Aversive Events as Positive Reinforcers: An Investigation of Avoidance and Safety Signals in Humans

Introduction It is well established that stimuli correlated with the absence of aversive events may come to signal periods of safety from those events. In previous research, stimuli that signaled periods of safety were largely neutral in nature. In the present investigation, we examined whether aversive events also could be conditioned as safety signals. Methods Seven university students were initially exposed to a 72 dB tone, which all rated as highly aversive. Next, they were required to play a computerized game in which mouse clicks on a map produced points (treasures) or point losses (bombs). Participants were instructed that bombs could be disabled by pressing a foot pedal, although pedal presses pro- duced the aversive tone. In the next phase of the game, no bombs were programmed. During some sessions, pedal presses produced the tone and in other sessions they did not. Results Rates of pedal pressing maintained when the sound was produced; however, pedal pressing eventually ceased in sessions in which it was absent. Follow-up measures indicated that 6 of the 7 participants rated the tone as aversive at the end of the study. Discussion These findings suggest that the aversive stimulus functioned as a positive reinforcer, given that participants chose to produce the sound even when it did not abate aversive stimulation.