Skip to main content
  • Submit
  • About
    • Editorial Board
    • PNAS Staff
    • FAQ
    • Accessibility Statement
    • Rights and Permissions
    • Site Map
  • Contact
  • Journal Club
  • Subscribe
    • Subscription Rates
    • Subscriptions FAQ
    • Open Access
    • Recommend PNAS to Your Librarian
  • Log in
  • My Cart

Main menu

  • Home
  • Articles
    • Current
    • Special Feature Articles - Most Recent
    • Special Features
    • Colloquia
    • Collected Articles
    • PNAS Classics
    • List of Issues
  • Front Matter
  • News
    • For the Press
    • This Week In PNAS
    • PNAS in the News
  • Podcasts
  • Authors
    • Information for Authors
    • Editorial and Journal Policies
    • Submission Procedures
    • Fees and Licenses
  • Submit
  • About
    • Editorial Board
    • PNAS Staff
    • FAQ
    • Accessibility Statement
    • Rights and Permissions
    • Site Map
  • Contact
  • Journal Club
  • Subscribe
    • Subscription Rates
    • Subscriptions FAQ
    • Open Access
    • Recommend PNAS to Your Librarian

User menu

  • Log in
  • My Cart

Search

  • Advanced search
Home
Home

Advanced Search

  • Home
  • Articles
    • Current
    • Special Feature Articles - Most Recent
    • Special Features
    • Colloquia
    • Collected Articles
    • PNAS Classics
    • List of Issues
  • Front Matter
  • News
    • For the Press
    • This Week In PNAS
    • PNAS in the News
  • Podcasts
  • Authors
    • Information for Authors
    • Editorial and Journal Policies
    • Submission Procedures
    • Fees and Licenses

New Research In

Physical Sciences

Featured Portals

  • Physics
  • Chemistry
  • Sustainability Science

Articles by Topic

  • Applied Mathematics
  • Applied Physical Sciences
  • Astronomy
  • Computer Sciences
  • Earth, Atmospheric, and Planetary Sciences
  • Engineering
  • Environmental Sciences
  • Mathematics
  • Statistics

Social Sciences

Featured Portals

  • Anthropology
  • Sustainability Science

Articles by Topic

  • Economic Sciences
  • Environmental Sciences
  • Political Sciences
  • Psychological and Cognitive Sciences
  • Social Sciences

Biological Sciences

Featured Portals

  • Sustainability Science

Articles by Topic

  • Agricultural Sciences
  • Anthropology
  • Applied Biological Sciences
  • Biochemistry
  • Biophysics and Computational Biology
  • Cell Biology
  • Developmental Biology
  • Ecology
  • Environmental Sciences
  • Evolution
  • Genetics
  • Immunology and Inflammation
  • Medical Sciences
  • Microbiology
  • Neuroscience
  • Pharmacology
  • Physiology
  • Plant Biology
  • Population Biology
  • Psychological and Cognitive Sciences
  • Sustainability Science
  • Systems Biology
Letter

Joel et al.'s method systematically fails to detect large, consistent sex differences

Marco Del Giudice, Richard A. Lippa, David A. Puts, Drew H. Bailey, J. Michael Bailey, and David P. Schmitt
PNAS April 5, 2016 113 (14) E1965; first published March 16, 2016; https://doi.org/10.1073/pnas.1525534113
Marco Del Giudice
aDepartment of Psychology, University of New Mexico, Albuquerque, NM 87131;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • For correspondence: marcodg@unm.edu
Richard A. Lippa
bDepartment of Psychology, California State University, Fullerton, CA 92831;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
David A. Puts
cDepartment of Anthropology, Center for Behavior, Brain, and Cognition, and Center for Human Evolution and Diversity, Pennsylvania State University, State College, PA 16801;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Drew H. Bailey
dSchool of Education, University of California, Irvine, CA 92697;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
J. Michael Bailey
eDepartment of Psychology, Northwestern University, Evanston, IL 60208;
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
David P. Schmitt
fDepartment of Psychology, Bradley University, Peoria, IL 61625
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site

This Letter has a Reply and related content. Please see:

  • Reply to Del Giudice et al., Chekroud et al., and Rosenblatt: Do brains of females and males belong to two distinct populations? - March 16, 2016
  • Sex beyond the genitalia: The human brain mosaic - November 30, 2015

See related content:

  • Male and female brains are distinct
    - Mar 16, 2016
  • Predictable human brain mosaic
    - Mar 16, 2016
  • Article
  • Info & Metrics
  • PDF
Loading

In their widely publicized paper, Joel et al. (1) make two empirical claims about sex differences in features of the human brain: (i) “…internal consistency [in individuals’ sex-differentiated brain features] is rare” (p. 15472) and (ii) the amount of overlap in sex-differentiated features of male and female brains “undermines any attempt to distinguish between a ‘male’ and a ‘female’ form for specific brain features” (p. 15471). We argue that claim i is based on faulty methodology, and claim ii is misleading if extended to overall sex differences in brain structure.

In regard to claim ii, Joel et al. (1) did not conduct analyses (e.g., discriminant analyses) designed to test how well various brain features predicted participants’ sex. Performing such analyses on the data of Joel et al. (1), we found that brain features correctly predicted subjects’ sex about 69–77% of the time (2). Moreover, the multivariate overlap of female and male distributions based on the same variables was moderate (42% on average), and certainly not so large as to invalidate the idea of overall sex differences in brain structure.

As for claim i, the definition of “internal consistency” Joel et al. (1) use is so extreme that, in realistic conditions, it can only generate results consistent with their hypothesis. Via simulations, we systematically varied sample characteristics such as the magnitude of sex differences and correlations among variables. Some of the simulated scenarios were intentionally unrealistic, involving uniformly strong sexual dimorphism and/or extremely high correlations between variables (up to r = 0.90). Despite this, the proportion of “internally consistent” profiles remained low in all conditions. Under more realistic assumptions, the method of Joel et al. (1) virtually always returned the same pattern of results—a preponderance of “substantially variable” profiles, a minority of “intermediate profiles,” and a very small proportion (often close to zero) of “sex-typical” profiles (2).

These results are supported by Joel et al.’s own analysis of sex-typed activities (figure 2 in ref. 1, p. 15471; data from ref. 3). Taken together, activities showed a clear bimodal distribution with almost no overlap between the sexes. However, even here, Joel et al. (1) report that “55% of subjects showed substantial variability and only 1.2% were internally consistent.” In short, there seems to be no degree of sexual dimorphism in realistic datasets that will yield results that falsify the hypotheses of Joel et al. (1).

To further reinforce this point, we applied Joel et al.’s methods to facial morphology features in three species of monkeys (crab-eating macaques, grivets, and tufted capuchins). Our goal was to see what percent of individual monkeys would display internally consistent species-typical profiles of features (2). Across comparisons, only 1.1–5.1% of the monkeys showed consistent “species-typical” profiles, whereas 18.9–25.3% had “intermediate” profiles (as expected based on the extremely large size of species differences, there were no “substantially variable” profiles). If the methods of Joel et al. (1) cannot demonstrate consistency in morphological features that distinguish distinct species, is it any wonder that they cannot demonstrate within-individual consistency in sexually differentiated brain structures and behaviors in humans?

Footnotes

  • ↵1To whom correspondence should be addressed. Email: marcodg{at}unm.edu.
  • Author contributions: M.D.G., R.A.L., D.A.P., D.H.B., J.M.B., and D.P.S. designed research; M.D.G. and D.H.B. analyzed data; and M.D.G., R.A.L., D.A.P., D.H.B., J.M.B., and D.P.S. wrote the paper.

  • The authors declare no conflict of interest.

View Abstract

References

  1. ↵
    1. Joel D, et al.
    (2015) Sex beyond the genitalia: The human brain mosaic. Proc Natl Acad Sci USA 112(50):15468–15473
    .
    OpenUrlAbstract/FREE Full Text
  2. ↵
    1. Del Giudice M, et al.
    (2015) Mosaic brains? A methodological critique of Joel et al. (2015). Available at cogprints.org/10046/
    .
  3. ↵
    1. Carothers BJ,
    2. Reis HT
    (2013) Men and women are from Earth: Examining the latent structure of gender. J Pers Soc Psychol 104(2):385–407
    .
    OpenUrlCrossRefPubMed
PreviousNext
Back to top
Article Alerts
Email Article

Thank you for your interest in spreading the word on PNAS.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
Joel et al.'s method systematically fails to detect large, consistent sex differences
(Your Name) has sent you a message from PNAS
(Your Name) thought you would like to see the PNAS web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
Method fails to detect sex differences
Marco Del Giudice, Richard A. Lippa, David A. Puts, Drew H. Bailey, J. Michael Bailey, David P. Schmitt
Proceedings of the National Academy of Sciences Apr 2016, 113 (14) E1965; DOI: 10.1073/pnas.1525534113

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Request Permissions
Share
Method fails to detect sex differences
Marco Del Giudice, Richard A. Lippa, David A. Puts, Drew H. Bailey, J. Michael Bailey, David P. Schmitt
Proceedings of the National Academy of Sciences Apr 2016, 113 (14) E1965; DOI: 10.1073/pnas.1525534113
Digg logo Reddit logo Twitter logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Mendeley logo Mendeley
Proceedings of the National Academy of Sciences: 113 (14)
Table of Contents

Submit

Sign up for Article Alerts

Article Classifications

  • Biological Sciences
  • Neuroscience

Jump to section

  • Article
    • Footnotes
    • References
  • Info & Metrics
  • PDF

You May Also be Interested in

Abstract depiction of a guitar and musical note
Science & Culture: At the nexus of music and medicine, some see disease treatments
Although the evidence is still limited, a growing body of research suggests music may have beneficial effects for diseases such as Parkinson’s.
Image credit: Shutterstock/agsandrew.
Scientist looking at an electronic tablet
Opinion: Standardizing gene product nomenclature—a call to action
Biomedical communities and journals need to standardize nomenclature of gene products to enhance accuracy in scientific and public communication.
Image credit: Shutterstock/greenbutterfly.
One red and one yellow modeled protein structures
Journal Club: Study reveals evolutionary origins of fold-switching protein
Shapeshifting designs could have wide-ranging pharmaceutical and biomedical applications in coming years.
Image credit: Acacia Dishman/Medical College of Wisconsin.
White and blue bird
Hazards of ozone pollution to birds
Amanda Rodewald, Ivan Rudik, and Catherine Kling talk about the hazards of ozone pollution to birds.
Listen
Past PodcastsSubscribe
Goats standing in a pin
Transplantation of sperm-producing stem cells
CRISPR-Cas9 gene editing can improve the effectiveness of spermatogonial stem cell transplantation in mice and livestock, a study finds.
Image credit: Jon M. Oatley.

Similar Articles

Site Logo
Powered by HighWire
  • Submit Manuscript
  • Twitter
  • Facebook
  • RSS Feeds
  • Email Alerts

Articles

  • Current Issue
  • Latest Articles
  • Archive

PNAS Portals

  • Anthropology
  • Chemistry
  • Classics
  • Front Matter
  • Physics
  • Sustainability Science
  • Teaching Resources

Information

  • Authors
  • Editorial Board
  • Reviewers
  • Librarians
  • Press
  • Site Map
  • PNAS Updates

Feedback    Privacy/Legal

Copyright © 2021 National Academy of Sciences. Online ISSN 1091-6490