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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 25, Issue 4, 2012

Research Paper

Spatial Cognition of Zebra Finches in a Morris-maze Analogue Apparatus

There are many studies of spatial memory in food-storing birds, but comparable studies in songbirds are rather rare. We have devised a Morris-maze analogue for zebra finches (Taeniopygia guttata). Here we examined the discriminative behavior of zebra finches ( N = 10) in the maze analogue used inprevious experiments. The birds, when released from different positions into the aviary, had to choose one baited feeder from four feeders. When the birds had learned this task, their performance in trials with a modified arrangement of the feeders was tested. Removal of a non-baited feeder did not disturb discrimination performance, while displacement of the position of the baited feeder (so asto move it closer to other feeders) disturbed discrimination. These results suggest that the bird sidentified the baited feeder by absolute position in reference to extra-maze cues, and that the non baited feeders affected the discriminative behavior by acting as distractors.

The Endowment Effect in Orangutans

The endowment effect is the tendency to, seemingly irrationally, immediately value a possessed item more than the opportunity to acquire the identical item when one does not already possess it. Although endowment effects are reported in chimpanzees (Brosnan, Jones, Lambeth, Mareno,Richardson, & Shapiro, 2007) and capuchin monkeys (Lakshminarayanan, Chen, & Santos, 2008), both species share social traits with humans that make convergence as likely an evolutionary mechanism as homology. Orangutans (Pongo spp.) provide a unique insight into the evolution of the endowment effect, along with other apparently irrational behaviors, because their less frequent socialinteractions and relatively more solitary social organization distinguishes them from the more gregarious apes, allowing a test of evolutionary homology. In the present study, we used pairs of both food and non-food objects, as in an earlier test on chimpanzees (Brosnan et al., 2007). We established the apes’ preferences in forced -choice tasks, then tested whether they showed an endowment effect inan exchange task, in which subjects were given one of the objects, followed by the option to exchange it for the other. Here, we report the first evidence of the endowment effect in a relatively less social primate, the orangutan. This indicates that this behavior may have evolved as a homology within the primates, rather than being due to convergent social pressures. These findings provide stronger evidence for the hypothesis that at least one bias, the endowment effect, may be common in primates and, potentially, other species.

Orangutans’ Use of Contiguous Versus Distal Social and Non-social Cues in an Object-choice Task

In this experiment, orangutans’ ability to use social versus non -social cues on an object-choice task was examined. In addition, the role of spatial proximity was investigated, by matching the distance between the cue and the target object across both social and non-social conditions. Subjects took significantly fewer trials to learn to use social cues (a finger touching the target object and an experimenter’s face hovering above the target object) than non -social cues (paper markers). There was no statistical difference between their performance with cues that were physically contiguous with the target object and those that were distal spatially, regardless of whether the cue was social ornon-social in nature. Evidence for spontaneous cue use was strongest for the social-contiguous condition (a finger touching the target object). These results suggest that spatial proximity alone cannot explain apes’ performance on these types of tasks. Although subjects may have difficulty deriving information from human-based gestures, they still appear to be more attuned to these cues than to abstract physical markers that are matched in terms of spatial relationship and reliability.

The Importance of Considering Context in the Assessment of Personality Characteristics: Evidence from Ratings of Dolphin Personality

One of the tenets of personality is that an individual’s distinguishing behavioral characteristics arerelatively stable over time and across contexts. Both humans and animals demonstrate suchconsistency, at least for certain personality traits. However, the relative extent to which personality isstable is rarely addressed in studies of animal personality, the focus typically being on stability ratherthan its absence. Here we present data on dolphin personality that suggest dolphin behavior (andhence their personality characteristics) is influenced by context, the three contexts of concern herebeing interactions with the physical environment, interactions with humans, and interactions withother dolphins. Individuals differed in terms of the extent to which their behavior was ratedconsistently across the three contexts, suggesting that an important aspect of personality concerns therole of context in moderating individual predispositions.