Breast Size as a Geographically Differentiated Indicator of Intelligence: Why Breast Size Preference Differs

Breast Size as a Geographically Differentiated Indicator of Intelligence: Why Breast Size Preference Differs

Author: Cloudfindings

Date: April 23, 2025

Cite as: Cloudfindings (2025) Breast Size as a Geographically Differentiated Indicator of Intelligence: Why Breast Size Preference Differs. Cloudfindings. Cloudfindings.io/papers/breastsize.pdf

Large breasts have been considered to be often seen as more attractive than smaller breasts to men, however, this preference is not universal, and a significant portion of men prefer smaller breasts (Swami & Tovee 2013). Research on breast size preference as well as the correlates of breast size has been very limited, and differences in breast size preference have not been sufficiently explained. In this paper, I put forth a promising hypothesis explaining breast size preference with multiple lines of evidence, and outline predictions of this hypothesis.

Evidence for Breast Size Relationship With Intelligence

Within the very limited research on this topic, Swami & Tovee (2013) found that wealth predicted a preference for smaller breasts. While many plausible explanations exist for this, one possible explanation is that more intelligent men prefer smaller breasts, as socioeconomic status correlates highly with intelligence (Crespi 2016). With this hypothesis, I propose that the reason for this preference is one of assortative mating, and that breast size itself is an indicator of intelligence in women. Coming to mind initially is the relationship between ethnicity and intelligence and ethnicity and breast size - across racial groups, average IQ correlates inversely with average breast size (Rushton 2013). Preference for large breasts has been thought to reflect that larger breasts can indicate more access to resources through fat (Swami & Tovee 2013), however signaling resources through fat is not universally attractive and the preference for body fat varies throughout the world (Gray & Frederick 2012). Eating disorders relate to increased mating effort and enhancement of physical attractiveness by reducing body weight, and the prevalence of eating disorders by ethnicity correlates positively with intelligence and negatively with breast size (Van Dyne et al. 2023). Anorexia is associated with higher intelligence (Lopez et al. 2010), and obesity is associated with low intelligence (Yu et al. 2010). 

IQ differences between races relate largely to geography and how it affects the environment for natural selection, and varies more over specific regions than races (Lynn 2003). There is some evidence that resource scarcity, particularly in environments with water scarcity selects for lower cognitive abilities but colder environments select for higher cognitive abilities (de Baca et al. 2014). This is in line with race differences in intelligence, with races from environments with warm and dry environments having lower IQs and larger secondary sexual characteristics on average, and races from colder and water rich environments having higher IQs and smaller secondary sexual characteristics (Lynn 2003). In environments that are low in water scarcity (enabling agriculture, reduced time spent traveling, etc) but have cold temperatures, perhaps intelligence becomes selected over indications of access to resources, as these environments would select for building systems that allow for growing food during the warmer seasons, but having to protect from a cold climate -  making use of the environment to create better living conditions, such as agriculture, shelter, systems for moving water, without having to change geographical location would mean that selection for traits in women would no longer reflect resource scarcity, but rather their intelligence and things like femininity, being skinny being an indicator of feminization to a degree (Cloudfindings & Younas 2024) and thinness is preferred in female body shapes (Akande 1993). There would also be concern of overconsumption of resources in these environments, leading to obesity which is detrimental to fertility (Dag et al. 2015), and also is also an indicator of several diseases, some that directly impact fertility in women (Weaver 2008). Larger breasts also indicate old age (Coltman et al 2018), and selection against old age would be more prevalent in races with slower life history strategies (as slower life history strategies involve longer lifespan), and breast size & life history speed correlate positively across ethnicity (Rushton 2013) - races and regions with higher IQs also having slower life history speeds (Rushton 2013)(de Baca et al. 2014). This would mean larger breasts would be selected against now, because women with larger breasts would more likely be obese and therefore have disease or infertility, or old age which also is a major indicator of infertility - women in their early 20s being the most fertile, declining in late 20s steadily through 30s and on average women becoming infertile at 45 (Garcia et al. 2018). Small breast size would then indicate that a) the woman does not overconsume, therefore would not be subject to the problems with reproduction and health associated with obesity; b) the woman does not have various common genetic diseases that cause obesity c) that the woman has high enough intelligence (Lopez e tal. 2010) and especially social intelligence (Warrier et al. 2018) to be able to maintain their own body weight to be healthy and attractive to men d) the woman would give more food resources to the offspring, and men are selected for genes that favor offsprings health over mothers health (Crespi 2008) meaning if the woman was so skinny that she had slightly reduced fertility, it may still be selected for because it would indicate the mother would be more suitable for raising a mans offspring by not consuming a large portion of available food and instead giving it to her offspring  - though being too skinny reduces attractiveness, which likely reflects the disease and infertility associated with being too underweight (Akande 1993), often being complications of severe eating disorders e) the woman is younger and therefore more fertile, as women in their early 20s are most fertile, and decline thereafter, and sharply decline toward their 40s, where breast size increases. 

Breast Size & IQ Across Countries

To provide evidence for this hypothesis, I gathered data on breast size across countries (Worlddata 2025) and IQ across countries (Lynn & Becker 2019). Bra size was coded the following: AAA = 0; AA = 1; A = 2; A-B = 3; B = 4; B-C = 5; C = 6; C-D = 7. A polynomial regression was performed on countries that had data for both bra size and IQ, and a 6 order polynomial regression was found to have the best fit (though, a 3 and 4 order regression found the same result, in case of overfitting - a 4 order regression seemed to be the best fitting), explaining 44% of the variance in breast size, a 4 order regression explain 40% of the variance. All regressions found that IQ positively correlated with IQ up until the point of 100, at which there was a sharp turn in the direction of the correlation, IQ having a strong negative correlation with countries with an average IQ above 100. Displayed is the 4 order polynomial regression, as it appeared to fir the data best, with lower orders underfitting and higher orders overfitting [Figure 1]. In countries which IQ was above 100, data was obtained from Average Height (2024) due to lack of data from Worlddata, and the correlation with IQ and average bra size was found to be r=-0.73, explaining 52% of the variance in bra size in higher IQ countries, this correlation was statistically significant (p=0.016) [Figure 2]. This data, while not on an individual level, strongly supports the hypothesis presented in this paper.

Figure 1

Figure 2

Conclusion

Overall, the evidence points to breast size preference being largely determined by ancestry - individuals thats ancestry is rooted in regions with high resource scarcity that don’t allow for the development of higher intelligence and more complex systems such as agriculture are likely to prefer larger breasts, but individuals that have ancestry in regions with lower resource scarcity that allow for the development of higher intelligence and slower life history strategies due to being able to develop more complex systems of gaining resources such as agriculture are likely to prefer small breasts. This explains the weak evidence of small breast size preference being associated with intelligence (Swami et al. 2013). Slower life history strategies which on a geographical level are positively correlated with intelligence (Rushton 2013)(de Baca et al. 2014) also predict preference for smaller breasts, and variation in preference for breast size across different regions of the world has been well demonstrated (Havlíček et al. 2017). One prediction of this hypothesis is that breast size should have an inverse assortative mating correlation with intelligence, in such that more intelligent men tend to mate with smaller breasted women. 

1. Swami, V., & Tovée, M. J. (2013). Resource security impacts men’s female breast size preferences. PLoS One, 8(3), e57623.

2. Crespi, B. J. (2016). Autism as a disorder of high intelligence. Frontiers in neuroscience, 10, 300.

3. Rushton, J. P. (2013). Ethnic differences in temperament. In Personality and person perception across cultures (pp. 45-63). Psychology Press.

4. Van Dyne, A., Washington, N., Villodas, M., & Cronan, T. (2023). Racial/ethnic differences in anorexia and bulimia diagnoses among US college students. Eating Behaviors, 50, 101779.

5. Gray, P. B., & Frederick, D. A. (2012). Body image and body type preferences in St. Kitts, Caribbean: A cross-cultural comparison with US samples regarding attitudes towards muscularity, body fat, and breast size. Evolutionary Psychology, 10(3), 631-655.

6. Lopez, C., Stahl, D., & Tchanturia, K. (2010). Estimated intelligence quotient in anorexia nervosa: a systematic review and meta-analysis of the literature. Annals of General Psychiatry, 9, 1-10.

7. Yu, Z. B., Han, S. P., Cao, X. G., & Guo, X. R. (2010). Intelligence in relation to obesity: a systematic review and meta‐analysis. Obesity Reviews, 11(9), 656-670.

8. Lynn, R. (2003). The geography of intelligence. In The scientific study of general intelligence (pp. 127-146). Pergamon.

9. de Baca, T. C., & Figueredo, A. J. (2014). The cognitive ecology of Mexico: Climatic and socio-cultural effects on life history strategies and cognitive abilities. Intelligence, 47, 63-71.

10. Cloudfindings & Younas (2024) Explaining Paraphilia: A Novel Model Explaining A Wide Range of Sexual Interests Continuous With Normal Sexuality. Cloudfindings. cloudfindings.io/papers/paraphilia.pdf

11. Akande, A. (1993). Sex differences in preferences for ideal female body shape. Health care for women international, 14(3), 249-259.

12. Dağ ZÖ, Dilbaz B. Impact of obesity on infertility in women. J Turk Ger Gynecol Assoc. 2015 Jun 1;16(2):111-7. doi: 10.5152/jtgga.2015.15232. PMID: 26097395; PMCID: PMC4456969.

13. Weaver, J. (2008). Classical endocrine diseases causing obesity. Frontiers of hormone research, 36, 212.

14. Warrier, V., Toro, R., Chakrabarti, B., iPSYCH-Broad Autism Group, Børglum, A. D., Grove, J., ... & Baron-Cohen, S. (2018). Genome-wide analyses of self-reported empathy: correlations with autism, schizophrenia, and anorexia nervosa. Translational psychiatry, 8(1), 35.

15. Crespi, B. (2008). Genomic imprinting in the development and evolution of psychotic spectrum conditions. Biological Reviews, 83(4), 441-493.

16. Coltman, C. E., Steele, J. R., & McGhee, D. E. (2018). Effects of age and body mass index on breast characteristics: a cluster analysis. Ergonomics, 61(9), 1232-1245.

17. García, D., Brazal, S., Rodríguez, A., Prat, A., & Vassena, R. (2018). Knowledge of age-related fertility decline in women: A systematic review. European Journal of Obstetrics & Gynecology and Reproductive Biology, 230, 109-118.

18. Havlíček, J., Třebický, V., Valentova, J. V., Kleisner, K., Akoko, R. M., Fialová, J., ... & Roberts, S. C. (2017). Men's preferences for women's breast size and shape in four cultures. Evolution and Human Behavior, 38(2), 217-226.

19. Worlddata (2025) Average breast size worldwide. Worlddata. https://www.worlddata.info/average-breastsize.php

20. Lynn, R., & Becker, D. (2019). The intelligence of nations. London, UK: Ulster Institute for Social Research.

21. Average Height (2024) The World's Average Bra Cup Size: A Country-by-Country Breakdown. Average Height. https://www.averageheight.co/averages/human-body-metrics/average-breast-cup-size/