Midsession reversals with pigeons: visual versus spatial discriminations and the intertrial interval (original) (raw)
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Learning & Behavior
The midsession reversal task involves a simultaneous discrimination in which choice of one stimulus (S1) is correct for the first 40 trials and choice of the other stimulus (S2) is correct for the last 40 trials of each 80-trial session. When pigeons are trained on the midsession reversal task, they appear to use the passage of time from the start of the session as a cue to reverse. As the reversal approaches, they begin to make anticipatory errors, choosing S2 early, and following the reversal they make perseverative errors, continuing to choose S1. Recent research suggests that anticipatory errors can be reduced (while not increasing perseverative errors) by reducing the probability of reinforcement for correct S2 choices from 100% to 20%. A similar effect can be found by increasing the response requirement for choice of S2 from one peck to ten pecks. In the present experiments, we asked if a similar effect could be attained by increasing the number of stimuli that, over trials, could serve as S2. Instead, in both experiments, we found that increasing the number of S2 stimuli actually increased the number of anticipatory errors. Several interpretations of this result are provided, including the possibility that attention to the variable S2 stimuli may have interfered with attention to the S1 stimulus.
Learning & Behavior, 2020
In the midsession reversal task, pigeons are trained on a simultaneous two-alternative discrimination in which S1 is correct for the first half of the session and S2 is correct for the second half of the session. Optimally, pigeons should choose S1 until it stops being correct and choose S2 afterward. Instead, pigeons anticipate S2 too early and continue choosing S1 even after the reversal. Research suggests that they attempt to time the reversal rather than use the feedback from the preceding response(s). Recently, there is evidence that performance is almost optimized by generating an asymmetry between S1 and S2. For example, pigeons' accuracy improves if correct S1 responses are reinforced 100% of the time, but correct S2 responses are reinforced only 20% of the time. Similarly, accuracy improves if S1 requires one peck but S2 requires 10 pecks. Accuracy does not improve, however, if the value of S1 is less than the value of S2. In the current experiment, we manipulated the magnitude of reinforcement. For the experimental group, correct responses to S1 were reinforced with five pellets of food and correct responses to S2 were reinforced with one pellet. For the control group, all correct responses were reinforced with three pellets. Consistent with the earlier findings, results indicated that there was a significant reduction in anticipatory errors in the experimental group compared with the control, and there was no significant increase in perseverative errors. Keywords Midsession reversal. Win-stay/lose-shift. Timing. Magnitude of reinforcement. Pigeons One measure of intelligence is the ability to use past experience when one encounters new learning. Harlow (1949) referred to this as learning to learn. In a variation of this principle, Mackintosh, McGonigle, Holgate, and Vanderver (1968) trained rats on a simple discrimination and then repeatedly reversed that discrimination. They found that the more reversals that were trained, the faster the rats acquired them. Rayburn-Reeves, Molet, and Zentall (2011; see also Cook & Rosen, 2010) trained pigeons on a version of the multiplereversal task, in which on each session the same stimulus (S1) is correct for the first half of the session, and the other stimulus (S2) is correct for the last half of each session. Following a large number of training sessions, several strategies may be used to near optimally perform this task. Animals could learn to count the number of trials to the reversal, but as most research has used an 80-trial session, that would be beyond the ability of most animals. Alternatively, one could choose S1
Pigeons’ use of cues in a repeated five-trial-sequence, single-reversal task
Learning & Behavior, 2013
We studied behavioral flexibility, or the ability to modify one's behavior in accordance with the changing environment, in pigeons using a reversal-learning paradigm. In two experiments, each session consisted of a series of five-trial sequences involving a simple simultaneous color discrimination in which a reversal could occur during each sequence. The ideal strategy would be to start each sequence with a choice of S1 (the first correct stimulus) until it was no longer correct, and then to switch to S2 (the second correct stimulus), thus utilizing cues provided by local reinforcement (feedback from the preceding trial). In both experiments, subjects showed little evidence of using local reinforcement cues, but instead used the mean probabilities of reinforcement for S1 and S2 on each trial within each sequence. That is, subjects showed remarkably similar behavior, regardless of where (or, in Exp. 2, whether) a reversal occurred during a given sequence. Therefore, subjects appeared to be relatively insensitive to the consequences of responses (local feedback) and were not able to maximize reinforcement. The fact that pigeons did not use the more optimal feedback afforded by recent reinforcement contingencies to maximize their reinforcement has implications for their use of flexible response strategies under reversal-learning conditions.
Midsession reversal learning: why do pigeons anticipate and perseverate?
Learning & Behavior, 2013
Past research has shown that when given a simultaneous visual-discrimination midsession reversal task, pigeons typically anticipate the reversal well before it occurs and perseverate after it occurs. It appears that they use the estimation of time (or trial number) into the session, rather than (or in addition to) the more reliable cue, the outcome from the previous trial (i.e., a win-stay/lose-shift response rule), to determine which stimulus they should choose. In the present research, we investigated several variables that we thought might encourage pigeons to use a more efficient response strategy. In Experiment 1, we used a treadle-stepping response, rather than key pecking, to test the hypothesis that reflexive key pecking may have biased pigeons to estimate the time (or trial number) into the session at which the reversal would occur. In Experiment 2, we attempted to make the point of reversal in the session more salient by inserting irrelevant trials with stimuli different from the original discriminative stimuli, and for a separate group, we added a 5-s time-out penalty following incorrect choices. The use of a treadle-stepping response did not improve reversal performance, and although we found some improvement in reversal performance when the reversal was signaled and when errors resulted in a time-out, we found little evidence for performance that approached the win-stay/lose-shift accuracy shown by rats.
Journal of the Experimental Analysis of Behavior
Our goal was to assess the role of timing in pigeons' performance in the midsession reversal task. In discrete-trial sessions, pigeons learned to discriminate between 2 stimuli, S1 and S2. Choices of S1 were reinforced only in the first half of the session and choices of S2 were reinforced only in the second half. Typically, pigeons choose S2 before the contingency reverses (anticipatory errors) and S1 after (perseverative errors), suggesting that they time the interval from the beginning of the session to the contingency reversal. To test this hypothesis, we exposed pigeons to a midsession reversal task and, depending on the group, either increased or decreased the ITI duration. We then contrasted the pigeons' performance with the predictions of the Learning-to-Time (LeT) model: In both conditions, preference was expected to reverse at the same time as in the previous sessions. When the ITI was doubled, pigeons' preference reversal occurred at half the trial number but at the same time as in the previous sessions. When the ITI was halved, pigeons' preference reversal occurred at a later trial but at an earlier time than in the previous sessions. Hence, pigeons' performance was only partially consistent with the predictions of LeT, suggesting that besides timing, other sources of control, such as the outcome of previous trials, seem to influence choice.
The Midsession Reversal Task with Pigeons: Effects of a Brief Delay Between Choice and Reinforcement
2020
OF THESIS THE MIDSESSION REVERSAL TASK WITH PIGEONS: EFFECTS OF A BRIEF DELAY BETWEEN CHOICE AND REINFORCEMENT During a midsession reversal task, the session begins with a simple simultaneous discrimination in which one stimulus (S1) is correct and the alternate stimulus (S2) is incorrect (S1+/S2-). At the halfway point, the discrimination reverses and S2 becomes the correct choice (S2+/S1-). When choosing optimally, a pigeon should choose S1 until the first trial in which it is not reinforced and then shift to S2 (win-stay/lose-shift). With this task pigeons have been shown to respond suboptimally by anticipating the reversal (anticipatory errors) and continuing to choose S1 after the reversal (perseverative errors). This suboptimal behavior may result from a pigeon’s relative impulsivity due to the immediacy of reinforcement following choice. In other choice tasks, there is evidence that the introduction of a short delay between choice and reinforcement may decrease pigeons’ impul...
Mechanisms of discrimination reversal in pigeons
Animal Behaviour, 1974
Groups of pigeons were trained on a successive discrimination procedure (multiple variableinterval, extinction schedule, with correction in Sand and then exposed to successive reversals, either daily, or less frequently. At asymptote the birds made more than 90 per cent of their responses to S+, and showed good transfer to a 'learning set' series. Three factors were involved in discrimination reversal performance: (a) a tendency to respond to only one of the two stimuli presented each day; (b) control of 'choice' by food delivery and by procedural cues; (c) a tendency to respond to the prior Sf (negative transfer). Transfer effects showed themselves in two main ways: (a) by impaired performance on the first reversal following manipulations that increased the salience in memory of S+ on a given day, such as a shift to a new pair of stimuli, or a gap (days off) in a series of daily reversals. The new-problem effect was quite robust, but the days-off effect was observed only when other controlling factors were relatively weak; (b) by impaired performance on the first reversal following learning set training interpolated into a series of reversals. Reversal performance seems to represent a balance among a number of controlling factors, and the factors involved may be different for different individuals, even though the final performances appear similar.
Animal Cognition, 1999
In the present study we investigated lateralization of color reversal learning in pigeons. After monocular acquisition of a simple color discrimination with either the left or right eye, birds were tested in a serial reversal procedure. While there was only a slight and non-significant difference in choice accuracy during original color discrimination, a stable superiority of birds using the right eye emerged in serial reversals. Both groups showed a characteristic 'learning-to-learn' effect, but right-eyed subjects improved faster and reached a lower asymptotic error rate. Subsequent testing for interocular transfer demonstrated a difference between pre-and post-shift choice accuracy in pigeons switching from right to left eye but not vice versa. This can be accounted for by differences in maximum performance using either the left or right eye along with an equally efficient but incomplete interocular transfer in both directions. Detailed analysis of the birds' response patterns during serial reversals revealed a preference for the right of two response keys in both groups. This bias was most pronounced at the beginning of a session. It decreased within sessions, but became more pronounced in late reversals, thus indicating a successful strategy for mastering the serial reversal task. Interocular transfer of response patterns revealed an unexpected asymmetry. Birds switching from right to left eye continued to prefer the right side, whereas pigeons shifting from left to right eye were now biased towards the left side. The results suggest that lateralized performance during reversal learning in pigeons rests on a complex interplay of learning about individual stimuli, stimulus dimensions, and lateralized response strategies.