Evidence map›Paper›PMID 39500803›Full record

ArticleArchives of sexual behavior2025

Ejaculate Adjustment in Response to Sperm Competition Risk in Humans.

Tara DeLecce, Gavin S Vance, Virgil Zeigler-Hill, Lisa L M Welling, Todd K Shackelford

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Article in Archives of sexual behavior, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.

0numbers the graph read from it
0cells of the map it votes in
2citing papers in PubMed
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

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Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

2 citing papers in PubMed.

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4 · The record

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PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

5 authors.

Tara DeLecceDepartment of Psychology, Oakland University, 213B Pryale Hall, Rochester, MI, 48309, USA. tdelecce@oakland.edu.ORCID 0000-0002-4611-6952
Gavin S VanceDepartment of Psychology, Oakland University, 213B Pryale Hall, Rochester, MI, 48309, USA.
Virgil Zeigler-HillDepartment of Psychology, Oakland University, 213B Pryale Hall, Rochester, MI, 48309, USA.
Lisa L M WellingDepartment of Psychology, Oakland University, 213B Pryale Hall, Rochester, MI, 48309, USA.
Todd K ShackelfordDepartment of Psychology, Oakland University, 213B Pryale Hall, Rochester, MI, 48309, USA.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

Previous research suggests that human males, like males of many mammalian and avian species, adjust their ejaculate quality in accordance with sperm competition risk. Men who spend less time with their regular female partner since the couple's last copulation produce ejaculates with more sperm at the couple's next copulation (Baker & Bellis, 1993). We conducted a conceptual replication of this research to investigate whether sperm competition risk predicts ejaculate adjustment in human males using additional measures of sperm competition risk (e.g., perceptions of partner infidelity, presence of potential sexual rivals) and updated laser-optic semen analysis technology. We collected data from 34 heterosexual couples (age range 18-32 years) from a university population who completed self-report surveys on their relationship dynamics and provided six ejaculate samples (three copulatory and three masturbatory) across a 45-day period. Time spent together since the couple's last copulation was not significantly associated with ejaculate quality. However, sperm concentration for copulatory ejaculates was higher for men who perceived more potential sexual rivals. Discussion situates the current results within the literature on human sperm competition and suggests several directions for future research.

Indexed as

EjaculationSexual BehaviorSpermatozoaAdolescentAdultCopulationFemaleHumansMaleSemen AnalysisSexual PartnersSperm CountYoung AdultEjaculate adjustmentEjaculate qualityEvolutionary psychologyHuman sperm competition

Identifiers

PMID39500803

What OpenQuestion holds

Textmetadata
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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.