THE EFFECT OF TIMEOUT ON PERFORMANCE ON A VARIABLE‐INTERVAL SCHEDULE OF ELECTRIC‐SHOCK PRESENTATION¹

Abstract

Responding was maintained in squirrel monkeys under variable-interval schedules of electric shock presentation when a period of timeout followed each response-dependent shock. Response rate decreased when timeout duration was decreased, and responding ceased wheni timeout was eliminated. These results in(licate that under certain conditions, a shock-free period following each response-produced shock is necessary to maintain responding.Recent studies have demonstrated that animals with specific types of behavioral hiistories will continue to respond when the only consequence of responding is the occasional presentation of a brief, intense electric shock (Byrd, 1969(Byrd, , 1972Kelleher and Morse, 1968;McKearney, 1968McKearney, , 1969McKearney, , 1970McKearney, , 1972Morse, Mead, and Kelleher, 1967;Stretch, Orloff, and Dalrymple, 1968; Stretclh, Orloff, and Gerber, 1970 ation of the traditional distinction between "positive" and "negative" reinforcers, i.e., between events such as food, whose onset normally acts as a reinforcer, and electric shock, whose offset normally acts as a reinforcer.In some studies that have demonstrated maintained responding on schedules of response-produced shock, both shock and a period of time relatively free from shock were contingent on responding: the typical, periodic (fixed-interval) schedules generated discontinuous response rates, with the animals pausing for about half the fixed-interval before responding resumed. This pause may be taken as an indicator of a "functional timeout". Timeout (TO) from schedules of shock presentation has been shown to be reinforcing (e.g., Sidman, 1962;Verhave, 1962). The maintenance of responding on response-dependent shock schedules could therefore be due to the response-contingent period of time free of shock, rather than to the shock that precedes it. In the present experiment, the effect of timeout duration on responding under a variableinterval schedule of shock presentation was studied. METHOD SubjectsFour experimentally naive adult squirrel monkeys (Samiri sciureus) were housed individually and treated according to the general specifications described by Kelleher, Gill, Riddle, and Cook (1963). Food and water were available at all times in the monkeys' home cages.

Responding Maintained Under Intermittent Schedules of Electric‐shock Presentation: “Safety” or Schedule Effcts?

“…This view emphasizes the interactions among experimental histories, ongoing patterns of responding at the time at which an environmental event is introduced, and the schedule under which the event is introduced, as major determinants of whether presentation of a given stimulus will maintain responding-exemplifying the process of reinforcement; or 171 1981,36,[171][172][173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190] NUMBER 2 (SEPTEMBER) suppress responding-exemplifying the process of punishment. Other theorists (Eubanks, Killeen, Hamilton, & Wald, 1975;Hendry, 1969;Melvin, 1971;Stretch, 1972) have interpreted these results in terms of the concept of "safety." This viewpoint focuses on the discriminative (informative, cue) properties of shock when presented on Fl schedules as signaling a "safe period" during which no shocks are presented.…”

“…F. MALAGODI et al suppress responding-exemplifying the process of punishment. Other theorists (Eubanks, Killeen, Hamilton, & Wald, 1975;Hendry, 1969;Melvin, 1971;Stretch, 1972) have interpreted these results in terms of the concept of "safety." This viewpoint focuses on the discriminative (informative, cue) properties of shock when presented on Fl schedules as signaling a "safe period" during which no shocks are presented.…”

“…Hendry (1969) has suggested that electric shock becomes a conditioned positive reinforcer because of its informative and associative relation to either of these safe periods. Eubanks et al (1975), in interpreting their failure to maintain responding under variable-interval (VI) schedules of electricshock presentation, have suggested that a postshock safe period may be necessary for the chronic maintenance of behavior by shock presentation.…”

Theory of reinforcement schedules

“…This immediate safe time maintained robust responding despite there being no correlation between overall shock rate and the behavior of the rats. Eubanks et al (1975) were able to maintain performance on a VI schedule of response‐contingent shock as long as the shock was followed by a signaled timeout. As Denny found, response rate covaried with duration of the timeout.…”