The scientists raised mice lacking normal gut microflora, then compared their behavior, brain chemistry and brain development to mice having normal gut bacteria.
Parracho HM, Bingham MO, Gibson GR, McCartney AL. Differences between the gut microflora of children with autistic spectrum disorders and that of healthy children.
When they add nothing, as lambic-makers do, the untreated wort becomes a refuge for airborne wild microflora, which now have space to grow and food that would otherwise be hogged by beer yeast to eat.