Enhancement of pigeons’ conditional discrimination performance by expectancies of reinforcement and nonreinforcement

Abstract

Prior work has shown that when the separate correct responses of a conditional discrimination are followed by different reinforcing outcomes, performance is enhanced relative to that obtained under the conventional, single-reinforcer procedure. Four experiments with pigeons yielded the analogous finding when the different outcomes were reinforcement and explicit nonreinforcement. Controls indicated that the results could not be attributed to the effects of intermittent reinforcement, to possible differences in cue duration, or to a variety of potential sources of conditioned reinforcement. An interpretation in terms of expectancy learning is proposed. Trapold (1970) originally demonstrated what we will refer to in this paper as the differential outcomes effect (DOE). He found that rats learn a conditional discrimination (i.e., if stimulus S.. then response R 1 is correct, but if S2, then R 2 is correct) faster when correct responses to S, are consistently followed by reinforcing outcome 0 1 (e.g., sucrose solution) and correct responses to S2 are consistently followed by a different outcome O 2 (e.g., food pellets) than if correct responses to S, and S2 are both reinforced by the same outcome. Trapold hypothesized that the DOE occurs because (1) when S, and S2 are each followed by a unique outcome event, subjects learn an expectancy of 0 1 to S, and an expectancy of O 2 to S2' and (2) these different expectancies provide an additional source of differential stimulation that can assume stimulus control over the choice behavior. In contrast, subjects which receive the same outcome for correct responding to S, and S2 learn the same expectancy to Sl and S2' and hence do not have available this additional source of potential differential stimulus control over R1 and R2.Trapold provided additional support for this theo- retical analysis by showing that subjects who are pretrained so as to preestablish the expectancies involved in a subsequent differential-outcomes conditional discrimination problem learn that problem faster than subjects pretrained to expect the wrong outcome. Wielkiewicz (1972, 1976) extended Trapold's findings by showing a DOE for food reward outcomes of different delays and different magnitudes in rats. Overmier, Bull, and Trapold (1971) demonstrated a DOE in dogs when the differential outcomes were avoidance of electric shocks to different loci on the body. Brodigan and Peterson (1976) and Peterson, Wheeler, and Armstrong (1978) found a DOE with pigeons using food and water as the different outcomes. These latter studies also provided considerable additional support for the assumption that the DOE is mediated by differential outcome expectancies which function as part of the discriminative stimulus complex to which the correct response becomes learned. Specifically, they showed that the DOE is much more profound when a delay is inserted between the offset of the conditional cue (S, or S2) and the opportunity to choose between R 1 and R 2. With a standard procedure, insertion of such a delay of ev...

Delayed discriminations in the pigeon: The role of within-trial location of conditional cues

“…They may have developed an expectancy of reward or no reward based upon the initial stimuli; this could have served as a differential cue at the time of the test stimulus. Recent work by Peterson and his associates Peterson, Wheeler, & Trapold, 1980) demonstrates that such outcome expectancies enhance working memory. In some of their experiments, one of the differential outcomes is actually no reward with the opportunity to advance to the next trial.…”

Effects of sample duration, retention interval, and passage of time in the test on pigeons’ matching-to-sample performance

“…Figure 7 shows the composite delay gradient that results from another discrimination index: DR = [1-.5(rate of response on nonmatching trials)/(rate of response on matching trials)] X 100-(cf. Wasserman, 1976 (Grant, 1981;Honig, 1978;Honig & Wasserman, 1981;Peterson, Wheeler, & Armstrong, 1978;Peterson, Wheeler, & Trapold, 1980). How could prospection be applied to performance in the go/no-go DMTS paradigm?…”

Reinforcement expectancy and trial spacing effects in delayed matching-to-sample by pigeons

“…A number of studies have demonstrated enhanced acquisition of discriminationand superior memory performance in pigeons when sample stimuli were associated with different trial outcomes (DO) following correct responding relative to when the outcomes were nondifferential (NDO). The DO effect has been demonstratedwith qualitativelydifferent reinforcers (Brodigan & Peterson, 1976;Edwards,Jagielo, Zentall, & Hogan, 1982;Honig, Matheson, & Dodd, 1984;Peterson, Wheeler, & Armstrong, 1978), reward versus no reward (Peterson, 1984;Peterson, Wheeler, & Trapold, 1980), and differential probability of reward (DeLong & Wasserman, 1981). Several explanations of the DO effect have been proposed and tested.…”