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.

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.

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.

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.

Memory systems interaction in the pigeon: working and reference memory.

Pigeons' performance on a working memory task, symbolic delayed matching-to-sample, was used to examine the interaction between working memory and reference memory. Reference memory was established by training pigeons to discriminate between the comparison cues used in delayed matching as S+ and S- stimuli. Delayed matching retention tests then measured accuracy when working and reference memory were congruent and incongruent. In 4 experiments, it was shown that the interaction between working and reference memory is reciprocal: Strengthening either type of memory leads to a decrease in the influence of the other type of memory. A process dissociation procedure analysis of the data from Experiment 4 showed independence of working and reference memory, and a model of working memory and reference memory interaction was shown to predict the findings reported in the 4 experiments. (PsycINFO Database Record

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.

Dogs choose a human informant: metacognition in canines.

The presence of metacognition in animals has been suggested by the observation that non-human primates will seek out information about the location of a hidden reward before responding. In experiment 1, dogs failed to make an information-seeking response that involved re-positioning themselves in space so that they could view a cue that indicated the location of food. In experiments 2 and 3, dogs were allowed to choose between two people, an informant that pointed to the location of food and a non-informant that provided no information. Dogs showed a clear preference for the informant, even when choice of the informant led to no greater chance of reward than choice of the non-informant. In a procedure that involves human communication, dogs show information-seeking behavior.

Spatial memory in dogs (Canis familiaris) on a radial maze.

Working spatial memory in dogs (Canis familiaris) was tested in Experiments 1 and 2 on an 8-arm radial maze. When dogs chose freely among all 8 arms containing food in Experiment 1, they learned to enter all 8 arms with progressively fewer arm visits over trials. In Experiment 2, 2 groups of dogs were forced to visit 4 randomly chosen arms on the maze and then tested for memory of these arm visits using a win-shift rule for 1 group and a win-stay rule for the other group. Dogs performed better with the win-shift rule than with the win-stay rule. In Experiment 3, reference memory was investigated by using a 4-arm maze on which 0, 1, 3, and 6 pieces of food were consistently placed on different arms. Dogs learned to visit the arms with the larger amounts before the arms with the smaller amounts. Dogs' memory capacity in these studies was found to be surprisingly low.

Do pigeons (Columba livia) study for a test?

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.

Episodic-like memory in rats: is it based on when or how long ago?

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.

Do dogs (Canis familiaris) seek help in an emergency?

The question of whether dogs recognize an emergency and understand the need to seek help from a bystander was tested in two experiments. In the first experiment, dogs' owners feigned a heart attack in an open field, and in the second experiment, dogs' owners experienced an accident in which a bookcase fell on them and pinned them to the floor. In these experiments, one or two bystanders were available to which dogs could go for help. The dogs' behavior was taped for 6 min after the owner had fallen and was later scored for the frequency and time the dogs spent performing different behaviors. In no case did a dog solicit help from a bystander. It is concluded that dogs did not understand the nature of the emergency or the need to obtain help.