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Bard, K. A. (2007). Neonatal imitation in chimpanzees (Pan troglodytes) tested with two paradigms. Anim. Cogn., 10(2), 233–242.
Abstract: Primate species differ in their imitative performance, perhaps reflecting differences in imitative capacity. The developmentally earliest form of imitation in humans, neonatal imitation, occurs in early interactions with social partners, and may be a more accurate index of innate capacity than imitation of actions on objects, which requires more cognitive ability. This study assessed imitative capacity in five neonatal chimpanzees, within a narrow age range (7-15 days of age), by testing responses to facial and vocal actions with two different test paradigms (structured and communicative). Imitation of mouth opening was found in both paradigms. In the communicative paradigm, significant agreement was found between infant actions and demonstrations. Additionally, chimpanzees matched the sequence of three actions of the TC model, but only on the second demonstration. Newborn chimpanzees matched more modeled actions in the communicative test than in the structured paradigm. These performances of chimpanzees, at birth, are in agreement with the literature, supporting a conclusion that imitative capacity is not unique to the human species. Developmental histories must be more fully considered in the cross-species study of imitation, as there is a greater degree of innate imitative capacity than previously known. Socialization practices interact with innate and developing competencies to determine the outcome of imitation tests later in life.
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Herrmann, E., Melis, A. P., & Tomasello, M. (2006). Apes' use of iconic cues in the object-choice task. Anim. Cogn., 9(2), 118–130.
Abstract: In previous studies great apes have shown little ability to locate hidden food using a physical marker placed by a human directly on the target location. In this study, we hypothesized that the perceptual similarity between an iconic cue and the hidden reward (baited container) would help apes to infer the location of the food. In the first two experiments, we found that if an iconic cue is given in addition to a spatial/indexical cue – e.g., picture or replica of a banana placed on the target location – apes (chimpanzees, bonobos, orangutans, gorillas) as a group performed above chance. However, we also found in two further experiments that when iconic cues were given on their own without spatial/indexical information (iconic cue held up by human with no diagnostic spatial/indexical information), the apes were back to chance performance. Our overall conclusion is that although iconic information helps apes in the process of searching hidden food, the poor performance found in the last two experiments is due to apes' lack of understanding of the informative (cooperative) communicative intention of the experimenter.
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Uller, C. (2004). Disposition to recognize goals in infant chimpanzees. Anim. Cogn., 7(3), 154–161.
Abstract: Do nonhuman primates attribute goals to others? Traditional studies with chimpanzees provide equivocal evidence for “mind reading” in nonhuman primates. Here we adopt looking time, a methodology commonly used with human infants to test infant chimpanzees. In this experiment, four infant chimpanzees saw computer-generated stimuli that mimicked a goal-directed behavior. The baby chimps performed as well as human infants, namely, they were sensitive to the trajectories of the objects, thus suggesting that chimpanzees may be endowed with a disposition to understand goal-directed behaviors. The theoretical implications of these results are discussed.
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Hunt, G. R., Rutledge, R. B., & Gray, R. D. (2006). The right tool for the job: what strategies do wild New Caledonian crows use? Anim. Cogn., 9(4), 307–316.
Abstract: New Caledonian crows Corvus moneduloides (NC crows) display sophisticated tool manufacture in the wild, but the cognitive strategy underlying these skills is poorly understood. Here, we investigate what strategy two free-living NC crows used in response to a tool-length task. The crows manufactured tools to extract food from vertical holes of different depths. The first tools they made in visits were of a similar length regardless of the hole depth. The typical length was usually too short to extract food from the deep holes, which ruled out a strategy of immediate causal inference on the first attempt in a trial. When the first tool failed, the crows made second tools significantly longer than the unsuccessful first tools. There was no evidence that the crows made the lengths of first tools to directly match hole depth. We argue that NC crows may generally use a two-stage heuristic strategy to solve tool problems and that performance on the first attempt in a trial is not necessarily the 'gold standard' for assessing folk physics.
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Dunbar, R. I. M., McAdam, M. R., & O'connell, S. (2005). Mental rehearsal in great apes (Pan troglodytes and Pongo pygmaeus) and children. Behav. Process., 69(3), 323–330.
Abstract: The ability to rehearse possible future courses of action in the mind is an important feature of advanced social cognition in humans, and the “social brain” hypothesis implies that it might also be a feature of primate social cognition. We tested two chimpanzees, six orangutans and 63 children aged 3-7 years on a set of four puzzle boxes, half of which were presented with an opportunity to observe the box before being allowed to open it (“prior view”), the others being given without an opportunity to examine the boxes before handling them (“no prior view”). When learning effects are partialled out, puzzle boxes in the “prior view” condition were opened significantly faster than boxes given in the “no prior view” condition by the children, but not by either of the great apes. The three species differ significantly in the speed with which they opened boxes in the “no prior view” condition. The three species' performance on this task was a function of relative frontal lobe volume, suggesting that it may be possible to identify quantitative neuropsychological differences between species.
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Cattell, R. B., & Korth, B. (1973). The isolation of temperament dimensions in dogs. Behav Biol, 9(1), 15–30.
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Call, J. (2006). Inferences by exclusion in the great apes: the effect of age and species. Anim. Cogn., 9(4), 393–403.
Abstract: This study investigated the ability of chimpanzees, gorillas, orangutans, and bonobos to make inferences by exclusion using the procedure pioneered by Premack and Premack (Cognition 50:347-362, 1994) with chimpanzees. Thirty apes were presented with two different food items (banana vs. grape) on a platform and covered with identical containers. One of the items was removed from the container and placed between the two containers so that subjects could see it. After discarding this item, subjects could select between the two containers. In Experiment 1, apes preferentially selected the container that held the item that the experimenter had not discarded, especially if subjects saw the experimenter remove the item from the container (but without seeing the container empty). Experiment 3 in which the food was removed from one of the containers behind a barrier confirmed these results. In contrast, subjects performed at chance levels when a stimulus (colored plastic chip: Exp. 1; food item: Exp. 2 and Exp. 3) designated the item that had been removed. These results indicated that apes made inferences, not just learned to use a discriminative cue to avoid the empty container. Apes perceived and treated the item discarded by the experimenter as if it were the very one that had been hidden under the container. Results suggested a positive relationship between age and inferential ability independent of memory ability but no species differences.
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Sturz, B. R., Bodily, K. D., & Katz, J. S. (2006). Evidence against integration of spatial maps in humans. Anim. Cogn., 9(3), 207–217.
Abstract: A dynamic 3-D virtual environment was constructed for humans as an open-field analogue of Blaisdell and Cook's (2005) pigeon foraging task to determine if humans, like pigeons, were capable of integrating separate spatial maps. Participants used keyboard keys and a mouse to search for a hidden goal in a 4x4 grid of raised cups. During Phase 1 training, a goal was consistently located between two landmarks (Map 1: blue T and red L). During Phase 2 training, a goal was consistently located down and left of a single landmark (Map 2: blue T). Transfer trials were then conducted in which participants were required to make choices in the presence of the red L alone. Cup choices during transfer assessed participants' strategies: association (from Map 1), generalization (from Map 2), or integration (combining Map 1 and 2). During transfer, cup choices increased to a location which suggested an integration strategy and was consistent with results obtained with pigeons. However, additional analyses of the human data suggested participants initially used a generalization strategy followed by a progressive shift in search behavior away from the red L. This shift in search behavior during transfer was responsible for the changes in cup choices across transfer trials and was confirmed by a control condition. These new analyses offer an alternative explanation to the spatial integration account proposed for pigeons.
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Horowitz, A. C. (2003). Do humans ape? Or do apes human? Imitation and intention in humans (Homo sapiens) and other animals. J Comp Psychol, 117(3), 325–336.
Abstract: A. Whiten, D. M. Custance, J.-C. Gomez, P. Teixidor, and K. A. Bard (1996) tested chimpanzees' (Pan troglodytes) and human children's (Homo sapiens) skills at imitation with a 2-action test on an “artificial fruit.” Chimpanzees imitated to a restricted degree; children were more thoroughly imitative. Such results prompted some to assert that the difference in imitation indicates a difference in the subjects' understanding of the intentions of the demonstrator (M. Tomasello, 1996). In this experiment, 37 adult human subjects were tested with the artificial fruit. Far from being perfect imitators, the adults were less imitative than the children. These results cast doubt on the inference from imitative performance to an ability to understand others' intentions. The results also demonstrate how any test of imitation requires a control group and attention to the level of behavioral analysis.
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Menzel, E. W. J. (1971). Communication about the environment in a group of young chimpanzees. Folia Primatol (Basel), 15(3), 220–232.
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