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.