The purpose of the current experiment was to investigate the role of private verbal behavior on the operant performances of human adults, using a protocol analysis procedure with additional methodological controls (the "silent dog" method). Twelve subjects were exposed to fixed ratio 8 and differential reinforcement of low rate 3-s schedules. For 6 subjects, verbal self-reports were recorded concurrently during exposure to the reinforcement schedules. Results showed a significant relationship between certain types of rules and task performances, and especially between counting and schedule-sensitive performance. A detailed analysis also suggested that counting facilitated the discrimination of programmed contingencies in the current task. Suggestions are offered for further research involving the use of the protocol analysis methodology.