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Farmer, K., Krueger, K., & Byrne, R. (2010). Visual laterality in the domestic horse (Equus caballus) interacting with humans. Anim. Cogn., 13, 229–238.
Abstract: Most horses have a side on which they are easier to handle and a direction they favour when working on a circle, and recent studies have suggested a correlation between emotion and visual laterality when horses observe inanimate objects. As such lateralisation could provide important clues regarding the horse’s cognitive processes, we investigated whether horses also show laterality in association with people. We gave horses the choice of entering a chute to left or right, with and without the passive, non-interactive presence of a person unknown to them. The left eye was preferred for scanning under both conditions, but significantly more so when a person was present. Traditionally, riders handle horses only from the left, so we repeated the experiment with horses specifically trained on both sides. Again, there was a consistent preference for left eye scanning in the presence of a person, whether known to the horses or not. We also examined horses interacting with a person, using both traditionally and bilaterally trained horses. Both groups showed left eye preference for viewing the person, regardless of training and test procedure. For those horses tested under both passive and interactive conditions, the left eye was preferred significantly more during interaction. We suggest that most horses prefer to use their left eye for assessment and evaluation, and that there is an emotional aspect to the choice which may be positive or negative, depending on the circumstances. We believe these results have important practical implications and that emotional laterality should be taken into account in training methods.
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Ruiz, A., Gómez, J., Roeder, J., & Byrne, R. (2009). Gaze following and gaze priming in lemurs. Anim. Cogn., 12(3), 427–434.
Abstract: Abstract  Although primates have often been found to co-orient visually with other individuals, members of these same species have usually failed to use co-orientation to find hidden food in object-choice experiments. This presents an evolutionary puzzle: what is the function of co-orientation if it is not used for a function as basic as locating resources? Co-orientation responses have not been systematically investigated in object-choice experiments, and requiring co-orientation with humans (as is typical in object-choice tasks) may underestimate other species’ abilities. Using an object-choice task with conspecific models depicted in photographs, we provide experimental evidence that two lemur species (Eulemur fulvus, n = 4, and Eulemur macaco, n = 2) co-orient with conspecifics. Secondly, by analysing together two measures that have traditionally been examined separately, we show that lemurs’ gaze following behaviour and ultimate choice are closely linked. Individuals were more likely to choose correctly after having looked in the same direction as the model, and thus chose objects correctly more often than chance. We propose a candidate system for the evolutionary origins of more complex gaze following: ‘gaze priming.’
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Byrne, R. W. (2009). Animal imitation. Current Biology, 19(3), R111–R114.
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Byrne, R. W., & Bates, L. A. (2006). Why are animals cognitive? Curr Biol, 16(12), R445–8.
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Bates, L. A., Sayialel, K. N., Njiraini, N. W., Poole, J. H., Moss, C. J., & Byrne, R. W. (2008). African elephants have expectations about the locations of out-of-sight family members. Biol Lett, 4(1), 34–36.
Abstract: Monitoring the location of conspecifics may be important to social mammals. Here, we use an expectancy-violation paradigm to test the ability of African elephants (Loxodonta africana) to keep track of their social companions from olfactory cues. We presented elephants with samples of earth mixed with urine from female conspecifics that were either kin or unrelated to them, and either unexpected or highly predictable at that location. From behavioural measurements of the elephants' reactions, we show that African elephants can recognize up to 17 females and possibly up to 30 family members from cues present in the urine-earth mix, and that they keep track of the location of these individuals in relation to themselves.
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Janson, C., & Byrne, R. (2007). What wild primates know about resources: opening up the black box. Anim. Cogn., 10(3), 357–367.
Abstract: Abstract We present the theoretical and practical difficulties of inferring the cognitive processes involved in spatial movement decisions of primates and other animals based on studies of their foraging behavior in the wild. Because the possible cognitive processes involved in foraging are not known a priori for a given species, some observed spatial movements could be consistent with a large number of processes ranging from simple undirected search processes to strategic goal-oriented travel. Two basic approaches can help to reveal the cognitive processes: (1) experiments designed to test specific mechanisms; (2) comparison of observed movements with predicted ones based on models of hypothesized foraging modes (ideally, quantitative ones). We describe how these two approaches have been applied to evidence for spatial knowledge of resources in primates, and for various hypothesized goals of spatial decisions in primates, reviewing what is now established. We conclude with a synthesis emphasizing what kinds of spatial movement data on unmanipulated primate populations in the wild are most useful in deciphering goal-oriented processes from random processes. Basic to all of these is an estimate of the animals ability to detect resources during search. Given knowledge of the animals detection ability, there are several observable patterns of resource use incompatible with a pure search process. These patterns include increasing movement speed when approaching versus leaving a resource, increasingly directed movement toward more valuable resources, and directed travel to distant resources from many starting locations. Thus, it should be possible to assess and compare spatial cognition across a variety of primate species and thus trace its ecological and evolutionary correlates.
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Byrne, R. W. (2007). Culture in great apes: using intricate complexity in feeding skills to trace the evolutionary origin of human technical prowess. Phil. Trans. Biol. Sci., 362(1480), 577–585.
Abstract: Geographical cataloguing of traits, as used in human ethnography, has led to the description of “culture” in some non-human great apes. Culture, in these terms, is detected as a pattern of local ignorance resulting from environmental constraints on knowledge transmission. However, in many cases, the geographical variations may alternatively be explained by ecology. Social transmission of information can reliably be identified in many other animal species, by experiment or distinctive patterns in distribution; but the excitement of detecting culture in great apes derives from the possibility of understanding the evolution of cumulative technological culture in humans. Given this interest, I argue that great ape research should concentrate on technically complex behaviour patterns that are ubiquitous within a local population; in these cases, a wholly non-social ontogeny is highly unlikely. From this perspective, cultural transmission has an important role in the elaborate feeding skills of all species of great ape, in conveying the “gist” or organization of skills. In contrast, social learning is unlikely to be responsible for local stylistic differences, which are apt to reflect sensitive adaptations to ecology.
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Held, S., Mendl, M., Devereux, C., & Byrne, R. W. (2001). Studies in Social Cognition: From Primates to Pigs. Animal Welfare, 10, 209–217.
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Valero, A., & Byrne, R. (2007). Spider monkey ranging patterns in Mexican subtropical forest: do travel routes reflect planning? Anim. Cogn., 10(3), 305–315.
Abstract: Although it is well known that frugivorous spider monkeys (Ateles geoffroyi yucatanensis) occupy large home ranges, travelling long distances to reach highly productive resources, little is known of how they move between feeding sites. A 11 month study of spider monkey ranging patterns was carried out at the Otochma’ax Yetel Kooh reserve, Yucatán, Mexico. We followed single individuals for as long as possible each day and recorded the routes travelled with the help of a GPS (Global Positioning System) device; the 11 independently moving individuals of a group were targeted as focal subjects. Travel paths were composed of highly linear segments, each typically ending at a place where some resource was exploited. Linearity of segments did not differ between individuals, and most of the highly linear paths that led to food resources were much longer than the estimate visibility in the woodland canopy. Monkeys do not generally continue in the same ranging direction after exploiting a resource: travel paths are likely to deviate at the site of resource exploitation rather than between such sites. However, during the harshest months of the year consecutive route segments were more likely to retain the same direction of overall movement. Together, these findings suggest that while moving between feeding sites, spider monkeys use spatial memory to guide travel, and even plan more than one resource site in advance.
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Byrne, R. W., Corp, N., & Byrne, J. M. (2001). Manual dexterity in the gorilla: bimanual and digit role differentiation in a natural task. Anim. Cogn., 4(3), 347–361.
Abstract: The manipulative actions of mountain gorillas Gorilla g. beringei were examined in the context of foraging on hard-to-process plant foods in the field, in particular those used in tackling thistle Carduus nyassanus. A repertoire of 72 functionally distinct manipulative actions was recorded. Many of these actions were used in several variants of grip, finger(s) and movement path, both by different individuals and by the same individual at different times. The repertoire appears somewhat greater than that observed in comparable studies of monkeys, but a far more striking difference is found in the use of differentiated actions in concert. Mountain gorillas routinely and frequently deal with problems that involve: (1) bimanual role differentiation, with the two hands taking different roles but synchronized in time and space, and (2) digit role differentiation, with independent control of parts of the same hand used for separate purposes at the same time. The independent control that allows these abilities, so crucial to human manual constructional ability, is apparently general in African great apes. Role differentiation, between and within the hand, is evidently a primitive characteristic in the human arsenal of skills.
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