Brannon, E. M., & Terrace, H. S. (1998). Ordering of the numerosities 1 to 9 by monkeys. Science, 282(5389), 746–749.
Abstract: A fundamental question in cognitive science is whether animals can represent numerosity (a property of a stimulus that is defined by the number of discriminable elements it contains) and use numerical representations computationally. Here, it was shown that rhesus monkeys represent the numerosity of visual stimuli and detect their ordinal disparity. Two monkeys were first trained to respond to exemplars of the numerosities 1 to 4 in an ascending numerical order (1 --> 2 --> 3 --> 4). As a control for non-numerical cues, exemplars were varied with respect to size, shape, and color. The monkeys were later tested, without reward, on their ability to order stimulus pairs composed of the novel numerosities 5 to 9. Both monkeys responded in an ascending order to the novel numerosities. These results show that rhesus monkeys represent the numerosities 1 to 9 on an ordinal scale.
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Packer, C., & Heinsohn, R. (1996). Response:Lioness leadership. Science, 271(5253), 1215–1216.
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Gary C. Jahn, & Craig Packer, R. H. (1996). Lioness leadership. Science, 271(5253), 1216–1219.
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Thornton, A., & McAuliffe, K. (2006). Teaching in wild meerkats. Science, 313(5784), 227–229.
Abstract: Despite the obvious benefits of directed mechanisms that facilitate the efficient transfer of skills, there is little critical evidence for teaching in nonhuman animals. Using observational and experimental data, we show that wild meerkats (Suricata suricatta) teach pups prey-handling skills by providing them with opportunities to interact with live prey. In response to changing pup begging calls, helpers alter their prey-provisioning methods as pups grow older, thus accelerating learning without the use of complex cognition. The lack of evidence for teaching in species other than humans may reflect problems in producing unequivocal support for the occurrence of teaching, rather than the absence of teaching.
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Singh, M., Singh, M., Sharma, A. K., & Krishna B. A. (2003). Methodological considerations in measurement of dominance in primates. CURRENT SCIENCE, 84(5), 709–713.
Abstract: The strength of dominance hierarchy in a group of
animals needs to be quantitatively measured since it
influences many other aspects of social interactions.
This article discusses three attempts made by previous
researchers to measure the strength of hierarchy. We
propose a method which attempts to rectify the lacunae
in the previous attempts. Data are used from a
group of Japanese macaques housed in a colony. A
method to calculate strength of hierarchy has been
illustrated and a procedure has been suggested to
normalize the dominance scores in order to place the
ranks of individuals on an interval scale.
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Emery, N. J., & Clayton, N. S. (2004). The Mentality of Crows: Convergent Evolution of Intelligence in Corvids and Apes. Science, 306(5703), 1903–1907.
Abstract: Discussions of the evolution of intelligence have focused on monkeys and apes because of their close evolutionary relationship to humans. Other large-brained social animals, such as corvids, also understand their physical and social worlds. Here we review recent studies of tool manufacture, mental time travel, and social cognition in corvids, and suggest that complex cognition depends on a “tool kit” consisting of causal reasoning, flexibility, imagination, and prospection. Because corvids and apes share these cognitive tools, we argue that complex cognitive abilities evolved multiple times in distantly related species with vastly different brain structures in order to solve similar socioecological problems.
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Jolly, A. (1966). Lemur social behavior and primate intelligence. Science, 153(3735), 501–506.
Abstract: Our human intellect has resulted from an enormous leap in capacity above the level of monkeys and apes. Earlier, though, Old and New World monkeys' intelligence outdistanced that of other mammals, including the prosimian primates. This first great advance in intelligence probably was selected through interspecific competition on the large continents. However, even at this early stage, primate social life provided the evolutionary context of primate intelligence.
Two arguments support this conclusion. One is ontogenetic: modern monkeys learn so much of their social behavior, and learn their behavior toward food and toward other species through social example. The second is phylogenetic: some prosimians, the social lemurs, have evolved the usual primate type of society and social learning without the capacity to manipulate objects as monkeys do. It thus seems likely that the rudiments of primate society preceded the growth of primate intelligence, made it possible, and determined its nature.
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Peham, C., Licka, T., Schobesberger, H., & Meschan, E. (2004). Influence of the rider on the variability of the equine gait. European Workshop on Movement Science, 23(5), 663–671.
Abstract: The aim of this study was to show that the motion pattern of a well-ridden horse varies less than the motion pattern of an unridden horse. In order to do so, we recorded the motion of two markers, one attached to the dorsal spinous processus of lumbar vertebra L4, the other to the right fore hoof. In total, we measured 21 horses in trot, ridden and unridden, with a fitting and with a non-fitting saddle. After breaking down the entire time series of the three-dimensional motion of the markers into their respective motion cycles, we computed a measure of motion pattern variability for the motion as well as for the derivatives (velocity and acceleration) along each of the three principal dimensions. Two of six variables (velocity and acceleration in the forward direction) displayed a significant discrimination between the ridden and the unridden case, and demonstrated the beneficial effect of a rider on the horse's motion pattern variability. Saddle fit was shown to have also an influence on motion variability: variability of two variables (velocity and of acceleration in forward direction) was significantly lower with a fitting saddle compared to a non-fitting saddle, a third variable (acceleration in the transversal direction) showed a significant difference also. This new method offers an objective evaluation of saddle fit, and a sensitive assessment of the quality of the rider in the moving horse.
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Silk, J. B. (2007). Social Components of Fitness in Primate Groups. Science, 317(5843), 1347–1351.
Abstract: There is much interest in the evolutionary forces that favored the evolution of large brains in the primate order. The social brain hypothesis posits that selection has favored larger brains and more complex cognitive capacities as a means to cope with the challenges of social life. The hypothesis is supported by evidence that shows that group size is linked to various measures of brain size. But it has not been clear how cognitive complexity confers fitness advantages on individuals. Research in the field and laboratory shows that sophisticated social cognition underlies social behavior in primate groups. Moreover, a growing body of evidence suggests that the quality of social relationships has measurable fitness consequences for individuals.
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Pennisi, E. (2007). PSYCHOLOGY: Nonhuman Primates Demonstrate Humanlike Reasoning. Science, 317(5843), 1308–.
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