Distractibility in daily life is reflected in the structure and function of human parietal cortex.

We all appreciate that some of our friends and colleagues are more distractible than others. This variability can be captured by pencil and paper questionnaires in which individuals report such cognitive failures in their everyday life. Surprisingly, these self-report measures have high heritability, leading to the hypothesis that distractibility might have a basis in brain structure. In a large sample of healthy adults, we demonstrated that a simple self-report measure of everyday distractibility accurately predicted gray matter volume in a remarkably focal region of left superior parietal cortex. This region must play a causal role in reducing distractibility, because we found that disrupting its function with transcranial magnetic stimulation increased susceptibility to distraction. Finally, we showed that the self-report measure of distractibility reliably predicted our laboratory-based measure of attentional capture. Our findings distinguish a critical mechanism in the human brain causally involved in avoiding distractibility, which, importantly, bridges self-report judgments of cognitive failures in everyday life and a commonly used laboratory measure of distractibility to the structure of the human brain.