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.

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.

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.

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.

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.

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.