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

Separate groups of rats were trained and tested on asymmetrically and symmetrically reinforced successive delayed matching-to-sample (DMTS) or delayed discrimination (DD) tasks in Experiment 1. Each rat received training and testing on symmetrically reinforced DMTS and DD tasks in Experiment 2. The only difference between each task was that the rats had to respond correctly to a light or tone test stimulus, S2' if it matched a light or tone sample stimulus, S" in DMTS, but could respond to either S2 if S, had been a particular stimulus in DD. Only correct leverpresses were reinforced in the asymmetrically reinforced version of each task. Both correct presses and correct omissions were reinforced in the symmetrically reinforced version of each task. Response biases to leverpress during tests for delayed responding to S. were reduced in both symmetrically reinforced tasks, but only in the DD task did such contingencies produce consistently poorer performance in responding to either S. in Experiment 1. Declines in accuracy of performance that occurred in both experiments were greater to the visual than to the auditory S, only in the DMTS tasks with increased intervals between S, and S2. A third experiment, in which rats had to respond to S2 if it matched S. (DMTS) or if S2 mismatched S. (DMmTS), was carried out. Modality of S. similarly affected accuracy of delayed responding in each task, as in the first two experiments. Methodological and theoretical implications of these results are discussed in terms of Honig and Thompson's (1982) dual-process theory of working memory.Honig and Thompson (1982) distinguish between retrospection, memory of a previous stimulus, and prospection, retention of an instruction for future responding to the previous stimulus, in short-term memory of nonhuman animals.

Section: Discussioncontrasting

confidence: 57%

“…ditional than in delayed simple discrimination, in pigeons (Honig & Wasserman, 1981;Smith, 1967). Increasing retention intervals after the sample stimuli also disrupts matching more than does increasing them after the conditional stimulus, in pigeons (Honig & Dodd, 1983;Weisman & DiFranco, 1981).…”

mentioning

confidence: 99%

Retrospective and prospective short-term memory in delayed response tasks in rats

Cohen

Galgan

Fuerst

1986

“…Therefore, most of the forgetting seems to occur during the shorter MI within each distribution. This is by no means a necessary aspect of the MI distribution effect, which has been obtained previously with declining memory functions (Honig & Dodd, 1983;Honig & Wasserman, 1981).…”

Section: Discussionmentioning

confidence: 93%

Memory interval distribution effects in pigeons

Honig

1987

Self Cite

Pigeons were trained with two concurrent delayed conditional discriminations that involved different distributions of memory intervals, namely 1 and 5 sec in the "short" and 5 and 10 sec in the "long" distribution. Memory for the initial stimulus was much better after 5 sec in the short distribution than in the long one. The memory functions between the intervals within each distribution were essentially flat. These findings were replicated in a second study that involved differential outcomes; this procedure enhanced memory generally within trials so that memory intervals of 1, 9, and 19 sec could be used, with 9 sec serving as the common memory interval. The findings are interpreted on the basis of the subject's expectation of the likely duration of the upcoming memory interval and the associated delay of reinforcement.In most working memory paradigms, stimuli that occur at the beginning of a trial can serve several functions. The discriminative stimuli, or initial stimuli, as I will call them, provide cues to the subject for the correct response to the test stimulus or test stimuli presented after the memory interval (MI). This information is formally sufficient for good performance, but working memory is modulated by other information provided at the same time. The most familiar is the association of different outcomes with the initial stimuli. This procedure enhances working memory. The differential outcomes effect is based upon anticipation of trial outcomes as mediators of improved performance (for reviews, see Honig & Thompson, 1982;Peterson, 1984;Peterson & Trapold, 1980). Working memory is also affected by directed forgetting procedures (Grant, 1981; Maki, 1981;Stonebraker & Rilling, 1981). An "instantial" cue presented together with the initial stimulus on some trials indicates that the test stimulus or stimuli will be omitted following the MI. This results in a failure of performance on probe trials in which the test stimuli are actually presented. A reasonable explanation of the failure to remember the initial stimulus is that the subject anticipates the omission of reward when the instantial cue is presented.Instantial cues also affect working memory when they signal specific MIs. This effect has been studied much less extensively than the differential outcomes effect or directed forgetting. Wasserman, Grosch, and Nevin (1982) have provided a clear example. In two experiments, they trained pigeons on a delayed conditional discrimination, in which orange and green served as the initial stimuli and as the singly presented test stimuli. MI duration was signaled in a correlated condition by horizontal and vertical lines that were superimposed on the colors and extended throughout the MI. In an uncorrelated condition, the same stimuli were randomly associated with the different MIs. Memory functions were steeper in the correlated condition. Occasional probe trials were carried out in the latter condition, in which the wrong MI followed the horizontal or vertical lines. As a result, the pigeons performed...

“…Honig & Dodd, 1983), as shown by the dissociations between rates of initial acquisition and retention. For example, Group SD acquired its discrimination faster than did Group CD in both Experiments 1 and 2, yet retention performances in these two groups were virtually equivalent.…”

Section: Discussionmentioning

confidence: 99%

On the role of trial outcomes in delayed discriminations

Urcuioli

Zentall

1990

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...