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Kelly, D. M., & Spetch, M. L. (2001). Pigeons encode relative geometry. J Exp Psychol Anim Behav Process, 27(4), 417–422.
Abstract: Pigeons were trained to search for hidden food in a rectangular environment designed to eliminate any external cues. Following training, the authors administered unreinforced test trials in which the geometric properties of the apparatus were manipulated. During tests that preserved the relative geometry but altered the absolute geometry of the environment, the pigeons continued to choose the geometrically correct corners, indicating that they encoded the relative geometry of the enclosure. When tested in a square enclosure, which distorted both the absolute and relative geometry, the pigeons randomly chose among the 4 corners, indicating that their choices were not based on cues external to the apparatus. This study provides new insight into how metric properties of an environment are encoded by pigeons.
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Nakamura, K. (2001). Perseverative errors in object discrimination learning by aged Japanese monkeys (Macaca fuscata). J Exp Psychol Anim Behav Process, 27(4), 345–353.
Abstract: To examine the nature of age-dependent cognitive decline, performance in terms of concurrent object discriminations was assessed in aged and nonaged Japanese monkeys (Macaca fuscata). Aged monkeys required more sessions and committed more errors than nonaged ones in the discriminations, even in simple object discriminations. Analyses of errors suggest that aged monkeys repeated the same errors and committed more errors when they chose a negative object at the 1st trial. A hypothesis analysis of behavior suggests that their incorrect choices were mainly due to object preference. Therefore, the impairment was probably caused by a failure to inhibit inappropriate responses. Together with previous neuropsychological findings, deficits of aged monkeys in the performance of object discriminations can be explained by dysfunction of the frontal cortex.
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Fagot, J., Wasserman, E. A., & Young, M. E. (2001). Discriminating the relation between relations: the role of entropy in abstract conceptualization by baboons (Papio papio) and humans (Homo sapiens). J Exp Psychol Anim Behav Process, 27(4), 316–328.
Abstract: Two baboons (Papio papio) successfully learned relational matching-to-sample: They picked the choice display that involved the same relation among 16 pictures (same or different) as the sample display, although the sample display shared no pictures with the choice displays. The baboons generalized relational matching behavior to sample displays created from novel pictures. Further experiments varying the number of sample pictures and the mixture of same and different sample pictures suggested that entropy plays a key role in the baboons' conceptual behavior. Two humans (Homo sapiens) were similarly trained and tested; their behavior was both similar to and different from the baboons' behavior. The results suggest that animals other than humans and chimpanzees can discriminate the relation between relations. They further suggest that entropy detection may underlie same-different conceptualization, but that additional processes may participate in human conceptualization.
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Crystal, J. D. (1999). Systematic nonlinearities in the perception of temporal intervals. J Exp Psychol Anim Behav Process, 25(1), 3–17.
Abstract: Rats judged time intervals in a choice procedure in which accuracy was maintained at approximately 75% correct. Sensitivity to time (d') was approximately constant for short durations 2.0-32.0 s with 1.0- or 2.0-s spacing between intervals (n = 5 in each group, Experiment 1), 2.0-50.0 s with 2.0-s spacing (n = 2, Experiment 1), and 0.1-2.0 s with 0.1- or 0.2-s spacing (n = 6 in each group, Experiment 2). However, systematic departures from average sensitivity were observed, with local maxima in sensitivity at approximately 0.3, 1.2, 10.0, 24.0, and 36.0 s. Such systematic departures from an approximately constant d' are predicted by a connectionist theory of time with multiple oscillators and may require a modification of the linear timing hypothesis of scalar timing theory.
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Boysen, S. T., Bernston, G. G., Hannan, M. B., & Cacioppo, J. T. (1996). Quantity-based interference and symbolic representations in chimpanzees (Pan troglodytes). J Exp Psychol Anim Behav Process, 22(1), 76–86.
Abstract: Five chimpanzees with training in counting and numerical skills selected between 2 arrays of different amounts of candy or 2 Arabic numerals. A reversed reinforcement contingency was in effect, in which the selected array was removed and the subject received the nonselected candies (or the number of candies represented by the nonselected Arabic numeral). Animals were unable to maximize reward by selecting the smaller array when candies were used as array elements. When Arabic numerals were substituted for the candy arrays, all animals showed an immediate shift to a more optimal response strategy of selecting the smaller numeral, thereby receiving the larger reward. Results suggest that a response disposition to the high-incentive candy stimuli introduced a powerful interference effect on performance, which was effectively overridden by the use of symbolic representations.
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Parr, L. A., Winslow, J. T., Hopkins, W. D., & de Waal, F. B. (2000). Recognizing facial cues: individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). J Comp Psychol, 114(1), 47–60.
Abstract: Faces are one of the most salient classes of stimuli involved in social communication. Three experiments compared face-recognition abilities in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). In the face-matching task, the chimpanzees matched identical photographs of conspecifics' faces on Trial 1, and the rhesus monkeys did the same after 4 generalization trials. In the individual-recognition task, the chimpanzees matched 2 different photographs of the same individual after 2 trials, and the rhesus monkeys generalized in fewer than 6 trials. The feature-masking task showed that the eyes were the most important cue for individual recognition. Thus, chimpanzees and rhesus monkeys are able to use facial cues to discriminate unfamiliar conspecifics. Although the rhesus monkeys required many trials to learn the tasks, this is not evidence that faces are not as important social stimuli for them as for the chimpanzees.
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Dorrance, B. R., & Zentall, T. R. (2002). Imitation of conditional discriminations in pigeons (Columba livia). J Comp Psychol, 116(3), 277–285.
Abstract: In the present experiments, the 2-action method was used to determine whether pigeons could learn to imitate a conditional discrimination. Demonstrator pigeons (Columba livia) stepped on a treadle in the presence of 1 light and pecked at the treadle in the presence of another light. Demonstration did not seem to affect acquisition of the conditional discrimination (Experiment 1) but did facilitate its reversal of the conditional discrimination (Experiments 2 and 3). The results suggest that pigeons are not only able to learn a specific behavior by observing another pigeon, but they can also learn under which circumstances to perform that behavior. The results have implications for proposed mechanisms of imitation in animals.
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Sutton, J. E., & Shettleworth, S. J. (2005). Internal sense of direction and landmark use in pigeons (Columba livia). J Comp Psychol, 119(3), 273–284.
Abstract: The relative importance of an internal sense of direction based on inertial cues and landmark piloting for small-scale navigation by White King pigeons (Columba livia) was investigated in an arena search task. Two groups of pigeons differed in whether they had access to visual cues outside the arena. In Experiment 1, pigeons were given experience with 2 different entrances and all pigeons transferred accurate searching to novel entrances. Explicit disorientation before entering did not affect accuracy. In Experiments 2-4, landmarks and inertial cues were put in conflict or tested 1 at a time. Pigeons tended to follow the landmarks in a conflict situation but could use an internal sense of direction to search when landmarks were unavailable.
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Stoinski, T. S., Wrate, J. L., Ure, N., & Whiten, A. (2001). Imitative learning by captive western lowland gorillas (Gorilla gorilla gorilla) in a simulated food-processing task. J Comp Psychol, 115(3), 272–281.
Abstract: Although field studies have suggested the existence of cultural transmission of foraging techniques in primates, identification of transmission mechanisms has remained elusive. To test experimentally for evidence of imitation in the current study, we exposed gorillas (Gorilla gorilla gorilla) to an artificial fruit foraging task designed by A. Whiten and D. M. Custance (1996). Gorillas (n=6) watched a human model remove a series of 3 defenses around a fruit. Each of the defenses was removed using 1 of 2 alternative techniques. Subsequent video analysis of gorillas' behavior showed a significant tendency to copy the observed technique on 1 of the individual defenses and the direction of removal on another defense. This is the first statistically reliable evidence of imitation in gorillas. Sequence of defense removal was not replicated. The gorillas' responses were most similar to those of chimpanzees.
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Whiten, A., Custance, D. M., Gomez, J. C., Teixidor, P., & Bard, K. A. (1996). Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes). J Comp Psychol, 110(1), 3–14.
Abstract: Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2-4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild.
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