Behavioral Contrast In Pigeon Depends Upon The Location Of The Stimulus

Three pigeons were exposed to a series of multiple schedules of reinforcement-both multiple variable interval extinction, and multiple variable interval variable interval. The stimuli which signaled the two components of the multiple schedule were sometimes located on the response key, and sometimes removed from the key. Positive behavioral contrast (increases in variable-interval responding which accompany decreases in extinction responding) was only observed when the signal stimuli were on the response key. These findings are consistent with the view that positive contrast results from the introduction of a differential stimulus-reinforcer dependency which directs behavior toward the stimulus, as in the phenomenon of autoshaping