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.

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.

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.

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.

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.

Dogs (Canis familiaris) use odor cues to show episodic-like memory for what, where, and when.

Episodic-like memory is a personal memory that contains what happened, where it happened, and when it happened. Although episodic-like memory in nonhuman animals has been shown using what-where-when memory paradigms, it has not previously been shown in dogs. Dogs are an excellent candidate for developing translational models of neurodegenerative disorders related to episodic memory, including Alzheimer's disease. Dogs were tested in experiments that involved spatially and temporally unique sequences of odor stimuli to see if they remembered the odors, their locations, and their times of presentation. By choosing the earlier exposed odor on two-choice tests, dogs showed the ability to encode what-when, where-when, or what-where-when memory. Further tests revealed that dogs performed optimally when all three components of what-where-when memory were available for encoding and could flexibly use this information on unpredictable tests. Although the experiments reported here show that dogs remembered what, where, and when, they did not indicate whether these components were part of an integrated single memory or were retrieved from separate files. Evidence on the question of integrated memory requires trials on which all three components are tested. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Animal Cognition: Chimps Use Human Knowledge When Reasoning Statistically.

A recent study found that chimpanzees chose hidden rewards selected by humans from two populations containing different proportions of favoured and non-favoured items; their choice was based on statistical reasoning about random sampling, human preferences, and inferences about humans' knowledge of their own choices.

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.

Cognitive flexibility and dual processing in pigeons: Temporal and contextual control of midsession reversal.

Evidence is reported showing that pigeons flexibly use temporal and contextual cues to maximize reward obtained in a midsession reversal task. Pigeons were trained to choose between red and green sidekeys for 60 trials in a session, with choice of one color correct on Trials 1-30 and choice of the other color correct on Trials 31-60 (midsession reversal). Pigeons showed anticipatory errors before reversal and perseverative errors after reversal, and manipulations of the length of the intertrial interval and the point of reversal suggested that pigeons used an internal timer to track the point of reversal. When houselight context cues that signaled the correct choice were presented throughout trials in Experiment 1, choice behavior rapidly came under context control, leading pigeons to rarely make errors and to show no effect of intertrial interval or point of reversal. In Experiments 2 and 3, switches between context and no-context cues occurred among trials. These manipulations revealed that pigeons can readily switch between context control and temporal control of behavior. The internal timer continued to run throughout context trials and could readily be accessed to control choice behavior when a context cue was removed. (PsycINFO Database Record

On the clock: Interval timing and overshadowing in domestic dogs (Canis familiaris).

Interval timing is an important skill that allows animals to approximate how much time has elapsed since a given event. Little, however, is known about interval timing in domestic dogs. In an initial experiment, dogs were trained to make an operant response on 30-s fixed intervals, with either a light or a tone + light compound signaling the beginning of the fixed interval. When dogs in the compound group were subsequently tested with nonreinforced 60-s tone-only probe trials, the dogs' rate of responding peaked near 30 s. When the same dogs were tested with light-only probes, however, no evidence of timing was found. In a second experiment, a bisection task was used in which dogs had to learn to approach 1 feeder when given an 8-s tone + light signal, and another feeder when given a 2-s tone + light signal. When subsequently tested at intermediate durations, psychophysical curves showed clear control of timing by the tone stimulus but not by the light stimulus. These findings clearly demonstrate that dogs are able to time fixed intervals and show the existence of an overshadowing effect, in which dogs are able to time a light cue presented alone but do not attend to the light when it is presented simultaneously with a tone. (PsycINFO Database Record

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.

Episodic Memory: Rats Master Multiple Memories.

A new study in which rats had to discriminate odors according to whether they were novel for a particular environmental context has found that they can accurately discriminate a large number of odors and multiple context transitions, suggesting that they are able to form and remember multiple episodic memories.

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.

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.

Context controls access to working and reference memory in the pigeon (Columba livia).

The interaction between working and reference memory systems was examined under conditions in which salient contextual cues were presented during memory retrieval. Ambient colored lights (red or green) bathed the operant chamber during the presentation of comparison stimuli in delayed matching-to-sample training (working memory) and during the presentation of the comparison stimuli as S+ and S- cues in discrimination training (reference memory). Strong competition between memory systems appeared when the same contextual cue appeared during working and reference memory training. When different contextual cues were used, however, working memory was completely protected from reference memory interference.