Delay of Shock-Escape with and without Stimulus Change

Effects of a stimulus change presented with delay of shock-escape were examined in escape conditioning. Where a stimulus change occurred with the delay, greater response rates were found before delay and lower rates during the delay. Results are interpreted as providing evidence for the efficacy of a stimulus change in maintaining behavior with delay of negative reinforcement. Results are consistent with an information account of secondary reinforcement. Data from a control procedure suggest the possibility that stimuli paired with shock termination might have two opposite properties, secondary reinforcing and conditioced aversive, depending upon the background stimulus conditions prevailing at testing.