The second study, by Schneider et al. (2), looked at two other often correlated traits—risk taking and substance abuse. It is known that addictive behaviors are linked to reduced activation of the ventral striatum, the “reward system” of the brain. However, it is not known whether risk-seeking behaviors, separate from addiction, are also associated with changes in the brain's reward system, which may explain their common co-occurrence. Schneider et al. chose to investigate this question by studying a community sample of young teens, among whom many may have higher levels of risk-seeking behaviors, but not yet addictive behaviors. Their sample consisted of 266 healthy 14-year-olds, with an additional subset of 31 teens with substance use. Risk-taking bias was assessed prior to MRI scanning, by the Cambridge Gamble Task. During functional MRI, reward anticipation was stimulated by a modified version of the monetary incentive delay task. The structural MRI analysis focused on determining the total gray matter volume for each subject, normalizing the scans, and then comparing them voxel by voxel to determine whether risk taking is correlated with structural variability in gray matter. The statistical models controlled for gender (given gender differences in risk taking), pubertal status, handedness, an intelligence estimate, and scanning site.