The promise of neurophenotyping psychiatric symptoms implies a need for methods that yield reliable and valid measures of brain activity in individual patients. Balodis and Potenza (1) have provided a comprehensive and nuanced review of the use of the monetary incentive delay (MID) task to probe symptoms related to addiction. In this commentary, we briefly reflect on the history of the MID task, situate these findings within the broader context of other disorders, and speculate about implications for research and practice. The first author (BK) developed the MID task during the latter half of the 1990s as a postdoctoral fellow in Hommer’s intramural laboratory at the National Institute on Alcohol Abuse and Alcoholism. Inspired by success of researchers using functional magnetic resonance imaging to map neural correlates of sensory and motor function, the MID task was designed to leverage the spatial and temporal resolution of functional magnetic resonance imaging (i.e., millimeters and seconds) to “localize” affective responses deep in the brain. Because individuals varied in their affective responses to other incentives (e.g., images, sounds, tastes), money was adopted as an incentive that could influence affect more consistently. Money also provided a convenient experimental stimulus because it could be 1) either gained or lost (i.e., assigned positive or negative valence), 2) cued as well as delivered (i.e., distinguishing responses to anticipation vs. outcomes), and 3) cued with different attributes (e.g., signifying valence, magnitude, probability, uncertainty, delay, effort). Incorporating both gain and loss conditions allowed researchers to control for potential confounds related to sensory stimulation, arousal, salience, and motor preparation. Researchers could also stabilize dynamic expectations within subjects after brief training (including learning) and control performance across subjects with adaptively timed targets, facilitating assessment of reliable affective and neural responses to incentives (2). Initial findings indicated that experientially, MID task gain cues elicited “positive aroused” affect, whereas loss cues elicited “negative aroused” affect—suggesting that incentive anticipation and outcomes could powerfully induce affect. Neurally, gain cues proportionally increased activity in the nucleus accumbens (NAcc) of the ventral striatum, whereas both loss and gain cues proportionally increased activity in the anterior insula and medial caudate. Even within cues, individual differences in NAcc activity correlated with positive arousal. The MID task became a popular “localizer” for eliciting NAcc activity during reward anticipation (2). activity of the NAcc during anticipation of large gains (e.g., 1$5.00) versus nongains (e.g., 1$0.00) typically shows large effect sizes (e.g., f 5 3.07), implying that significant results can be obtained in small samples (e.g., six subjects at a power of .80) (3).