Differences in Responding under Fixed-Time and Fixed-Interval Schedules of Electric Shock Presentation

In a squirrel monkey with prior training under a shock-escape schedule, response rate increased and the pattern of positively accelerated responding sharpened when electric shocks (10 mA) were presented on a response-dependent (fixed-interval) rather than on response-independent (fixed-time) basis. The differences in responding under the two schedules were apparent over several transitions from one schedule to the other and were independent of whether or not time-out periods followed presentation of shock. These differences are the same as those seen after similar manipulations of the schedule of presentation of food. The clear differences observed are testament to the degree of control exerted by temporally close and consistent relations between the emission of an operant and presentation of the maintaining event.