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Evans, T. A., & Westergaard, G. C. (2004). Discrimination of functionally appropriate and inappropriate throwing tools by captive tufted capuchins (Cebus apella). Anim. Cogn., 7(4), 255–262.
Abstract: A tool-throwing task was used to test whether capuchin monkeys understand the difference between functionally appropriate and functionally inappropriate tools. A group of monkeys was trained to obtain a sticky treat from a container outside their enclosure using a projectile attached to one end of an anchored line. Subsequently, these monkeys were given choice tests between functional and nonfunctional versions of tools used in training. A different feature of the tool was varied between alternatives in each choice test. The monkeys chose to use functional tools significantly more often than nonfunctional tools in early exposures to each choice test. A second experiment tested whether these subjects, as well as a second group of minimally trained participants, could distinguish between functional and nonfunctional tools that appeared different from those used in training. A new set of design features was varied between tools in these choice tests. All participants continued to choose functional tools significantly more often than nonfunctional tools, regardless of their tool-throwing experience or the novel appearance of the tools. These results suggest that capuchin monkeys, like chimpanzees studied in similar experiments, are sensitive to a variety of functionally relevant tool features.
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Hampton, R. R., Zivin, A., & Murray, E. A. (2004). Rhesus monkeys (Macaca mulatta) discriminate between knowing and not knowing and collect information as needed before acting. Anim. Cogn., 7(4), 239–246.
Abstract: Humans use memory awareness to determine whether relevant knowledge is available before acting, as when we determine whether we know a phone number before dialing. Such metacognition, or thinking about thinking, can improve selection of appropriate behavior. We investigated whether rhesus monkeys ( Macaca mulatta) are capable of a simple form of metacognitive access to the contents of short-term memory. Monkeys chose among four opaque tubes, one of which concealed food. The tube containing the reward varied randomly from trial to trial. On half the trials the monkeys observed the experimenter baiting the tube, whereas on the remaining trials their view of the baiting was blocked. On each trial, monkeys were allowed a single chance to select the tube containing the reward. During the choice period the monkeys had the opportunity to look down the length of each tube, to determine if it contained food. When they knew the location of the reward, most monkeys chose without looking. In contrast, when ignorant, monkeys often made the effort required to look, thereby learning the location of the reward before choosing. Looking improved accuracy on trials on which monkeys had not observed the baiting. The difference in looking behavior between trials on which the monkeys knew, and trials on which they were ignorant, suggests that rhesus monkeys discriminate between knowing and not knowing. This result extends similar observations made of children and apes to a species of Old World monkey, suggesting that the underlying cognitive capacities may be widely distributed among primates.
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Kaminski, J., Call, J., & Tomasello, M. (2004). Body orientation and face orientation: two factors controlling apes' behavior from humans. Anim. Cogn., 7(4), 216–223.
Abstract: A number of animal species have evolved the cognitive ability to detect when they are being watched by other individuals. Precisely what kind of information they use to make this determination is unknown. There is particular controversy in the case of the great apes because different studies report conflicting results. In experiment 1, we presented chimpanzees, orangutans, and bonobos with a situation in which they had to request food from a human observer who was in one of various attentional states. She either stared at the ape, faced the ape with her eyes closed, sat with her back towards the ape, or left the room. In experiment 2, we systematically crossed the observer's body and face orientation so that the observer could have her body and/or face oriented either towards or away from the subject. Results indicated that apes produced more behaviors when they were being watched. They did this not only on the basis of whether they could see the experimenter as a whole, but they were sensitive to her body and face orientation separately. These results suggest that body and face orientation encode two different types of information. Whereas face orientation encodes the observer's perceptual access, body orientation encodes the observer's disposition to transfer food. In contrast to the results on body and face orientation, only two of the tested subjects responded to the state of the observer's eyes.
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Cleveland, A., Rocca, A. M., Wendt, E. L., & Westergaard, G. C. (2004). Transport of tools to food sites in tufted capuchin monkeys (Cebus apella). Anim. Cogn., 7(3), 193–198.
Abstract: Tool use and transport represent cognitively important aspects of early hominid evolution, and nonhuman primates are often used as models to examine the cognitive, ecological, morphological and social correlates of these behaviors in order to gain insights into the behavior of our early human ancestors. In 2001, Jalles-Filho et al. found that free-ranging capuchin monkeys failed to transport tools (stones) to food sites (nuts), but transported the foods to the tool sites. This result cast doubt on the usefulness of Cebus to model early human tool-using behavior. In this study, we examined the performance of six captive tufted capuchin monkeys (Cebus apella) in a tool transport task. Subjects were provided with the opportunity to transport two different tools to fixed food reward sites when the food reward was visible from the tool site and when the food reward was not visible from the tool site. We found that the subjects quickly and readily transported probing tools to an apparatus baited with syrup, but rarely transported stones to a nut-cracking apparatus. We suggest that the performance of the capuchins here reflects an efficient foraging strategy, in terms of energy return, among wild Cebus monkeys.
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Katz, J. S., & Wright, A. A. (2006). Same/different abstract-concept learning by pigeons. J Exp Psychol Anim Behav Process, 32(1), 80–86.
Abstract: Eight pigeons were trained and tested in a simultaneous same/different task. After pecking an upper picture, they pecked a lower picture to indicate same or a white rectangle to indicate different. Increases in the training set size from 8 to 1,024 items produced improved transfer from 51.3% to 84.6%. This is the first evidence that pigeons can perform a two-item same/different task as accurately with novel items as training items and both above 80% correct. Fixed-set control groups ruled out training time or transfer testing as producing the high level of abstract-concept learning. Comparisons with similar experiments with rhesus and capuchin monkeys showed that the ability to learn the same/different abstract concept was similar but that pigeons require more training exemplars.
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Murai, C., Tomonaga, M., Kamegai, K., Terazawa, N., & Yamaguchi, M. K. (2004). Do infant Japanese macaques ( Macaca fuscata) categorize objects without specific training? Primates, 45(1), 1–6.
Abstract: In the present study, we examined whether infant Japanese macaques categorize objects without any training, using a similar technique also used with human infants (the paired-preference method). During the familiarization phase, subjects were presented twice with two pairs of different objects from one global-level category. During the test phase, they were presented twice with a pair consisting of a novel familiar-category object and a novel global-level category object. The subjects were tested with three global-level categories (animal, furniture, and vehicle). It was found that they showed significant novelty preferences as a whole, indicating that they processed similarities between familiarization objects and novel familiar-category objects. These results suggest that subjects responded distinctively to objects without training, indicating the possibility that infant macaques possess the capacity for categorization.
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Rilling, M. E., & Neiworth, J. J. (1991). How animals use images. Sci Prog, 75(298 Pt 3-4), 439–452.
Abstract: Animal cognition is a field within experimental psychology in which cognitive processes formerly studied exclusively with people have been demonstrated in animals. Evidence for imagery in the pigeon emerges from the experiments described here. The pigeon's task was to discriminate, by pecking the appropriate choice key, between a clock hand presented on a video screen that rotated clockwise with constant velocity from a clock hand that violated constant velocity. Imagery was defined by trials on which the line rotated from 12.00 o'clock to 3.00 o'clock, then disappeared during a delay, and reappeared at a final stop location beyond 3.00 o'clock. After acquisition of a discrimination with final stop locations at 3.00 o'clock and 6.00 o'clock, the evidence for imagery was the accurate responding of the pigeons to novel locations at 4.00 o'clock and 7.00 o'clock. Pigeons display evidence of imagery by transforming a representation of movement that includes a series of intermediate steps which accurately represent the location of a moving stimulus after it disappears.
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Paukner, A., Anderson, J. R., & Fujita, K. (2006). Redundant food searches by capuchin monkeys (Cebus apella): a failure of metacognition? Anim. Cogn., 9(2), 110–117.
Abstract: This study investigated capuchin monkeys' understanding of their own visual search behavior as a means to gather information. Five monkeys were presented with three tubes that could be visually searched to determine the location of a bait. The bait's visibility was experimentally manipulated, and the monkeys' spontaneous visual searches before tube selection were analyzed. In Experiment 1, three monkeys selected the baited tube significantly above chance; however, the monkeys also searched transparent tubes. In Experiment 2, a bent tube in which food was never visible was introduced. When the bent tube was baited, the monkeys failed to deduce the bait location and responded randomly. They also continued to look into the bent tube despite not gaining any pertinent information from it. The capuchin monkeys' behavior contrasts with the efficient employment of visual search behavior reported in humans, apes and macaques. This difference is consistent with species-related variations in metacognitive abilities, although other explanations are also possible.
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Moses, S. N., Villate, C., & Ryan, J. D. (2006). An investigation of learning strategy supporting transitive inference performance in humans compared to other species. Neuropsychologia, 44(8), 1370–1387.
Abstract: Generalizations about neural function are often drawn from non-human animal models to human cognition, however, the assumption of cross-species conservation may sometimes be invalid. Humans may use different strategies mediated by alternative structures, or similar structures may operate differently within the context of the human brain. The transitive inference problem, considered a hallmark of logical reasoning, can be solved by non-human species via associative learning rather than logic. We tested whether humans use similar strategies to other species for transitive inference. Results are crucial for evaluating the validity of widely accepted assumptions of similar neural substrates underlying performance in humans and other animals. Here we show that successful transitive inference in humans is unrelated to use of associative learning strategies and is associated with ability to report the hierarchical relationship among stimuli. Our work stipulates that cross-species generalizations must be interpreted cautiously, since performance on the same task may be mediated by different strategies and/or neural systems.
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Call, J., Brauer, J., Kaminski, J., & Tomasello, M. (2003). Domestic dogs (Canis familiaris) are sensitive to the attentional state of humans. J Comp Psychol, 117(3), 257–263.
Abstract: Twelve domestic dogs (Canis familiaris) were given a series of trials in which they were forbidden to take a piece of visible food. In some trials, the human continued to look at the dog throughout the trial (control condition), whereas in others, the human (a) left the room, (b) turned her back, (c) engaged in a distracting activity, or (d) closed her eyes. Dogs behaved in clearly different ways in most of the conditions in which the human did not watch them compared with the control condition, in which she did. In particular, when the human looked at them, dogs retrieved less food, approached it in a more indirect way, and sat (as opposed to laid down) more often than in the other conditions. Results are discussed in terms of domestic dogs' social-cognitive skills and their unique evolutionary and ontogenetic histories.
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