On the role of trial outcomes in delayed discriminations

Abstract

Delayed simple discriminations are typically retained more accurately over longer delays by pigeons than are delayed conditional discriminations (e.g., Honig & Wasserman, 1981). In two experiments, we investigated the extent to which trial outcomes contribute to this difference by comparing performances when all trials ended with food reinforcement versus when only half of the trials did. Experiment 1 showed that when food was presented on all trials, contingent upon either pecking or not pecking the test stimulus, levels of retention and rates of forgetting were comparable for these two tasks. By contrast, Experiment 2 showed better retention of delayed simple than delayed conditional discriminations when half of the trials ended with food and the other half in extinction. Furthermore, delayed simple discriminations were retained more accurately with food versus no-food outcomes than with food at the end of every trial, whereas the reverse was true for delayed conditional discriminations. These findings indicate that retention differences between these tasks are another instance of the differential outcomes effect. Honig and Wasserman (1981) and others (e.g., Cohen, Galgan, & Fuerst, 1986;Weisman, Bruce, & Beninger, 1987) have reported that working-memory performances are typically more accurate, and rates of forgetting slower, on delayed simple discriminations (DSDs) than on delayed conditional discriminations (DCDs). In a DSD, reinforcement for responding on the retention test is signaled solely by the stimuli presented at the beginning of the trial (i. e. , the initial stimuli), whereas in a DCD, reinforcement depends jointly upon the initial stimulus and the test stimulus.For example, in Experiment 1 of Honig and Wasserman (1981), separate groups of pigeons were trained on delayed go/no-go discriminations with red and green initial stimuli and vertical and horizontal test stimuli. For the DSD group, food was presented following the first test-stimulus response after 5 sec on all trials beginning with one hue, but was never presented on trials beginning with the other. For the DCD group, test-stimulus responses to one line orientation were reinforced following red but not green, whereas responses to the other orientation were reinforced following green but not red.When each group was later tested with delays ranging from 1-30 sec between initial stimulus offset and test Preparationof this manuscriptwas supportedby NSF Grant 86-06926 to Peter J. Urcuioli. Theauthorsthank Nicholas Ketterer, Beth Kraemer, Judy Tedlie, and SuzanneVanavermaete for runningthe subjects. Reprint requests may be addressed to Peter J. Urcuioli, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907. stimulus onset, DSD birds showed higher levels of discriminative performance and slower rates of forgetting than did DCD birds.These results are consistent with the view that subjects remember different events from trial to trial in these two tasks (i.e., the memory code differs). For instance, birds in a DSD mig...

Behavioral and associative effects of differential outcomes in discrimination learning

“…Anticipation of different response-contingent reinforcers can clearly serve a discriminative function. Indeed, anticipating the availability versus unavailability of a single reinforcer can be easily shown to exert a similar function (Urcuioli, DeMarse, & Zentall, 1998;Urcuioli & Zentall, 1990, 1992. In short, outcome expectancies can be part of the circumstances that direct action.…”

Matching-to-sample in pigeons: In the absence of sample memory, sample frequency is a better predictor of comparison choice than the probability of reinforcement for comparison choice

“…The differential-outcomes procedure is one in which there is one outcome following correct responses on one kind of trial (e.g., red sample trials) and a different outcome following correct responses on the other kind of trial (e.g., green sample trials). This procedure has been found to facilitate acquisition and enhance performance during delay testing (Peterson, Wheeler, & Trapold, 1980;Urcuioli, 1990;Urcuioli & Zentall, 1990). Urcuioli used a design that was similar to the design used in the present experiments.…”

Differential outcomes and many-to-one matching: Effects of correlation with correct choice

“…For example, pigeons acquire two-altemative matchingto-sample (MTS) much more rapidly when the correct choice following each sample stimulus producesa unique outcome than when it produces either the same outcome on all trials or each outcome equally often (Brodigan & Peterson, 1976;Edwards, Jagielo, Zentall, & Hogan, 1982;Linwick, Overmier, Peterson, & Mertens, 1988;Peterson, 1984;Peterson, Linwick, & Overmier, 1987;Peterson, Wheeler, & Trapold, 1980;Santi & Roberts, 1985a;Urcuioli, 1990;Williams, Butler, & Overmier, 1990). The same effeet also occurs in related tasks such as successive matehing (DeLong & Wasserman, 1981;Honig, Matheson, & Dodd, 1984; see also Urcuioli & Zentall, 1990). My purpose in the present study was to investigate the processes by which this differentialoutcomes effect (DOE) might 00 produced.…”