aggression
Partnered sexual activity
Ovulation or ovarian cycle

Observed outcomes

Pregnancy
Availability of reproductive interactions

Time course

Family reorganization and subsequent reproduction

Shared data and research lineage

Related research programme; repeated challenges and animals must not be counted as independent replications.

Scope of the finding

Partner-directed behavior and ovarian readiness are linked but distinct gates.

Source and corrections

Saltzman et al. (2004)i

Burmeister et al. (2005)Component experimentAstatotilapia burtoni males; small genomic comparisonCichlid social plasticity

Input or comparison

Removal of the suppressing male before lights on

Measured change and output

Dominant behavior changed within 14 minutes and Egr-1 increased in the GnRH1-rich preoptic area.

Biological and contextual measurements

Gene expression
Social status, eviction or aggression

Observed outcomes

Sexually directed interest
Circuit activity or neural response

Time course

Minutes after social opportunity

Shared data and research lineage

Shared species and research programme; some hormonal assays reuse the same social-ascent animals.

Scope of the finding

The gene comparison used four ascending, three subordinate and three dominant fish; Egr-1 necessity was not tested.

Source and corrections

Burmeister et al. (2005)i

Follow the same person and the same biological variable

The strongest next connection often exists inside published data. Cebu’s fatherhood and sexual-activity analyses join hormones and behaviour within a shared cohort. NSSHB distinguishes solitary and partnered sexual outputs; PSID follows sexual activity alongside relationships and life-course conditions. These analyses begin to recover a joint profile from outcomes otherwise studied separately.

Gettler et al. (2011)iGettler et al. (2013)iHerbenick et al. (2022)iLei et al. (2020)i

Within one experiment

Which biological variables and behaviours changed after the defined intervention? Which measured outputs were preserved?

Within one cohort

How do physiology, desire, contact and reproductive transitions align in the same people and observation windows?

Across studies

Which named intermediate joins the studies, and which transition is supplied by BERM’s synthesis?

Five observations with different roles

Desire: What feels wanted or attractive now.
Expectation: What the person considers likely under current conditions.
Intention: What action is planned, and on what timescale.
Attempt or encounter: What actually occurs between people, including exposure without an intention to conceive.
Pregnancy or birth: A later event with its own biological conditions and timing.

Biological state can change both an individual’s approach and the responses of others; BERM carries these contributions into opportunity and realised encounters while retaining external constraints.

Eight axes, measured at different points in the sequence

The existing comparison axes become more informative when their measurements are joined within the same study or cohort. The table locates each axis as an input, receiving state, action or later outcome.

Comparison axis	Joint measurement	What existing evidence connects
Care allocation	Caregiving target and time × reproductive state × contact response	Prolactin-sensitive offspring contact and father–infant interaction locate different caregiving transitions. Clarkson 2026 i; Weisman 2012 i.
Dispersal and social proximity	Contact seeking × others’ response × realised contact × household transition	Sleep loss altered social distance and observer responses. PSID analyses connect sexual activity with relationships and living conditions in the same young adults. Ben Simon 2018 i; Lei & South 2021 i.
Stress and reproductive responsiveness	HPA dynamics alongside GnRH/LH response and ovulation	Marmoset status transitions locate LH and ovulation changes. Reproductive-axis responsiveness supplies a more specific measurement than inferring the same cortisol direction for every suppression pathway. Abbott 1988 i.
Courtship and sexual motivation	Desire × partner-directed approach × sexual response × realised encounter	RFRP-3 changed sexually directed investigation selectively. Kisspeptin changed measured human sexual responses. These are distinct components of initiation and realisation. Peragine 2017 i; Mills 2023 i.
Signal production and reception	Specified sensory cue × receiver state × measured response	Queen odour supplies a defined chemical input in naked mole-rats; human infant-odour experiments measure reward-related responses. The shared level is the cue–receiver–response relationship. Khallaf 2026 i; Lundström 2013 i.
Social regulation	Sanction or support × contact availability × later action	Human network studies identify timed reproductive transitions after peer births. Together with interpersonal interventions, they constrain how others’ actions become a new opportunity structure. Balbo & Barban 2014 i; Pink 2014 i.
Hormonal and genomic change	Hormone and pulse timing × receptor response × fatherhood × sexual activity	The Cebu fatherhood and sexual-activity analyses share a cohort. Kisspeptin challenge under hyperprolactinaemia identifies a separate human pulse-response transition. Gettler 2011 i; Gettler 2013 i; Hoskova 2022 i.
Risk, exploration and effort	Reward and effort choices × developmental stage × resources × later action	Dopamine and sleep interventions identify effort-related choices; PSID adds realised activities and life-course conditions. The observed task and the later demographic transition remain separately measured. Westbrook 2020 i; Jurgelis 2022 i; Lei & South 2021 i.

The strongest shared profile comes from several outcomes measured in the same individuals, followed through time. A household category, a caregiving target or a reported preference alone does not identify the receiving state. The eight axes organise these observations into a common causal question.

Three feedbacks connect the individual to population change

A change in behaviour becomes part of another individual’s sensory and social input. Repeated contact, reproduction and institutions can carry the change across different timescales.

Contact feedback

The person’s state changes their actions and how others respond. This changes the next set of available contacts, cues and learning experiences. Sleep-loss and father–infant interventions locate direct interpersonal transitions.

Ben et al. (2018)iWeisman et al. (2012)i

Reproduction and caregiving feedback

Births change access to infants and care. Contact changes later responsiveness and activity. Prolactin’s different targets show why stronger caregiving need not mean greater activation toward a new pregnancy.

Clarkson et al. (2026)iGettler et al. (2013)i

Practice and institutional feedback

Repeated actions and reported reasons change shared practices, schedules, services and options encountered by later cohorts. Fertility-network observations locate timed social transmission; the broader institutional continuation is BERM synthesis.

Balbo et al. (2014)iPink et al. (2014)i

A loop that strengthens the initial change is reinforcing feedback. Its persistence depends on the signs, strength and delays of the links. BERM already distinguishes physiological recovery, learning, social networks and institutional memory, so a population trajectory can persist after one acute biological measure has recovered.

The integrated conclusions and their sources

BERM synthesis across studies

Selective reproductive regulation

Reproductive activation, sexual interest and retained physiological reserve are coordinated but separable outputs of biological regulation.

Scope of the connection: Protocol-specific component directions support the structure; they do not identify a common field dose or universal suppression score.

Abbott et al. (1981)iAbbott et al. (1988)iBurmeister et al. (2005)iMaruska et al. (2011)iChen et al. (2011)iKustan et al. (2012)iPeragine et al. (2017)iKhallaf et al. (2026)iHart et al. (2024)iEdwards et al. (2025)iSonigo et al. (2012)iHoskova et al. (2022)iFinkelstein et al. (2013)iMills et al. (2023)iThurston et al. (2022)i

BERM synthesis across studies

Caregiving and reproductive allocation

A shared hormonal state can engage different receptor and circuit targets, preserving or increasing care while another reproductive output is restrained.

Scope of the connection: PRL suppression and PRL-receptive care circuits are separate component experiments; pet ownership and childlessness are not suppression diagnoses.

Bell et al. (2014)iWatarai et al. (2018)iSonigo et al. (2012)iHoskova et al. (2022)iClarkson et al. (2026)iKohl et al. (2018)iAmmari et al. (2023)iGettler et al. (2011)iWeisman et al. (2012)iNagasawa et al. (2015)i

BERM synthesis across studies

From motivation to realized encounters

Biologically formed motivation and others’ responses help determine realized encounters and conception attempts, separately from the capacity to conceive.

Scope of the connection: Human joint-output and interaction data support the intermediate structure; the complete hormonal-to-birth route is a composition.

Saltzman et al. (2004)iGettler et al. (2013)iHerbenick et al. (2022)iLei et al. (2020)iBen et al. (2018)i

BERM synthesis across studies

Social feedback and population timing

Individual states change social cues and network opportunities; responses of other biological agents feed back into later reproductive timing.

Scope of the connection: Network associations provide timing constraints, not measured endocrine mediation or a calibrated civilization feedback coefficient.

Bell et al. (2014)iYoung et al. (2006)iAbbott et al. (1988)iWeisman et al. (2012)iBen et al. (2018)iBalbo et al. (2014)iPink et al. (2014)i

Existing data that can join the measurements

The resources below retain their population, time window, access conditions and measured variables. Published analyses and available data support the structural integration without assigning unobserved hormone or field values to individuals.

Wild meerkats; 12 groupsKalahari meerkat studies

Contraception versus saline in a crossover design

Collection years: 2009–2011

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Group opportunities and pregnancy costs also changed; the experiment does not isolate intrinsic caregiving motivation.

Open the documented resource iBell et al. (2014)i

Subordinate female meerkatsKalahari meerkat studies

Natural eviction followed longitudinally; GnRH challenge

Publication year: 2006

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Eviction was not randomized and cortisol mediation was not isolated by receptor blockade.

Open the documented resource iYoung et al. (2006)i

Female common marmosets; ten peer groupsMarmoset neuroendocrinology

LH-RH, estrogen and TRH challenges

Publication year: 1981

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A reproductive-axis brake is not equivalent to a universal elevated-stress-hormone state.

Open the documented resource iAbbott et al. (1981)i

Five subordinate female marmosets in the relocation sequenceMarmoset neuroendocrinology

Removal from subordination and reintroduction to subordinate groups

Publication year: 1988

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Four days describes the LH fall after renewed subordination, not a universal fertility-loss time.

Open the documented resource iAbbott et al. (1988)i

Marmoset families: 11 replacement and seven control familiesMarmoset neuroendocrinology

Replace father with an unrelated male; remove and return father in controls

Publication year: 2004

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Partner-directed behavior and ovarian readiness are linked but distinct gates.

Open the documented resource iSaltzman et al. (2004)i

Astatotilapia burtoni males; small genomic comparisonCichlid social plasticity

Removal of the suppressing male before lights on

Publication year: 2005

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The gene comparison used four ascending, three subordinate and three dominant fish; Egr-1 necessity was not tested.

Open the documented resource iBurmeister et al. (2005)i

Astatotilapia burtoni social ascentCichlid social plasticity

Social ascent with time-resolved endocrine measurements

Publication year: 2011

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Later 6–120-hour trajectories differ by endpoint; associated 11-ketotestosterone data reuse previously published animals.

Open the documented resource iMaruska et al. (2011)i

60 Astatotilapia burtoni males across three time pointsCichlid social plasticity

Larger male visible across a watertight transparent barrier

Publication year: 2011

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Visible behavior does not identify the full physiological state; testis-size differences were not significant.

Open the documented resource iChen et al. (2011)i

Socially suppressed Astatotilapia burtoni malesCichlid social plasticity

Release from social suppression and fertility testing

Publication year: 2012

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Suppressed reproductive activity did not mean loss of all gonadal reserve.

Open the documented resource iKustan et al. (2012)i

Naked mole-rats, Heterocephalus glaberMole-rat peptide and release studies

Central RFRP-3 infusion after removal from the colony

Publication year: 2017

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Testosterone differences were not significant; sufficiency of the administered peptide is not proof of endogenous necessity.

Open the documented resource iPeragine et al. (2017)i

Female naked mole-rat helpersMole-rat caregiving cues

Pregnant queen feces or estrogen-supplemented fecal material

Publication year: 2018

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The endpoint was pup-cue responsiveness, not total caregiving or a demonstration that infertility automatically creates care.

Open the documented resource iWatarai et al. (2018)i

Naked mole-rat pairs and queenless colonyMole-rat odour and endocrine studies

Queen-enriched isopropyl myristate, colony bedding and withdrawal

Publication year: 2026

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A chemical cue experiment is not EMF dose equivalence; the colony withdrawal is not a multi-colony replication.

Open the documented resource iKhallaf et al. (2026)i

24 female naked mole-rats from 12 coloniesMole-rat odour and endocrine studies

GnRH challenges, ovariectomy, handling and naloxone

Publication year: 2024

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Repeated assays share animals; some smaller-worker comparisons reuse earlier Faulkes data.

Open the documented resource iHart et al. (2024)i

Naked mole-rat pairs after colony removalMole-rat peptide and release studies

Removal, pairing and longitudinal reproductive follow-up

Publication year: 2025

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The 26-pair analysis includes the eight focal pairs plus 18 earlier Toor pairs. Nonbreeding within a year is not permanent damage.

Open the documented resource iEdwards et al. (2025)i

Naked mole-rat pairs after colony removalMole-rat peptide and release studies

Removal, pairing and longitudinal reproductive follow-up

Publication year: 2025

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The 26-pair analysis includes the eight focal pairs plus 18 earlier Toor pairs. Nonbreeding within a year is not permanent damage.

Open the documented resource iEdwards et al. (2025)i

Hyperprolactinemic female miceProlactin–kisspeptin mouse studies

Chronic prolactin exposure and kisspeptin rescue

Publication year: 2012

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A localized endocrine rescue; not a human caregiving or environmental-field experiment.

Open the documented resource iSonigo et al. (2012)i

11 women with hyperprolactinemiaHuman hyperprolactinemia studies

Two 12-hour visits; repeated kisspeptin on the second visit

Publication year: 2022

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Use corrected version of record; the study did not demonstrate ovulation, pregnancy or caregiving change.

Open the documented resource iHoskova et al. (2022)i

Prolactin-receptive mouse MPOA–VTA circuitProlactin-receptive caregiving circuits

Circuit activation and removal of prolactin action

Publication year: 2026

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The caregiving circuit and endocrine suppression studies are separate experiments joined by a shared hormone.

Open the documented resource iClarkson et al. (2026)i

Mouse MPOA galanin neurons and projectionsParental circuit architecture

Projection-specific optogenetic interventions

Publication year: 2018

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A structured caregiving programme is not one undifferentiated motivation variable.

Open the documented resource iKohl et al. (2018)i

Pregnant and nonpregnant female miceParental circuit architecture

Pregnancy-hormone and parental-circuit manipulation

Publication year: 2023

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Circuit history adds persistence to acute hormonal regulation; not evidence of permanent suppression.

Open the documented resource iAmmari et al. (2023)i

400 healthy men aged 20–50 in two cohortsGonadal steroid suppression and replacement

Gonadal suppression, randomized testosterone doses and aromatase inhibition

Publication year: 2013

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A causal hormone-to-function anchor, without calibrated environmental-field transfer.

Open the documented resource iFinkelstein et al. (2013)i

37 randomized men with HSDD; 32 completed both visitsKisspeptin and sexual processing

Blinded kisspeptin versus placebo crossover

Collection years: 2021

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Distinct neural, physiological and subjective endpoints; no measured child-desire or conception-attempt outcome.

Open the documented resource iMills et al. (2023)i

40 randomized women with HSDD; 32 completed both visitsKisspeptin and sexual processing

Kisspeptin–placebo crossover in the early follicular phase

Collection years: 2020–2021

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: A neural response is not proof of a broad clinical desire or fertility improvement.

Open the documented resource iThurston et al. (2022)i

Cebu fatherhood and testosterone follow-upCebu fatherhood cohort

Shared 2005 and 2009 male cohort measurements

Collection years: 2005, 2009

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The 624-person fatherhood report and 433-person sex report overlap; biomarkers are not assumed unrestricted.

Open the documented resource ↗Gettler et al. (2011)i

35 father–infant dyads; infants about five months oldFather–infant hormonal interaction

Paternal intranasal oxytocin–placebo crossover

Publication year: 2012

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Dyadic transfer is measured; later papers reuse this cohort rather than providing independent replication.

Open the documented resource iWeisman et al. (2012)i

NSSHB ages 14–49; 4,155 in 2009 and 4,547 in 2018National Survey of Sexual Health and Behavior

Repeated cross-sections and latent classes of sexual behavior

Collection years: 2009

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Question-specific denominators differ; adult 72.7% versus 72.5% solo activity was not a significant change.

Open the documented resource iHerbenick et al. (2022)i

NSSHB ages 14–49; 4,155 in 2009 and 4,547 in 2018National Survey of Sexual Health and Behavior

Repeated cross-sections and latent classes of sexual behavior

Collection years: 2018

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Question-specific denominators differ; adult 72.7% versus 72.5% solo activity was not a significant change.

Open the documented resource iHerbenick et al. (2022)i

3,213 US adults aged 18–23; fixed-effect subset 655PSID transition to adulthood

Longitudinal PSID-TAS mediation and within-person analysis

Collection years: 2007–2017

Individual observationsLongitudinal design

Access: Public data are free after registration; participant identifiers link waves.

Measurement scope: Measured mediation is not demonstrated hormonal mediation or environmental-field attribution.

Open the documented resource ↗University et al. (2026)i

Human sleep-loss experiment and independent video observersSleep and social interaction

Sleep deprivation and social-distance judgments

Publication year: 2018

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: The interaction-opportunity bridge is measured; mate formation and reproduction are a further conditional continuation.

Open the documented resource ↗Ben et al. (2018)i

Dogs, human caregivers and hand-raised wolvesHuman–dog affiliative feedback

Mutual gaze observation and canine oxytocin–placebo intervention

Publication year: 2015

Individual observationsOther observation design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: No child-desire, human infertility or replacement-parenthood endpoint; urinary oxytocin is not a direct brain concentration.

Open the documented resource iNagasawa et al. (2015)i

Add Health friendship and parenthood recordsAdd Health friendship networks

Longitudinal observational network analysis

Publication year: 2014

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Selection and shared context require modelling; no hormonal mediator was measured.

Open the documented resource iBalbo et al. (2014)i

33,119 women in 6,579 German firmsGerman workplace fertility records

Linked employer–employee fertility histories

Collection years: 1993–2007

Individual observationsLongitudinal design

Access: Published methods and results are available; unrestricted participant-level access is not asserted.

Measurement scope: Observational workplace propagation; not a neural or hormonal intervention.

Open the documented resource iPink et al. (2014)i

NHANES hormones and behaviorNHANES examination surveys

Join TST_H, SXQ_H, RHQ_H, SLQ_H and DEMO_H by SEQN.

Collection years: 2013–2014

Individual observationsOther observation design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: Use common age/assay eligibility and weights; assay conversion is needed for some cross-cycle testosterone comparisons.

Open the documented resource ↗CDC/NCHS et al. (2016)i

NSHAP biomarkers and social lifeNSHAP aging and social life

Repeated salivary sex hormones, sexual interest and social-network measurements.

Collection years: 2005–2006; 2010–2011

Individual observationsLongitudinal design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: Wave 1 includes over 3,000 adults aged 57–85; public and restricted files differ.

Open the documented resource ↗ICPSR/NACDA et al. (2026)i

NSFG intentions, activity and family historyNational Survey of Family Growth

9,957 respondents: 5,586 women and 4,371 men aged 15–49.

Collection years: 2022–2023

Individual observationsOther observation design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: Use both survey years and weights; historical comparisons often restrict to 15–44. No measured hormones.

Open the documented resource ↗CDC/NCHS et al. (2025)i

GSS behavior and attitudesGeneral Social Survey

Sexual activity, family and selected attitudes in shared questionnaire records.

Collection years: 1972–2024

Individual observationsOther observation design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: Verify form overlap and the changed 2024 PARTNERS coding; cumulative cross-sections are not a single-person panel.

Open the documented resource ↗NORC et al. (2026)i

MTF youth behavior profilesMonitoring the Future

6,895 grade-12 respondents with six randomized forms and a common core.

Collection years: 2024

Individual observationsOther observation design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: All variables are not measured in every respondent; school surveys and the separate adult panel differ.

Open the documented resource ↗University et al. (2025)i

Pew child expectations and social contextPew American Trends Panel

Reported reasons, pressure, social ties and caregiving among selected adults without children.

Collection years: 2024-04-29–2024-05-19

Individual observationsOther observation design

Access: Official documentation and access route; account or restricted-data terms may apply.

Measurement scope: The 57% reason statistic concerns 18–49-year-olds already expecting no future children, with multiple reasons permitted.

Open the documented resource ↗Pew et al. (2024)i

Download the evidence catalogue

Three branches from a shared receiving state

Motivation and realisation

Physiological capacity

Caregiving and feedback

A reproductive brake can be selective

One hormonal signal, different target circuits

Prolactin → kisspeptin → reproductive-axis response

Prolactin-sensitive MPOA–VTA → offspring contact

The order of change helps locate the gate

Behaviour can change before slow tissue remodelling

Behaviour can also outlast measured hormone differences

Reserve can remain available during social suppression

Realised reproductive transitions are followed across longer intervals

Read the evidence as a matrix of measured transitions

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Input or comparison

Measured change and output

Biological and contextual measurements

Observed outcomes

Time course

Shared data and research lineage

Scope of the finding

Source and corrections

Follow the same person and the same biological variable

Within one experiment

Within one cohort

Across studies

Five observations with different roles

Eight axes, measured at different points in the sequence

Three feedbacks connect the individual to population change

Contact feedback

Reproduction and caregiving feedback

Practice and institutional feedback

The integrated conclusions and their sources

Selective reproductive regulation

Caregiving and reproductive allocation

From motivation to realized encounters

Social feedback and population timing

Existing data that can join the measurements