This study investigated the effects of two levels of social and material reinforcement on the verbal performance of 104 university males who were divided into Impulsive and Nonimpulsivc groups by paper-and-pcncil tests. A Taffel-type verbal conditioning task was used. Following preliminary instructions given to ,9s in person, all further interaction took place with R in an adjoining control room. Social reinforcement involved prerecorded comments : "mm-hm" or "ok" for weak; "good," "that's good," "very good," "excellent," or "fine" for strong. The material reinforcement was either 2(' (weak) or 15<# (strong). Thus the design was a 2X2X2 factorial for type of reinforcement, intensity, and level of impulsivity. Only data from aware .?s were included in the analysis. Material reinforcement was found to be more effective than social reinforcement for all blocks of reinforced trials (/><.01). There were no significant effects for intensity or impulsivity. Results were discussed in terms of awareness of the response-reinforcement contingency and differential valuation of incentives.