Abstract: Rats collected nuts from a container in a large arena in four experiments testing how learning about a beacon or cue at a goal interacts with learning about other spatial cues (place learning). Place learning was quick, with little evidence of competition from the beacon (Experiments 1 and 2). Rats trained to approach a beacon regardless of its location were subsequently impaired when the well-learned beacon was removed and other spatial cues identified the location of the goal (Experiment 3). The competition between beacon and place cues reflected learned irrelevance for place cues (Experiment 4). The findings differ from those of some studies of associative interactions between cue and place learning in other paradigms.

Abstract: We report the results of a 4-year-long study of capuchin monkeys ( Cebus apella ) on concurrent three-way classification and linear size seriation tasks using explicit ordering procedures, requiring subjects to select icons displayed on touch screens rather than manipulate and sort actual objects into groups. The results indicate that C. apella is competent to classify nine items concurrently, first into three disjoint classes where class exemplars are identical to one another, then into three reciprocal classes which share common exemplar (size) features. In the final phase we compare the relative efficiency of executive control under conditions where both hierarchical and/or linear organization can be utilized. Whilst this shows a superiority of categorical based size seriation for a nine item test set suggesting an adaptive advantage for hierarchical over linear organization, Cebus nevertheless achieved high levels of principled linear size seriation with sequence lengths not normally achieved by children below the age of six years.

Abstract: Six horses (Equus caballus) were trained to discriminate color from grays in a counterbalanced sequence in which lightness cues were irrelevant. Subsequently, the pretrained colors were presented in a different sequence. Two sets of novel colors paired with novel grays were also tested. Performance was just as good in these transfer tests. Once the horse had learned to select the chromatic from the achromatic stimulus, regardless of the specific color, they were immediately able to apply this rule to novel stimuli. In terms of the underlying visual mechanisms, the present study showed for the first time that the spectral sensitivity of horse cone photopigments, measured as cone excitation ratios, was correlated with color discrimination performance, measured as accuracy, repeated errors, and latency of approach.

Abstract: When humans are asked to evaluate rewards or outcomes that follow unpleasant (e.g., high-effort) events, they often assign higher value to that reward. This phenomenon has been referred to as cognitive dissonance or justification of effort. There is now evidence that a similar phenomenon can be found in nonhuman animals. When demonstrated in animals, however, it has been attributed to contrast between the unpleasant high effort and the conditioned stimulus for food. In the present experiment, we asked whether an analogous effect could be found in humans under conditions similar to those found in animals. Adult humans were trained to discriminate between shapes that followed a high-effort versus a low-effort response. In test, participants were found to prefer shapes that followed the high-effort response in training. These results suggest the possibility that contrast effects of the sort extensively studied in animals may play a role in cognitive dissonance and other related phenomena in humans.

Abstract: After Charles Darwin's The Expression of the Emotions in Man and Animals, published in 1872, we had to wait 60 years before the theme of animal expressions was picked up by another astute observer. In 1935, Nadezhda Ladygina-Kohts published a detailed comparison of the expressive behavior of a juvenile chimpanzee and of her own child. After Kohts, we had to wait until the 1960s for modern ethological analyses of primate facial and gestural communication. Again, the focus was on the chimpanzee, but ethograms on other primates appeared as well. Our understanding of the range of expressions in other primates is at present far more advanced than that in Darwin's time. A strong social component has been added: instead of focusing on the expressions per se, they are now often classified according to the social situations in which they typically occur. Initially, quantitative analyses were sequential (i.e., concerned with temporal associations between behavior patterns), and they avoided the language of emotions. I will discuss some of this early work, including my own on the communicative repertoire of the bonobo, a close relative of the chimpanzee (and ourselves). I will provide concrete examples to make the point that there is a much richer matrix of contexts possible than the common behavioral categories of aggression, sex, fear, play, and so on. Primate signaling is a form of negotiation, and previous classifications have ignored the specifics of what animals try to achieve with their exchanges. There is also increasing evidence for signal conventionalization in primates, especially the apes, in both captivity and the field. This process results in group-specific or “cultural” communication patterns.