Recent experiments with rats suggest that they show episodic-like or what-where-when memory for a preferred food found on a radial maze. Although memory for when a salient event occurred suggests that rats can mentally travel in time to a moment in the past, an alternative possibility is that they remember how long ago the food was found. Three groups of rats were tested for memory of previously encountered food. The different groups could use only the cues of when, how long ago, or when + how long ago. Only the cue of how long ago food was encountered was used successfully. These results suggest that episodic-like memory in rats is qualitatively different from human episodic memory.

In 4 experiments, the authors asked whether pigeons (Columba livia) would show metamemory by choosing to study a sample stimulus before taking a memory test. In Experiments 1a-1c, pigeons chose between cues that led either to exposure to a sample stimulus or directly to the comparison test stimuli without seeing the sample in a delayed matching-to-sample task. The same choice was used in Experiment 2 to see whether pigeons would take a reminder when memory of the sample was weak. In Experiments 3 and 4, pigeons' responses led to either a choice between red and green side keys with a sample present to guide the choice or a choice with no sample present. The findings of all of these experiments suggest the absence of metamemory in pigeons.

It has been shown previously that pigeons make surprising errors on a visually based midsession reversal task (Cook & Rosen, 2010; Rayburn-Reeves, Molet, & Zentall, 2011). We trained birds with red and green sidekeys, with one color rewarded in the first 40 trials (S1) and the other color rewarded in the latter 40 trials (S2). Importantly, in Phases 1 and 3, red and green were always presented on the same side, whereas in Phase 2 sidekeys were presented on the left and right equally often. In Phases 2 and 3, probe sessions with intertrial intervals (ITIs) longer or shorter than the training intertribal interval (ITI) were interjected among baseline sessions. Results showed that pigeons presented with visual-only cues used interval duration since the beginning of the session to predict when the reversal of reward contingency would occur, but pigeons presented with color and spatial dimensions confounded for predicting reward tended to use a more optimal reward-following strategy of choice based on local reinforcement.

Pigeons (Columba livia) produce many anticipatory and perseverative errors on discrimination tasks with a reversal of reward contingencies partway through the session. Prior comparative research has suggested that rats (Rattus norvegicus) do not show the same number of errors and produce results that more closely resemble those of humans. We examined pigeons' performance on a visual-spatial discrimination with the reversal point randomized within the session and found that they showed remarkably few errors. When these subjects were split into groups with the contingencies for reward unconfounded, the birds in the spatial-contingency group maintained their performance, and those in the visual-contingency group made many more anticipatory and perseverative errors. We also examined the performance of naïve pigeons on a spatial midsession reversal task and found a pattern of results similar to those shown by pigeons that had previously been trained on a visual-spatial reversal procedure. Finally, we studied rats on a T-maze using a spatial-discrimination midsession reversal task and found that the rats showed a large number of anticipatory and perseverative errors. Near-perfect performance on the midsession reversal task appears to be subject to the ability of the animal to orient spatially during the intertrial interval, rather than being due to broad species differences.

No abstract

In a 2-stimulus visual discrimination choice task with a reversal in reward contingencies midway through each session, pigeons produce a surprising number of both anticipatory errors (i.e., responding to the second-correct stimulus before the reversal) and perseverative errors (i.e., responding to the first-correct stimulus after the reversal). Here, we used a go/no-go version of the task to examine the degree to which these errors can be attributed to failure to inhibit incorrect responses near the reversal. We presented pigeons with either a green or red stimulus (randomized across trials), with pecks to 1 reinforced with food and pecks to the other stimulus leading to a 10-s time-out; the reward versus time-out contingencies reversed after 40 trials. Pigeons rarely withheld responses when reward was provided for pecking, but produced many incorrect pecks near the reversal. Subsequent experiments examined these errors with longer sessions and multiple reversals, as well as on choice tasks. Our results suggest that pigeons' errors may be due to an inability to inhibit incorrect responses rather than a deliberate choice of the incorrect stimulus on simultaneous discrimination midsession reversal procedures. Results suggest that pigeons learned independent rules about the 2 stimuli, and that training with multiple reversals changed the rules that governed pigeons' responding. (PsycINFO Database Record

Extreme stimuli are often more salient in perception and memory than moderate stimuli. In risky choice, when people learn the odds and outcomes from experience, the extreme outcomes (best and worst) also stand out. This additional salience leads to more risk-seeking for relative gains than for relative losses-the opposite of what people do when queried in terms of explicit probabilities. Previous research has suggested that this pattern arises because the most extreme experienced outcomes are more prominent in memory. An important open question, however, is what makes these extreme outcomes more prominent? Here we assess whether extreme outcomes stand out because they fall at the edges of the experienced outcome distributions or because they are distinct from other outcomes. Across four experiments, proximity to the edge determined what was treated as extreme: Outcomes at or near the edge of the outcome distribution were both better remembered and more heavily weighted in choice. This prominence did not depend on two metrics of distinctiveness: lower frequency or distance from other outcomes. This finding adds to evidence from other domains that the values at the edges of a distribution have a special role. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

In 2 experiments, rats were trained to press a centrally located lever that delivered immediate food reinforcement and turned on a light signal that indicated the location of a further food reward. After rats learned to press the lever and use the light cue to find food, immediate reinforcement for lever pressing was discontinued. In Experiment 1, rats continued to press the lever for information about the location of reward in a T-maze, but control groups yoked to the experimental group for amount of reward, and conditioned reinforcement showed complete extinction of lever pressing. Rats tested on an 8-arm radial maze in Experiment 2 also continued to press a lever that did not yield immediate reinforcement but provided a light cue indicating which randomly chosen arm of the maze contained food; lever pressing declined significantly, however, when the same arm contained food on every trial. Comparisons of testing conditions between and within experiments suggested that probability of lever pressing increased as the amount of information gained increased. The comparative implications of these findings for metacognition are discussed.