Abstract: During the pre-maturation period crowded males of Schistocerca gregaria are more active than isolated ones but the greater part of their extra activity is not locomotory but consists of the kicking movements made in response to contact with other locusts. Isolated males walk less often during this period but tend to jump (or fly) more than crowded ones. Activity increases with maturity and the increase is greater in the isolated males so that in spite of the absence of mechanical stimulation by other locusts their locomotor activity is now at least as great as that of the crowded ones and their jumping activity greater. Within one batch there is a tendency for those males which are most active during the first two weeks of adult life to mature earliest. The activity of young males crowded with fledglings is at first similar to that of males crowded with older locusts, but after the first two weeks the activity of both mature and immature males is depressed by crowding with fledglings. Mature males habitually isolated become less active when temporarily crowded with fledglings, but not when crowded with mature males. Mature and immature males habitually crowded with fledglings become more active when temporarily isolated and still more active when crowded with each other, or with other mature males. The inhibiting effect of the fledglings on maturation and their depressive effect on activity should in natural conditions promote synchronization of maturation and the cohesion of the group. There was little difference in activity between young males kept in single pairs and in isolation, except that in one experiment the isolated ones jumped more often. Young males kept in pairs with mature males are more active during the first week of adult life than those kept in pairs with each other. The males paired with mature males were also seen feeding much less often than those paired with each other. This was the only treatment in which a significant effect on the frequency of feeding was recorded. The femoral vibrations made by both mature and immature males in response to stimulation by mature males, occur less often in habitually crowded males than in those temporarily crowded or kept with one mature male only. This is presumably the result of habituation to the stimulus. The behaviour of wild Schistocerca males in a large outdoor cage was very similar to that of a low density laboratory group. All results suggest that there is an association between high activity and rapid maturation. This is compatible with the conclusion from earlier work that a low level of feeding is associated with rapid maturation.

Abstract: Chimpanzees, Pan troglodytes, produce numerous species-atypical signals when raised in captivity. We examined contextual elements of the use of two of these vocal signals, the `raspberry' and the extended grunt. Our results demonstrate that these vocalizations are not elicited by the presence of food, but instead function as attention-getting signals. These findings reveal a heretofore underappreciated category of animal signals: attention-getting sounds produced in novel environmental circumstances. The invention and use of species-atypical signals, considered in relation to group differences in signalling repertoires in apes in their natural habitats, may index a generative capacity in these hominoid species without obvious corollary in other primate species.

Abstract: An important aspect of cognition is whether animals live exclusively in the present or can anticipate the future. Defined as self-control, the ability to choose a large, remote reinforcer over a small, proximate reinforcer available at the same frequency has been examined in a number of species, often proving difficult to demonstrate. We investigated self-control for food in domestic fowl using a standard two-key operant task and an equivalent two-choice return maze (TCRM) task. When hens chose between a 2-s delay to a 3-s feed access (impulsive) and a 6-s delay to a 7-s feed access (self-control), they appeared unable to discriminate in the TCRM but were impulsive in the operant task. We explored reasons for not choosing self-control in the operant task, first by examining the relation between feed access time and actual feed intake. A second operant experiment examined whether failure to show self-control could be attributed to an inability to combine the delay and access (quantity) reward information associated with choices to reach overall predictions of value. New hens chose between a 2-s delay to a 3-s feed access (impulsive) and either a 22-s delay to a 22-s feed access (standard self-control) or a 6-s delay to a 22-s feed access (jackpot self-control). While hens were impulsive in the standard condition, they showed significant and pronounced self-control in the jackpot condition, eliminating the possibility of an absolute cognitive constraint. Impulsive behaviour can instead be explained by temporal discounting: perceived depreciation of reward value as a function of the uncertainty associated with delay. Implications for welfare are discussed.

Abstract: Traditionally, dogs have been trained by operant conditioning techniques; that is, dogs make a desired behavioural response and this response is reinforced by a reward such as food. This type of training is very effective in training dogs to perform basic obedience behaviours (e.g. `stay'). However, dogs are social animals and should be predisposed to learn from social stimuli. In the present study, we used a modified version of the model-rival technique that has been extensively used in experiments investigating the cognitive ability of parrots. In this technique, social stimuli are used to create in the animal an interest in the object without the use of food or other rewards. Therefore, the animal learns the name of the object (intrinsic reward) and not that the object's name means food. In this experiment we compared the learning ability of nine pet dogs to solve the same retrieval-selection task having been previously trained using operant conditioning or model-rival techniques. The retrieval-selection task was the dogs had to correctly select the commanded object to bring to the experimenter from a group of three similar objects. The results show no difference in the speeds with which the dogs solved the test--demonstrating the efficacy of the model-rival method. This is the first time that the effectiveness of the model-rival technique has been experimentally demonstrated with dogs. Furthermore, we believe that the methodology reported in this paper has applications in dog training and in experiments into dog cognition.