Although routinely used, control group criteria vary considerably in research. Drawing from aspects in our normative study on musical emotion perception, we show how a group of participants who would normally be considered a control group in most studies, display clear event-related potential (ERP) differences when grouped by affective assessment scores that are rarely administered to presumed “control” group candidates. This preliminary finding demonstrates the importance of careful screening of control group membership. Failure in this process can produce misleading observations, undermining the validity of results.