Animal behaviour: cognitive bias and affective state.

Information processing by humans can be biased by their emotions — for example, anxious and depressed people tend to make negative judgements about events and to interpret ambiguous stimuli unfavourably1, 2, 3, 4. Here we show that such a ‘pessimistic’ response bias can also be measured in rats that are housed in unpredictable conditions5, 6. […]

Immobility and supination in garter snakes (Thamnophis elegans) following handling by human predators

A common response of animals to physical restraint is tonic immobility. The authors observed the behavior of garter snakes, Thamnophis elegans, in the field to determine the frequency of immobility as a response to handling. Most snakes fled after release, but the remainder remained immobile, sometimes on their backs (supination), for up to 10 min. […]

Referential Communication by Chimpanzees (Pan troglodytes)

Two experiments were conducted to assess the referential function of chimpanzee (Pan troglodytes) gestures to obtain food. The chimpanzees received 1 trial per condition. In Experiment 1 (N 101), in full view of the chimpanzee, a banana was placed on top of 1 of 2 inverted buckets or was hidden underneath 1 of the buckets. […]

Comparative behavior of primates. II. Delayed reaction tests on primates at Bronx

Tests were carried out on 18 primates, using the direct method involved in the authors’ previous studies. The results showed “increased capacity in order from the lemur, platyrrhine monkeys, catarrhine monkeys to the baboons. Attention is especially called to the clear superiority of the latter, since they have often been thought inferior. There was found […]

An experimental study of duet integration in the happy wren, Pheugopedius felix

Pairs of duetting birds can sing coordinated duets with such precision that they are often mistaken for a single individual, yet little is known about how this impressive temporal synchronization is achieved. We experimentally examined duet coordination in male happy wrens, held briefly in captivity, by playing song phrases from their partner at different distances […]