Responding under a Constant-Probability Schedule of Electric Shock Presentation

In squirrel monkeys responding under a continuous avoidance schedule, addition of a 3-min. constant-probability variable-interval schedule of response-produced shock (concurrent avoidance 3-min. VI) increased responding. When the avoidance schedule was eliminated, so that the only consequence of responding was the presentation of response-dependent shock under the VI schedule, characteristic VI patterns of responding were maintained. In other monkeys already responding under a 3-min. VI schedule without the constant-probability feature, characteristic patterns of responding were also maintained under the constant-probability schedule. Schedule-appropriate performances are maintained under VI schedules of shock presentation in which there is little relation between probability that a given response will be shocked and the time that has passed since the last shock, i.e., a constant-probability schedule. Substantial shock-free periods just after shock are not necessary for responding to be engendered and maintained under schedules of shock presentation.