Assessment & Research

Are Autistic Traits in the General Population Related to Global and Regional Brain Differences?

Koolschijn et al. (2015) · Journal of autism and developmental disorders 2015
★ The Verdict

In neurotypical adults, autistic personality traits do not show up as brain-structure differences.

✓ Read this if BCBAs who use trait questionnaires with college-age or adult clients.
✗ Skip if Clinicians working only with diagnosed ASD who already have brain imaging data.

01Research in Context

01

What this study did

Kocher et al. (2015) asked a simple question. Do people with more autistic-like traits also have different-looking brains?

They scanned 508 college students. All were neurotypical. Each filled out the Autism-Spectrum Quotient.

MRI measured gray-matter volume and white-matter integrity across the whole brain. Stats looked for trait-brain links.

02

What they found

The answer was no. Higher AQ scores did not predict bigger or smaller brain areas.

White-matter tracts also looked the same, regardless of trait level.

In plain words: personality quirks alone do not show up on these brain pictures.

03

How this fits with other research

Kunihira et al. (2006) got the ball rolling. They showed that AQ scores in non-autistic adults link to mood and personality traits. Kocher et al. (2015) used the same tool but added brain scans—and found nothing. Together, the studies draw a line: traits can shape behavior without leaving a structural footprint.

Low et al. (2024) looked at Malaysian students who self-reported high traits. Those students felt more stress and lower quality of life. Kocher et al. (2015) found no brain differences, yet Low et al. (2024) found real-life struggles. The pair warns us: visible suffering does not require visible brain change.

Kuenssberg et al. (2011) struggled to fit clinical autism symptoms into tidy boxes. Kocher et al. (2015) shows the mess extends downward: even mild, sub-clinical traits do not map cleanly onto brain structure. Both papers chip away at the idea that autism—clinical or not—is a simple neural gradient.

04

Why it matters

For BCBAs, this means trait questionnaires tell you about client experience, not brain anatomy. Use AQ or similar tools to guide conversation and support, not to predict neurology. When a neurotypical client reports social difficulty, focus on skill building and mental-health care instead of hunting for hidden brain deficits.

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Treat high trait scores as behavioral targets, not neural verdicts—teach social skills or coping strategies right away.

02At a glance

Intervention
not applicable
Design
other
Sample size
508
Population
neurotypical
Finding
null

03Original abstract

There is accumulating evidence that autistic-related traits in the general population lie on a continuum, with autism spectrum disorders representing the extreme end of this distribution. Here, we tested the hypothesis of a possible relationship between autistic traits and brain morphometry in the general population. Participants completed the short autism-spectrum quotient-questionnaire (AQ); T1-anatomical and DWI-scans were acquired. Associations between autistic traits and gray matter, and white matter microstructural-integrity were performed on the exploration-group (N = 204; 105 males, M-age = 22.85), and validated in the validation-group (N = 304; 155 males, M-age = 22.82). No significant associations were found between AQ-scores and brain morphometry in the exploration-group, or after pooling the data. This questions the assumption that autistic traits and their morphological associations do lie on a continuum in the general population.

Journal of autism and developmental disorders, 2015 · doi:10.1371/journal.pone.0049172