Devaluation of Stimuli Contingent on Choice: Evidence for Conditioned Reinforcement

Abstract

Pigeons were presented a concurrent-chains schedule of reinforcement that had terminal links of equal duration. The initial links of the schedule were periodically interrupted by 15-s periods during which an extinction schedule was in effect. The extinction periods were presented on either a responsecontingent or a noncontingent basis. Relative response rate for the left alternative decreased when the extinction periods were accompanied by the left terminal-link stimulus. Relative response rate for the right alternative decreased when the extinction periods were accompanied by the right terminal-link stimulus. Relative response rate varied inversely with the frequency of presentation of the extinction periods but was unaffected by presence versus absence of the response contingency in the schedule of extinction-period presentation. Furthermore, relative response rate was unaffected by presentation of extinction periods accompanied by a novel stimulus. When the extinction periods were presented after reinforcement in the left terminal link instead of as interruptions of the initial links, relative response rate for the left alternative was reduced if the postreinforcemcnt extinction period was accompanied by the terminal-link stimulus for the left chain and reduced less if the extinction period was accompanied by the terminal-link stimulus for the right chain. The results demonstrate that the correlation between the terminal-link stimulus and extinction influenced the relative response rate in the initial link.Key words: conditioned reinforcement, stimulus value, extinction, concurrent chains, choice, pigeonsThe concept of a conditioned reinforcer entails an initially neutral stimulus acquiring properties of a reinforcer via a history of correlation with a primary reinforcer. One of the most common procedures to study the properties of conditioned reinforcers uses chain schedules in which the initial links are concurrently available (concurrent chains), and the terminal-link stimuli are correlated with different parameters of primary reinforcement. The critical measure is the relative rate of responding ("preference") strength can then be assessed by the effects of various parameters of the terminal-link schedules of primary reinforcement on preference.Early research with the concurrent-chains procedure suggested that preference was determined by the rate of reinforcement during the terminal links. For example, Herrnstein (1 964b) demonstrated that the relative rate of responding in initial links matched the relative rate of reinforcement on a variable-ratio schedule in one terminal link and a variable-interval (VI) schedule in the other despite the differing response requirements. But subsequent research demonstrated that a simple arithmetic average of the reinforcement rates in the two terminal links did not predict preference. Herrnstein (1964a), Fantino (1967), and Killeen (1968) compared fixed versus variable terminal-link schedules, and all reported higher rates in the initial link leading to the variable...

Choice, delay, probability, and conditioned reinforcement

“…Studies have shown that if the rate of primary reinforcement is equal for two alternatives, but one alternative delivers conditioned reinforcers at a higher rate, subjects will exhibit a preference for this alternative (Dunn, Williams, & Royalty, 1987;Williams & Dunn, 1991). However, rate of conditioned reinforcement is a difficult concept to define in a discretetrial procedure, and the studies demonstrating the effects of the rate of conditioned reinforcement have been conducted using concurrent-chain procedures.…”

“…This approach can also explain the results of studies that found a preference for whichever alternative delivered a higher rate of conditioned reinforcers, when the rate of primary reinforcement was equal for the two alternatives (Dunn et al, 1987;Williams & Dunn, 1991). For instance, Williams and Dunn used a concurrent-chain procedure with VI schedules as the initial links and FI 20-sec schedules as the terminal links.…”

Conditioned reinforcement: Neglected or outmoded explanatory construct?

“…As a result, it was impossible to determine whether the controlling variable was the response-reinforcer delay or the delay from the onset ofthe stimulus. It is now clear that it is the latter, because variations in the correlation of the stimulus with food (e.g., by providing separate extinction periods for the stimulus), while leaving constant the response-reinforcer delays, strongly affect preference (Dunn, Williams, & Royalty, 1987). There remains, however, the question as to why the value of a stimulus should be predicted only by the time to reinforcement associated with its onset, instead of by the rates of reinforcement occurring throughout the entire stimulus duration.…”

Basolateral amygdala lesions and sensitivity to reinforcer magnitude in concurrent chains schedules

“…These stimuli affect choice as conditioned reinforcers because they predict reinforcer delivery and can acquire conditioned value [26]. For example, in one study [27], pigeons chose between concurrent variable-interval (VI) 120-s initial links leading to illumination of a center key light (terminal link stimulus) that co-occurred with a fixed-interval (FI) 20-s terminal link ending in food delivery.…”