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Humans are distinguished from the other living apes in having larger brains and an unusual life history that combines high reproductive output with slow childhood growth and exceptional longevity (1). [...]

Preference for tools with either rigid or flexible properties was explored in orangutans (Pongo spp.) through an extension of D. J. Povinelli, J. E. Reaux, and L. A. Theall's (2000) flimsy-tool problem. Three captive orangutans were presented with three unfamiliar pairs of tools to solve a novel problem. Although each orangutan has spontaneously used tools in the past, the tools presented in this study were novel to the apes. Each pair of tools contained one tool with rigid properties (functional) and one tool with flimsy properties (nonfunctional). Solving the problem required selection of a rigid tool to retrieve a food reward. The functional tool was selected in nearly all trials. Moreover, two of the orangutans demonstrated this within the first test trials with each of the three tool types. Although further research is required to test this statistically, it suggests either a preexisting preference for rigid tools of comprehension of the relevant features required in a tool to solve the task. The results of this study demonstrate that orangutans can recognize, or learn to recognize, relevant tool properties and can choose an appropriate tool to solve a problem. Keywords: tool use, tool properties, orangutan, ape, cognition DOI: 10.1037/a0019566

The ability to share attention with another is the foundation on which other theory of mind skills are formed. The quality of care received during infancy has been correlated with increased joint attention in humans. The purpose of this study was to assess the effects of care style (responsive or basic) and caregiver type (ape or human) during the first 6 months on joint attention in 4 great ape species (Pan troglodytes, Gorilla gorilla, Pongo spp., and Pan pansicus). Great apes engaged in joint attention with conspecifics and humans regardless of the style of early care they experienced from either a great ape mother or human caregiver. This finding suggests that joint attention is a robust ability in great apes that is resilient against at least some differences in early care. Future studies using additional measures of early care quality are recommended. Keywords: joint attention, gaze following, theory of mind, attachment theory, great apes

Rhesus monkeys (Macaca mulatta) develop strategies to acquire and execute serial lists (K. B. Swartz & S. A. Himmanen, 2001). Serial probe recognition studies of list memory have demonstrated similarities across monkeys and humans (S. F. Sands & A. A. Wright, 1980). The present study extended the investigation of list learning and memory to determine whether orangutans (Pongo pygmaeus x P. abelii) would show evidence of subjective organization of photographic lists in a manner similar to that shown by humans learning a list of unrelated words (E. Tulving, 1962). No evidence for the effective use of a subjective organization strategy was found, but the orangutans developed a right-to-left spatial response strategy, which emerged during the acquisition of 5-item lists. This strategy was an effective way to reduce the load on working memory when presented with a complex array of items. Keywords: list memory, strategy, ape, orangutan, Pongo

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2004.04.022 Byline: Daniel J. Shillito, Robert W. Shumaker, Gordon G. Gallup, Benjamin B. Beck Abstract: An adult female orang-utan used an untutored series of physical manipulations to guide humans to food placed beyond her reach. Through a series of experiments that involved different visual occlusions, this orang-utan appeared to take into account humans' visual states when using them to retrieve inaccessible goals. These data suggest that she was able to use her experience with visual barriers to model the visual perspective of visually impaired humans in a manner similar to that of 2- to 3-year-old human children. Author Affiliation: (*) Animal Forest, South Carolina State Park Service and Masters of Environmental Science Department, University of Charleston, U.S.A. (a ) Iowa Primate Learning Sanctuary, Des Moines, IA, U.S.A. (a ) Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA, U.S.A. (As.) Department of Psychology, University at Albany, State University of New York, U.S.A. Article History: Received 2 October 2003; Revised 12 November 2003; Accepted 24 April 2004 Article Note: (miscellaneous) MS. number: A9726

The ability to discriminate quantity is descriptive of general cognitive ability. In this study, the authors presented 2 orangutans (Pongo pygmaeus) with a quantity judgment task. Each trial consisted of 2 choices, ranging from 1 to 6 food items in each. The orangutan chose 1 of the quantities, which was removed, and the remaining array was given as a reward. In contrast to chimpanzees previously tested on the same task (S. T. Boysen & G. G. Berntson, 1995; S. T. Boysen, G. G. Berntson, M. B. Hannah, & J. T. Cacioppo, 1996; S. T. Boysen, K. L. Mukobi, & G. G. Berntson, 1999), the orangutans optimized their performance. Orangutans, therefore, attend to differences in magnitude and can spontaneously use ordinality. Results also suggest a cognitive difference between chimpanzees and orangutans.

Humans crave categorical distinctions. One of the most common is separating ourselves from the 'animals.' This dichotomy is not surprising given the historical view that placed us in the unique [...]