Response Rate Viewed as Engagement Bouts: Resistance to Extinction

Abstract

Rats obtained food pellets by nose poking a lighted key, the illumination of which alternated every 50 s during a session between blinking and steady, signaling either a relatively rich (60 per hour) or relatively lean (15 per hour) rate of reinforcement. During one training condition, all the reinforcers in the presence of the rich-reinforcement signal were response dependent (i.e., a variable-interval schedule); during another condition only 25% were response dependent (i.e., a variable-time schedule operated concurrently with a variable-interval schedule). An extinction session followed each training block. For both kinds of training schedule, and consistent with prior results, response rate was more resistant to extinction in the presence of the rich-reinforcement signal than in the presence of the lean-reinforcement signal. Analysis of interresponse-time distributions from baseline showed that differential resistance to extinction was not related to baseline differences in the rate of initiating response bouts or in the length of bouts. Also, bout-initiation rate (like response rate) was most resistant to extinction in the presence of the rich-reinforcement signal. These results support the proposal of behavioral momentum theory (e.g., Nevin & Grace, 2000) that resistance to extinction in the presence of a discriminative stimulus is determined more by the stimulus-reinforcer (Pavlovian) than by the stimulus-response-reinforcer (operant) contingency.

Resistance to Change of Responding Maintained by Unsignaled Delays to Reinforcement: A Response‐bout Analysis

“…If responding did consist of two processes, one possible reason that the patterns of responding were not consistently bimodal in the present experiment may have been due to relatively high response rates. A large majority of the log survivor functions fell within 5 to 7 s (see Figure 3; see also Davison, 2004), whereas functions from previous experiments with rats nose poking have ranged anywhere from 20 to 250 s (see Shull, 2004;Shull et al, 2002). Any deviations from simple double-exponential functions that would appear minor under less constrained ranges could become magnified under the ranges found in the present experiment.…”

“…Examining underlying response structure using log survivor plots and a double-exponential model (Shull & Grimes, 2003) failed because responding was not consistently composed of two separate modes (see Figure 3). Even when responding did appear to occur in bouts (e.g., for Pigeon 217), the log survivor functions did not conform to simple double exponential functions that previously have been observed with rats lever pressing and nose poking for food (e.g., Shull & Grimes, 2003;Shull et al, 2001Shull et al, , 2002Shull et al, 2004).…”

“…Yet given the fact that within-bout rates were reliably above 60 per min during disruption (see Appendix), it is unlikely that the constraints could account for all the constancy found here. Disruption of responses per bout was significantly correlated with disruption of overall response rates, F(1, 49) 5 8.64, p 5 0.005, although this correlation with disruption in overall response rates was much smaller than with bout-initiation rates (see also Shull, 2004;Shull et al, 2002). Thus, disruptions of overall response rates were strongly related to bout-initiation rate, weakly related to changes in responses per bout, and unrelated to changes in within-bout rates.…”

“…In rats nose poking and lever pressing for food, differences in reinforcement rates have been shown to affect bout-initiation rates, whereas adding a small ratio response requirement to the end of a VI schedule increases within-bout responding (Shull, Gaynor, & Grimes, 2001Shull & Grimes, 2003). Conditions of disruption have been shown to decrease boutinitiation rates relative to baseline, whereas within-bout responding tends to be less affected (Shull, 2004;Shull et al, 2002). The effects of delayed reinforcement on bout initiations and within-bout responding have not been examined either during baseline conditions or under conditions of disruption.…”

“…Nevertheless, other investigators have shown that changes in overall response rates are due to changes in long rather than short IRTs (Blough, 1963;Schaub, 1967) and, therefore, the IRT-cutoff method may provide at least a general picture of how the present manipulations affected response patterns. Consistent with Shull et al (2002), we selected 1 s as the cutoff criterion for all the pigeons. Thus, responses ending in IRTs greater than 1 s were classified as bout initiations, whereas responses ending in IRTs equal to or less than 1 s were classified as within-bout responses.…”