Abstract: ABSTRACT: BACKGROUND: It has been suggested that the functional similarities in the socio-cognitive behaviour of dogs and humans emerged as a consequence of comparable environmental selection pressures. Here we use a novel approach to account for the facilitating effect of domestication in dogs and reveal that selection for two factors under genetic influence (visual cooperation and focused attention) may have led independently to increased comprehension of human communicational cues. METHOD: In Study 1, we observed the performance of three groups of dogs in utilizing the human pointing gesture in a two-way object choice test. We compared breeds selected to work while visually separated from human partners (N = 30, 21 breeds, clustered as independent worker group), with those selected to work in close cooperation and continuous visual contact with human partners (N = 30, 22 breeds, clustered as cooperative worker group), and with a group of mongrels (N = 30).Secondly, it has been reported that, in dogs, selective breeding to produce an abnormal shortening of the skull is associated with a more pronounced area centralis (location of greatest visual acuity). In Study 2, breeds with high cephalic index and more frontally placed eyes (brachycephalic breeds, N = 25, 14 breeds) were compared with breeds with low cephalic index and laterally placed eyes (dolichocephalic breeds, N = 25, 14 breeds). RESULTS: In Study 1, cooperative workers were significantly more successful in utilizing the human pointing gesture than both the independent workers and the mongrels.In study 2, we found that brachycephalic dogs performed significantly better than dolichocephalic breeds. DISCUSSION: After controlling for environmental factors, we have provided evidence that at least two independent phenotypic traits with certain genetic variability affect the ability of dogs to rely on human visual cues. This finding should caution researchers against making simple generalizations about the effects of domestication and on dog-wolf differences in the utilization of human visual signals.

Abstract: Two previous studies, Martin et al. (J. Exp. Psychol. Anim. Behav. Process. 23 (1997) 183) and Dudchenko et al. (J. Exp. Psychol. Anim. Behav. Process. 23 (1997) 194), report that, compared to non-disoriented controls, rats disoriented before testing were disrupted in their ability to learn the location of a goal on a dry radial-arm maze task, but that both groups learned at the same rate in the Morris water maze. However, the radial-arm maze task was much more difficult than the water maze. In the current set of experiments, we examined the performance of control and disoriented rats on more comparable dry land and water maze tasks. Compared to non-disoriented rats, rats that were disoriented before testing were significantly impaired in locating a goal in a circular dry arena, but not a water tank. The results constrain theoretical explanations for the differential effects of disorientation on different spatial tasks.

Abstract: Associative learning theories presume the existence of a general purpose learning process, the structure of which does not mirror the demands of any particular learning problem. In contrast, learning scientists working within an Evolutionary Biology tradition believe that learning processes have been shaped by ecological demands. One potential means of exploring how ecology may have modified properties of acquisition is to use associative learning theory as a framework within which to analyse a particular learning phenomenon. Recent work has used this approach to examine whether socially transmitted predator avoidance can be conceptualised as a classical conditioning process in which a novel predator stimulus acts as a conditioned stimulus (CS) and acquires control over an avoidance response after it has become associated with alarm signals of social companions, the unconditioned stimulus (US). I review here a series of studies examining the effect of CS/US presentation timing on the likelihood of acquisition. Results suggest that socially acquired predator avoidance may be less sensitive to forward relationships than traditional classical conditioning paradigms. I make the case that socially acquired predator avoidance is an exciting novel one-trial learning paradigm that could be studied along side fear conditioning. Comparisons between social and non-social learning of danger at both the behavioural and neural level may yield a better understanding of how ecology might shape properties and mechanisms of learning.

Abstract: When asked to hold a young infant in their arms, most adults hold on the left side (Harris, 1997). In a prior study, we found the same bias when we asked adults merely to imagine holding an infant in their arms (Harris, Almerigi, & Kirsch, 1999). It has been hypothesized that the left-side bias is the product of right-hemisphere arousal accompanying certain aspects of the act, causing attention to be driven to the contralateral, or left, side of personal space. Left-side holding, whether actual or imagined, thus would be consistent with the direction to which the holder's attention has been endogenously directed. We tested this hypothesis by giving 250 college students the “imagine-holding” task and then, as an independent measure of lateralized hemispheric arousal, a 34-item Chimeric Faces Test (CFT). On the “imagine” test, a significant majority reported a left-side hold, and, on the CFT, left-side holders had a significantly stronger left-hemispace bias than right-side holders, although both left- and right- side holders had left-hemispace CFT biases. The results thus support the attentional-arousal hypothesis but indicate that other factors are contributing as well.

Abstract: The species assemblages of cichlids in the three largest African Great Lakes are among the richest concentrations of vertebrate species on earth. The faunas are broadly similar in terms of trophic diversity, species richness, rates of endemism, and taxonomic composition, yet they are historically independent of each other. Hence, they offer a true and unique evolutionary experiment to test hypotheses concerning the mutual dependencies of ecology and brain morphology. We examined the brains of 189 species of cichlids from the three large lakes: Victoria, Tanganyika, and Malawi. A first paper demonstrated that patterns of evolutionary change in cichlid brain morphology are similar across taxonomic boundaries as well as across the three lakes [van Staaden et al., 1995 ZACS 98: 165–178]. Here we report a close relationship between the relative sizes of various brain structures and variables related to the utilization of habitat and prey. Causality is difficult to assign in this context, nonetheless, prey size and agility, turbidity levels, depth, and substrate complexity are all highly predictive of variation in brain structure. Areas associated with primary sensory functions such as vision and taste relate significantly to differences in feeding habits. Turbidity and depth are closely associated with differences in eye size, and large eyes are associated with species that pick plankton from the water column. Piscivorous taxa and others that utilize motile prey are characterized by a well developed optic tectum and a large cerebellum compared to species that prey on molluscs or plants. Structures relating to taste are well developed in species feeding on benthos over muddy or sandy substrates. The data militated against the existence of compensatory changes in brain structure. Thus enhanced development of a particular function is generally not accompanied by a parallel reduction of structures related to other modalities. Although genetic and environmental influences during ontogeny of the brain cannot be isolated, this study provides a rich source of hypotheses concerning the way the nervous system functions under various environmental conditions and how it has responded to natural selection.