The scientists raised mice lacking normal gut microflora, then compared their behavior, brain chemistry and brain development to mice having normal gut bacteria.

FORBES: Thinking With Your Gut. Literally.

Parracho HM, Bingham MO, Gibson GR, McCartney AL. Differences between the gut microflora of children with autistic spectrum disorders and that of healthy children.

FORBES: Anti-Vaccine Activists Apparently Immune To Science