SCHEDULE‐INDUCED ESCAPE FROM FIXED‐INTERVAL REINFORCEMENT¹

Abstract

Pigeons trained to peck one of two keys for food were exposed to an ascending and descending series of fixed-interval values. A response on the second key produced an escape period consisting of a visual stimulus change. During escape periods, the fixedinterval timer continued to operate and even if it timed out, a response on the food key would not operate the feeder unless preceded by an escape-key response that terminated the escape condition. As the fixed-interval schedule was increased logarithmically through six values from 30 to 960 sec, the percentage of session time spent in escape as well as the frequency, duration, and rate of escape increased to a maximum and then decreased. One subject did not develop escape behavior to any significant degree. For all pigeons, escapes usually occurred after, rather than before, reinforcement.When rats and pigeons respond on fixedratio schedules of reinforcement, they occasionally respond on a second operandum producing escape periods during which extinction and a correlated stimulus are in effect (Appel, 1963;Azrin, 1961;Thomas and Sherman, 1965;Thompson, 1964Thompson, , 1965Zimmerman and Ferster, 1964). When pigeons were allowed to control the durations of these escape periods, Azrin (1961) observed that the percentage of session time spent in escape, or timeout, increased monotonically as a function of the increasing response requirement of the fixedratio food schedule. Similarly, other investigators using rats (Thompson, 1964) as well as pigeons (Appel, 1963;Thomas and Sherman, 1965;Thompson, 1965) have reported that the frequency and duration of escapes increased as a function of the fixed-ratio schedule value.Typically, escape periods occur during the characteristic postreinforcement pause of fixedratio schedules. It has been suggested (Azrin, 1961;Thompson, 1964Thompson, , 1965 Zimmerman and Ferster (1964), no monotonic relationship was obtained between fixed-ratio response requirement and amount of escape or timeout behavior. Thomas and Sherman (1965) also observed a two-valued bitonic function relating fixed-ratio response requirement and number of timeouts for one of three pigeons. Similar bitonic functions have been observed with other schedule-induced behaviors. Scheduleinduced attack in pigeons (Flory, 1969) and scheduled-induced polydipsia in rats (Flory, 1971;Hawkins, 1967;Segal, Oden, and Deadwyler, 1965)

Escape From Serial Stimuli Leading to Food

“…The authors suggested that the frequency of aggression be used as an index of aversiveness, although they obviously used the latter term in some sense more general than we have. T. G. Brown and Flory (1972;see also Flory, 1969) found that pigeons pecked an auxiliary key when that response turned off the color accompanying a fixed-interval schedule, doing this most frequently during the first quarter of the interval and fairly often during the second. The birds also restored the FI color by pecking the same key.…”

Stimulus control of behavior during the postreinforcement pause of FI schedules

“…The interval-initiating response on response-initiated FI schedules is always preceded by a pause (Chung & Neuringer, 1967;Mechner et al, 1963;Shull, 1970), and responses to escape from stimuli associated with FI schedules seem to occur some time after reinforcement (see Figure 5 of Brown & Flory, 1972).…”

“…Brown and Flory (1972) found that pigeons would respond to change the color of the key light and turn off the houselight during fixed intervals ranging from 30 to 960 sec, although interval duration was not shortened by this response. Rilling et al (1%9) found that pigeons would peck a key to produce a blackout and thus escape from a stimulus associated with extinction.…”

Functional differentiation of adjunctive drinking and wheel running in rats

“…For example, one of the characteristics of adjunctive behavior is supposed to be the existence of an "effective range" of consummatory rates which facilitate adjunctive activities: Measures of schedule-induced polydipsia (Falk, 1966;Flory, 1971), schedule-induced aggression (Flory, 1969), and schedule-induced escape (Brown & Flory, 1972) have all been shown to increase as rates of food delivery are increased to some inter mediate value (roughly between 15 and 30 presentations/h), and thereafter to decrease as food rates are further increased. Escape and aggression were measured in response/minute.…”