Delayed Reinforcement and Delayed Choice in Symbolic Matching to Sample: Effects on Stimulus Discriminability

Abstract

Six pigeons were trained to peck a red side key when the brighter of two white lights (S,) had been presented on the center key, and to peck a green side key when the dimmer of two white lights (S2) had been presented on the center key. Equal frequencies of reinforcers were provided for the two types of correct choice. Incorrect choices, red side-key pecks following S2 presentations and green sidekey pecks following S, presentations, resulted in blackout. With 0-s delay between choice and reinforcement, the delay between sample presentation and choice was varied from 0 to 20 s. Then, with 0-s delay between sample presentation and choice, the delay between choice and reinforcement was varied from 0 to 20 s. Both types of delay resulted in decreased discriminability (defined in terms of a signal-detection analysis) of the center-key stimuli, but delayed choice had more effect on discriminability than did delayed reinforcement. These data are consistent with the view that the two kinds of delay operate differently. The effect of a sample-choice delay may result from a degradation of the conditional discriminative stimuli during the delay; the effect of a choice-reinforcer delay may result from a decrement in control by differential reinforcement.

Remembering: The role of extraneous reinforcement

“…When reinforcers for correct matching in DMTS are delayed, performance becomes less accurate (McCarthy & Davison, 1986Sargisson & White, 2003;Weavers, Foster, & Temple, 1998;Wilkie & Spetch, 1978). This is principally manifest as a reduction in initial discriminability, consistent with a time-independent effect of delayed reinforcement.…”

Writing and overwriting short-term memory

“…An equivalent equation was used by McCarthy and Davison (1984) and Wixted (1989) to fit experimental data on delayed matching-to-sampleexperiments, by Mazur (1984) to predict the effect of delayed reinforcers on the traces of choice responses, and by Laming (1992) as a fundamental forgetting function for BrownPeterson experiments. Alternate assumptions about the distribution of parameters give different average retention functions; Wickens (1998) provides a definitive review.…”

Remembering as discrimination in delayed matching to sample: Discriminability and bias

“…The reinforcer delay had a weaker effect when the discrimination was easy (with short retention intervals) than when the discrimination was difficult (with long retention intervals). The notion that the reduction in discriminability with increasing retention interval duration is caused by an increase in the delay of reinforcers from the sample (McCarthy & Davison, 1986;Weavers et al, 1998) was not supported by Sargisson and White's (2003) result. If it were the cause, varying the retention interval, with the delay between the sample and the reinforcer held constant, would result in a constant level of discriminability, which was not the case (Sargisson & White, 2003, Figure 4).…”

“…The result is consistent with the view that remembering in DMTS tasks is a discriminated operant in which increasing task difficulty increases sensitivity to reinforcement. Cox, 1976) and on DMTS tasks (McCarthy & Davison, 1986, 1991. It has been suggested that the decrease in discriminability with increasing retention interval in DMTS is partly due to the delay of reinforcement from the sample stimulus (McCarthy & Davison, 1986;Weavers, Foster, & Temple, 1998).…”

“…Cox, 1976) and on DMTS tasks (McCarthy & Davison, 1986, 1991. It has been suggested that the decrease in discriminability with increasing retention interval in DMTS is partly due to the delay of reinforcement from the sample stimulus (McCarthy & Davison, 1986;Weavers, Foster, & Temple, 1998). In other words, the retention interval acts as a delay to reinforcement, and as that delay increases, the link between the sample and the reinforcer is weakened.…”