While human neuroimaging studies typically collapse data from many subjects, brain functional organization varies between individuals, and characterizing this variability is crucial for relating brain activity to behavioral phenotypes. Rest, in which subjects lie quietly in the scanner with no explicit task, has become the default state for probing individual differences, chiefly because it is easy to acquire and a supposed neutral backdrop. However, the assumption that rest is the optimal condition for individual differences research is largely untested. In fact, certain tasks may afford a better ratio of within- to between-subject variability, facilitating biomarker discovery. Using a large sample of healthy individuals from the Human Connectome project, I will show that individual differences in functional brain connectivity do, in fact, depend on the condition in which they are measured. I will also show preliminary results from a novel naturalistic task paradigm specifically designed to elicit a range of interpretations across individuals, thus drawing out variation in both brain networks and behaviors of interest. One ultimate goal of this line of work is to develop neuropsychiatric “stress tests” to enhance individual differences in the general population, or, in at-risk individuals, to reveal abnormal patterns of brain activity before they show up at rest.