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Associations of Serum Androgens and Prenatal Testosterone Biomarkers with Dominance, Aggression, and Strength in Women

This study of 151 young women finds that while serum androgens show generally weak associations with dominance and aggression, the prenatal androgen biomarker anogenital distance (AGD) is a more valuable predictor of these traits than the 2D:4D ratio, suggesting that androgen-behavior links in females are context-dependent and require diverse measurement approaches.

Original authors: Aiden Bushell, Michael Chen, Jun Liu, Bernard Crespi

Published 2026-06-24

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CC BY 4.0

Original authors: Aiden Bushell, Michael Chen, Jun Liu, Bernard Crespi

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine your body as a complex construction site. For a long time, scientists thought the "foreman" of this site for women was mostly Estrogen. But this new study suggests there's another key player, Testosterone, that acts like a subtle but powerful architect, shaping everything from how strong you are to how you act in social situations.

The researchers wanted to see if this "Testosterone Architect" leaves behind blueprints that we can still read today. They looked at two types of blueprints:

The "Current Construction" (Postnatal): How much testosterone is floating in your blood right now.
The "Original Blueprint" (Prenatal): How much testosterone you were exposed to while you were growing in the womb.

To read these blueprints, they used two special measuring tools:

The "Finger Ruler" (2D:4D): The ratio of your index finger to your ring finger. A shorter index finger usually suggests a "bolder" prenatal blueprint.
The "Perineum Tape Measure" (AGD): The distance between your anus and your genitals. A longer distance suggests a "bolder" prenatal blueprint.

Here is what they found, broken down into simple concepts:

1. The "Finger Ruler" vs. The "Tape Measure"

The study compared these two tools to see which one was a better map of the Testosterone Architect's work.

The Result: The Tape Measure (AGD) turned out to be the more reliable map. It showed a clear connection to the actual amount of testosterone currently in the blood.
The Finger Ruler was a bit more confusing. Sometimes it matched the predictions, and sometimes it didn't. It's like trying to guess the weather by looking at a single cloud; sometimes you're right, sometimes you're not. The Tape Measure, however, was like looking at the whole sky.

2. Strength and Social "Bossiness"

The researchers asked: Does having more testosterone (either now or in the womb) make a woman stronger, more aggressive, or more dominant?

The "Muscle" Connection: They found a clear link between Handgrip Strength and a general score of "Dominance/Aggression." Think of it like this: Women who could squeeze harder with their hands also tended to score higher on tests measuring how assertive or dominant they felt. It's as if physical strength and social "pushiness" are two sides of the same coin.
The Hormone Link: The link between actual blood testosterone and these "bossy" traits was weak and shaky. It was like a radio signal that was just barely coming through. While there was a hint that more testosterone might mean more dominance, it wasn't a loud, clear signal. This suggests that for women, the link between hormones and behavior is much more complicated and context-dependent than we previously thought.

3. The "Irregular Clock" (Menstrual Cycles)

The study also looked at women with irregular periods.

The Finding: Women with irregular cycles had significantly higher levels of two specific hormones (Androstenedione and DHEAS).
The Metaphor: Imagine the body's reproductive system as a clock. When the clock is running irregularly, it's often because the "fuel" (these specific hormones) is running a bit too hot. However, this irregularity didn't seem to change their personality, strength, or how dominant they were. It was purely a physiological "fuel" issue.

4. The "Early Bird" Effect (Age of First Period)

They looked at when women started their periods (Menarche).

The Finding: Women who started their periods earlier (around age 11 or younger) tended to score lower on dominance and aggression tests compared to those who started later.
The Metaphor: Think of it as a trade-off. The body might be prioritizing "reproduction mode" (starting early) over "competition mode" (being aggressive or dominant). It's like a car shifting gears: if you shift into "high speed reproduction," you might not have as much power left for "aggressive maneuvering."

The Big Picture Takeaway

This study is like a detective story where the clues were a bit mixed.

The Good News: The Anogenital Distance (AGD) is a fantastic tool for future studies. It's a reliable ruler for measuring prenatal testosterone exposure.
The Reality Check: The idea that "more testosterone = more aggressive/dominant woman" is not a simple straight line. The connection is faint, like a whisper rather than a shout. It seems that in women, behavior is influenced by a mix of hormones, but also by many other invisible factors (like social environment, genetics, and life experiences).

In short: The study confirms that testosterone plays a role in shaping women's bodies and behaviors, but it's not the only director in the room. The "Tape Measure" (AGD) is the best tool we have to see the prenatal blueprint, but the link between hormones and "bossy" behavior is much more subtle and complex than we used to believe.

Technical Summary: Associations of Serum Androgens and Prenatal Testosterone Biomarkers with Dominance, Aggression, and Strength in Women

Problem Statement
Research regarding female hormonal dynamics has historically prioritized estrogen, often overlooking the multifaceted roles of testosterone in female physiology and behavior. While testosterone is known to influence morphology, reproductive function, and behavioral tendencies (such as dominance and aggression) through both immediate ("activational") postnatal effects and long-term ("organizational") prenatal effects, existing findings remain fragmented. Specifically, there is a lack of comprehensive studies that simultaneously evaluate how prenatal and postnatal androgens shape variation across behavioral, physiological, and reproductive domains in women. Furthermore, the reliability of prenatal biomarkers, particularly the comparison between Anogenital Distance (AGD) and the Second-to-Fourth Digit Ratio (2D:4D), requires further validation in the context of female traits. This study addresses these gaps by systematically assessing the associations between serum androgens, prenatal testosterone biomarkers, and a broad spectrum of traits including dominance, aggression, strength, and reproductive health markers.

Methodology
The study utilized a cross-sectional design with a sample of 151 female undergraduate students (mean age = 19) recruited from Simon Fraser University. Participants provided self-measurements and biological samples via a remote protocol:

Physical Measurements: Participants self-measured Anogenital Distance (AGD), Second-to-Fourth Digit Ratio (2D:4D), Handgrip Strength (HGS), Waist-to-Hip Ratio (WHR), and Body Mass Index (BMI) using provided tools (rulers, dynamometers, tapes). AGD and HGS were measured three times to calculate averages.
Hormonal Assays: Participants collected dried blood spots (DBS) for the quantification of serum testosterone, androstenedione (A4), and dehydroepiandrosterone sulfate (DHEAS). Quantification was performed using liquid chromatography–tandem mass spectrometry (LC–MS/MS).
Psychological and Reproductive Questionnaires: Data were collected on social dominance (Simple Adjective Test [SAT], International Personality Item Pool [IPIP]), aggression (Indirect Aggression Scale [IAS-A]), empathy (Empathy Quient Short), and reproductive history (age of menarche, menstrual cycle regularity, contraceptive use).
Statistical Analysis: Analyses were conducted in R. Outliers were removed via visual inspection. Principal Component Analysis (PCA) was used to synthesize dominance and aggression measures into composite scores (PC1 for overall dominance/aggression; PC2 for indirect vs. direct dominance). Correlations, t-tests, and ANOVAs were employed to test associations between hormonal/biomarker variables and the outcome measures.

Key Contributions

Comparative Validation of Biomarkers: The study directly compares AGD and 2D:4D as biomarkers of prenatal androgen exposure within the same female cohort, providing empirical data on their concordance and reliability.
Integrative Approach: Unlike prior studies that often examine behavioral, morphological, and reproductive traits in isolation, this research integrates these domains to evaluate the holistic impact of androgens on female phenotype.
Differentiation of Androgen Types: The study distinguishes between postnatal circulating androgens (testosterone, A4, DHEAS) and prenatal exposure markers, testing their specific associations with distinct trait clusters.
Nuanced Behavioral Analysis: By utilizing PCA to separate overall dominance/aggression (PC1) from the dimension of indirect versus direct aggression (PC2), the study offers a more granular view of how androgens relate to specific behavioral strategies.

Results

Biomarker Correlations: Serum testosterone, A4, and DHEAS were strongly positively correlated with each other. AGD showed a significant positive correlation with serum testosterone ( $r = .29$ ) and WHR ( $r = .23$ ), and a negative correlation with right-hand 2D:4D ( $r = -.20$ ). In contrast, serum androgens and 2D:4D showed no significant associations with BMI, WHR, or HGS.
Dominance and Aggression:
- PC1 (Overall Dominance/Aggression): Scores were positively correlated with Handgrip Strength ( $r = .26$ ) and marginally associated with serum testosterone ( $r = .25, p = .055$ ).
- PC2 (Indirect vs. Direct): PC2 scores were negatively associated with AGD ( $r = -.24$ ), suggesting lower prenatal androgen exposure in females with higher indirect relative to direct aggression. Conversely, PC2 was negatively associated with 2D:4D (both hands), suggesting higher prenatal exposure for this specific behavioral profile.
- Specific Measures: AGD was positively correlated with SAT scores (social dominance), whereas left-hand 2D:4D was positively correlated with SAT scores, a finding that contrasts with the typical hypothesis that lower 2D:4D indicates higher dominance.
Reproductive Health:
- Menstrual Irregularity: Females with irregular menstrual cycles exhibited significantly higher levels of A4 and DHEAS compared to those with regular cycles. No significant differences were found for testosterone, AGD, 2D:4D, or physical traits.
- Age of Menarche (AOM): AOM was negatively correlated with BMI. Participants with the earliest menarche ( $\le$ 11 years) showed significantly lower PC1 and SAT scores compared to older groups.
Empathy: WHR was negatively correlated with empathy (EQ), while EQ was positively correlated with SAT scores.

Significance and Claims
The paper claims that its findings advance the understanding of how androgens influence female behavior and reproductive health, while maintaining a modest stance on the strength of these associations.

AGD Utility: The results highlight AGD as a potentially more valuable and consistent measure than 2D:4D for studying androgen-related traits in women, given its stronger associations with serum androgens and specific dominance traits.
Context-Dependency: The study indicates that androgen-behavior associations in females may be weaker or more context-dependent than previously thought. The largely null associations between many androgen-behavior pairs suggest that these traits are likely shaped by a complex interplay of factors beyond simple hormonal levels, including psychosocial, genetic, and epigenetic influences.
Methodological Importance: The authors emphasize the necessity of using multiple measures of both androgens (serum and biomarkers) and dominance (direct vs. indirect) to capture the full spectrum of these relationships.
Clinical Relevance: The findings contribute to the broader understanding of conditions involving androgen dysregulation, such as Polycystic Ovary Syndrome (PCOS), by linking specific hormonal profiles (e.g., elevated A4/DHEAS in irregular cycles) to reproductive outcomes.

The authors conclude that while prenatal and postnatal androgens do contribute to female dominance and aggression, the effects are variable and likely mediated by trade-offs between reproductive timing, survival, and competitive behaviors.