Rat spatial memory and foraging on dual radial mazes.

Three experiments are reported that used a new test of spatial memory in rats. The apparatus used was dual eight-arm radial mazes that were connected at one arm of each maze, with a start arm and doors to each maze. Rats could be forced to go to one maze or the other or could make a free choice between mazes. In Experiment 1, rats formed reference memory for the arm containing food on one maze but had food randomly placed on different arms over trials on the other maze. In Experiment 2, rats formed working memory for the arm containing food on one maze but not the other. In Experiment 3, food location changed randomly among trials on both mazes, but one maze contained a cue for the location of food. Rats used reference and working memory to go directly to the food arm on one maze but found food only after searching several arms on the other maze. Most importantly, when given free-choice trials rats developed a significant preference for the maze where they knew the location of food reward or found the cue indicating the location of reward. We suggest these findings may be best interpreted by rats applying two successive rules: (1) choose the maze that leads to the most immediate reward, and (2) use extramaze or intramaze cues to find reward location on the maze.

An operant analog of food caching in the pigeon (Columba livia).

Although pigeons do not naturally cache and recover food items as found in members of the corvid and parid families, an operant analog of food caching and recovery in pigeons was studied in four experiments. Pigeons were trained to peck a caching key that added a fixed increment of time to the final duration of reinforcement obtained by pecking a payoff key. The same key served as the caching and payoff keys in Experiment 1, but separate caching and payoff keys were used in Experiments 2-4. In Experiments 2-3, each peck on a left red caching key added 0.5 s of reinforcement earned by pecking a right white payoff key. In Experiment 4, red or green caching keys appeared on different trials, with 0.5 s of reinforcement earned for pecking the red key and 1.0 s of reinforcement earned for pecking the green key. Pigeons showed an increased number of pecks on the caching key over ten sessions in Experiments 1-3 and more pecks on the green caching key than on the red caching key in Experiment 4.

No evidence for future planning in Canada jays (Perisoreus canadensis).

In the past 20 years, research in animal cognition has challenged the belief that complex cognitive processes are uniquely human. At the forefront of these challenges has been research on mental time travel and future planning in jays. We tested whether Canada jays (Perisoreus canadensis) demonstrated future planning, using a procedure that has produced evidence of future planning in California scrub-jays. Future planning in this procedure is caching in locations where the bird will predictably experience a lack of food in the future. Canada jays showed no evidence of future planning in this sense and instead cached in the location where food was usually available, opposite to the behaviour described for California scrub-jays. We provide potential explanations for these differing results adding to the recent debates about the role of complex cognition in corvid caching strategies.

The olfactory capability of dogs to discriminate between different quantities of food.

A previous study failed to find evidence that dogs could use olfactory cues to discriminate between 1 and 5 hot dog slices presented on a single trial (Horowitz et al., Learning and Motivation, 44, 207-217, 2013). In the experiments reported here, multiple trials were used to test dogs' ability to use olfaction to choose one of two opaque containers under which a larger number of food items was placed. In Experiment 1, dogs chose between 1 and 5 hot dog slices. In Experiments 2 and 3, we examined dogs' ability to discriminate between numbers of hot dog slices that varied in the numerical distance and the ratio between the smaller and larger quantities. Experiment 4 explored olfactory discrimination between quantities of a different food, dog kibble. Experiments 1-3 all showed that dogs used olfactory stimuli to choose the larger number of hot dog slices, but Experiments 2 and 3 revealed no effects of distance or ratio between numerical quantities. In Experiment 4, dogs failed to discriminate between 1 and 5 pieces of dog kibble. Factors that allow dogs to use olfactory cues to discriminate between quantities are discussed.

Addition and subtraction by honeybees.

Howard, Avargues-Weber, Garcia, Greentree, and Dyer (Science Advances, 5,1-6, 2019) report experiments in which honeybees initially shown a number of shapes could subsequently choose a pattern that added or subtracted one from that number. Further, the operations of addition and subtraction were cued by the colors of the shapes.

The role of context in animal memory.

Past research has shown that testing memory in the same context in which the memory was encoded leads to improved retention relative to testing memory in a new context. Context-dependent memory is directly related to the extent to which the encoding context can be reproduced. An experiment with pigeons is reported in which the context was a colored house-light that completely enveloped the learning and testing contexts. Under this condition, perfect retention of a visual discrimination that reversed at midsession was shown. Beyond reactivation of memory, new research with pigeons suggests that context provides access to different working and reference memory systems. Finally, experiments are reported that suggest context may selectively access information about features from the different dimensions of place, color, and time.

Pigeons play the percentages: computation of probability in a bird.

The ability to compute probability, previously shown in nonverbal infants, apes, and monkeys, was examined in three experiments with pigeons. After responding to individually presented keys in an operant chamber that delivered reinforcement with varying probabilities, pigeons chose between these keys on probe trials. Pigeons strongly preferred a 75% reinforced key over a 25% reinforced key, even when the total number of reinforcers obtained on each key was equated. When both keys delivered 50% reinforcement, pigeons showed indifference between them, even though three times more reinforcers were obtained on one key than on the other. It is suggested that computation of probability may be common to many classes of animals and may be driven by the need to forage successfully for nutritional food items, mates, and areas with a low density of predators.

Release from proactive interference in rat spatial working memory.

A three-phase procedure was used to produce proactive interference (PI) in one trial on an eight-arm radial maze. Rats were forced to enter four arms for reward on an initial interference phase, to then enter the four remaining arms on a target phase, and to then choose among all eight arms on a retention test, with only the arms not visited in the target phase containing reward. Control trials involved only the target phase and the retention test. Lower accuracy was found on PI trials than on control trials, but performance on PI trials significantly exceeded chance, showing some retention of target memories. Changes in temporal and reward variables between the interference, target, and retention test phases showed release from PI, but changes in context and pattern of arm entry did not. It is suggested that the release from PI paradigm can be used to understand spatial memory encoding in rats and other species.

Memory systems in the rat: effects of reward probability, context, and congruency between working and reference memory.

The interaction of working and reference memory was studied in rats on an eight-arm radial maze. In two experiments, rats were trained to perform working memory and reference memory tasks. On working memory trials, they were allowed to enter four randomly chosen arms for reward in a study phase and then had to choose the unentered arms for reward in a test phase. On reference memory trials, they had to learn to visit the same four arms on the maze on every trial for reward. Retention was tested on working memory trials in which the interval between the study and test phase was 15 s, 15 min, or 30 min. At each retention interval, tests were performed in which the correct WM arms were either congruent or incongruent with the correct RM arms. Both experiments showed that congruency interacted with retention interval, yielding more forgetting at 30 min on incongruent trials than on congruent trials. The effect of reference memory strength on the congruency effect was examined in Experiment 1, and the effect of associating different contexts with working and reference memory on the congruency effect was studied in Experiment 2.

Rats respond where it counts.

Taniuchi, Sugihara, Wakashima, and Kamijo (2016) report the surprising finding that rats can transfer numerical discrimination to novel objects. Further experiments show that rat numerical discrimination is flexible, as it can both count homogeneous and heterogeneous objects and omit an odd object.

A three-stimulus midsession reversal task in pigeons with visual and spatial discriminative stimuli.

In a two-stimulus visual discrimination task with a reversal in reward contingencies midway through each session, pigeons produce a surprising number of both anticipatory (i.e., before the reversal) and perseverative (i.e., after the reversal) errors. In the current work, we examined pigeons' (Columba livia) patterns of responding on a 90-trial, three-stimulus visual or spatial discrimination task with two changes in reward contingency (one after Trial 30 and one after Trial 60) during each session. On probe sessions where pecking the first-correct stimulus was rewarded for the first 60 rather than 30 trials, pigeons on a spatial discrimination pecked the first-correct stimulus until it was no longer rewarded, while visual discrimination birds ceased responding to the first-correct stimulus even while it was still being rewarded. On probe sessions where the onset of the first trial was delayed 7 min, pigeons' performance on the visual discrimination was disrupted by the interval delay, but performance in the spatial condition was more similar to baseline. Pigeons use different strategies (temporal control vs. local reinforcement) on midsession reversal tasks with visual versus spatial stimuli, suggesting that they are selectively permeable to changes in information (global vs. local reinforcement rates).

Pigeons rank-order responses to temporally sequential stimuli.

We explored pigeons' ability to learn a particular sequence of stimuli in which the durations of each stimulus varied among trials, where the first response at the end of the sequence was reinforced. In Experiment 1A, we found that pigeons failed to use the whole sequence of three stimuli to predict food reinforcement, and instead responded only to the third, "rewarded" stimulus. When rewarded (1-2-3) and nonrewarded (2-1-3) sequences were used in a go/no-go procedure in Experiment 1B, however, pigeons showed a tendency to rank-order responding, with higher response rates to the second than to the first stimulus, as well as lower response rates to the third stimulus on nonrewarded-sequence trials. In Experiment 2, pigeons showed rudimentary rank-ordering of five stimuli in sequence, with lower responding to the final stimulus on nonrewarded trials, even when the sequence presented differed from the rewarded sequence only in a reversal of the second and third stimuli. Pigeons were capable of using ordinal information in a temporal task, but only when that information was easily discriminable and led to explicit consequences (i.e., rewarded vs. nonrewarded sequences).

Theory of mind in dogs: is the perspective-taking task a good test?

Udell, Dorey, and Wynne (in press) have reported an experiment in which wolves, shelter dogs, and pet dogs all showed a significant preference for begging from a person who faced them (seer) over a person whose back was turned to them (blind experimenter). On tests with the blind person's eyes covered with a bucket, a book, or a camera, pet dogs showed more preference for the seer than did wolves and shelter dogs. We agree with the authors' position that most of these findings are best explained by preexperimental learning experienced by the subjects. We argue, however, that the perspective-taking task is not a good test of the domestication theory or of the theory of mind in dogs. The problem we see is that use of the perspective-taking task, combined with preexperimental learning in all the subjects, strongly biases the outcome in favor of a behavioral learning interpretation. Tasks less influenced by preexperimental training would provide less confounded tests of domestication and theory of mind.

Irrational behavior in dogs (Canis lupus familiaris): A violation of independence from irrelevant alternatives.

We tested dogs for a violation of independence from irrelevant alternatives, which would indicate irrational behavior. In Experiment 1, we offered 10 dogs' choices among alternative passages. The target passage led to more food than the competitor passage but required dogs to enter a narrower passage. The decoy passage asymmetrically dominated the competitor passage because although it contained a larger amount of food, it was narrower than the target passage. We found that dogs increased their preference for the target passage in the presence of the decoy passage, which violated the assumption of independence from irrelevant alternatives. Our second experiment controlled for energetic hunger state because previous findings had suggested that the violation effect might arise from changes in energetic state (Schuck-Paim et al., 2004). We provided supplementary feedings to each dog between each trial such that each dog consumed the same amount of food on each trial. The violation of independence from irrelevant alternatives effect persisted, though to a lesser degree than in Experiment 1. Cognitive implications are discussed.

Mental time travel: animals anticipate the future.

Recent behavioral experiments with scrub jays and nonhuman primates indicate they can anticipate and plan for future needs not currently experienced. Combined with accumulating evidence for episodic-like memory in animals, these studies suggest that some animals can mentally time travel into both the past and future.

The comparative study of mental time travel.

People regularly travel through time mentally to remember and reconstruct past events and to anticipate and plan future events. We suggest that a bi-cone structure best describes human mental time travel (MTT) abilities. Experiments with scrub-jays, rats and non-human primates have investigated whether MTT is uniquely human by examining the abilities of these animals to remember what, where and when an event occurred and to anticipate future events. We argue that animal memory for when an event happened must be distinguished from memory for how long ago it happened to properly evaluate parallels with human capabilities. Similarly, tests of future MTT in animals must show that they are planning for a specific time in the future to demonstrate qualitative comparability with human MTT.

A comparative study of memory for olfactory discriminations: Dogs (Canis familiaris), rats (Rattus norvegicus), and humans (Homo sapiens).

Disagreement has arisen in the scientific literature regarding the relative olfactory ability of humans relative to other mammals, specifically canines and rodents. A series of experiments are reported in which memory for multiple olfactory discriminations was measured in dogs, rats, and humans. Participants from all three species learned a sequence of 20 different discriminations between an S + odor and an S- odor. Choice of the S+ odor was rewarded with food for dogs and rats and with positive verbal feedback for humans. After learning the discriminations, an initial memory test was given that involved presentation of all 20 S + and S- pairs. A subsequent mix-and-match test was given in which each S + odor was presented with three different S- odors. The memory tests revealed that dogs were superior to rats and that dogs and rats were superior to humans. The relatively poor performance of humans contrasts with prior findings of high recognition memory for odors followed by slow forgetting. We attribute the low accuracy of humans in our experiments to the requirement that participants had to remember the outcome associated with S + (correct) and S- (incorrect) cues and not just their familiarity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

An isolation effect in rat spatial memory.

Rats' working memory for locations previously visited and not visited was tested on the radial maze. Trials consisted of a study phase followed by a test phase. In the study phase, rats were forced to visit half the arms on the maze, with the other half of the arms blocked. In the test phase, rats chose among all arms, with food found only on the arms not visited in the study phase. When different patterns of arms visited in the study phase were used, it was found that rats remembered an alternating pattern better than an adjacent pattern or a random pattern and that this effect became more pronounced at longer retention intervals. In addition, rats remembered isolated nonvisited arms in the random pattern that were sandwiched between visited arms better than nonvisited arms that were not isolated between visited arms. Several hypotheses were examined and tested to explain this isolation effect, but no clear theoretical account was found. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Information preferences across species: Pigeons, rats, and dogs.

We tested the information preferences of three different species; pigeons, rats and dogs. Eight animals of each species received forced trials that produced one of two stimulus sequences. In the first sequence, response to an initial stimulus led to one of two other stimuli, one of which guaranteed a food reward was coming and the other of which guaranteed no food reward was coming. In the second sequence, response to an initial stimulus led to one of two other stimuli, both of which predicted food reward on 50 % of the trials. The net reinforcement rate for both of the sequences was 50 %. On probe test trials, both initial stimuli were presented, and the subject chose between the informative and the non-informative cue, and the percent choice of the information sequence, in which stimuli predicted food or no food reliably, was recorded for each species across 10 sessions. Statistical tests showed that although pigeons showed a preference for the information sequence, neither rats nor dogs showed this preference. Experimental and ecological explanations are discussed.

Animal memory: episodic-like memory in rats.

Recent experiments with rats on a radial maze indicate that they can remember what foods they encountered, and when and where they encountered them. These findings, and others with food-storing birds, challenge the idea that only humans have episodic memory.