Abstract: To determine whether wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) at Mikura Island, Japan, show asymmetry of eye or flipper use during a social behaviour, we investigated the laterality of flipper-to-body (F-B) rubbing, in which one dolphin (“rubber”) rubs the body of another (“rubbee”) with its flipper. We analysed 382 episodes of video-recorded F-B rubbings performed by identified individuals (N = 111 rubbers). F-B rubbing was conducted significantly more frequently with the left flipper than with the right flipper. The duration of F-B rubbings was also significantly longer with the left flipper than with the right flipper. Of 20 dolphins, nine individuals showed significant left-side bias as the rubber in this behaviour, whereas no dolphins showed significant right-side bias. The results indicate a population-level left-side bias of the rubber in F-B rubbing. An analysis of the swimming configurations during this behaviour suggests that the asymmetry in F-B rubbing was caused not only by the laterality of the rubber, but by a preference for use of the left eye in both dolphins during this behaviour. Dolphins used the left eye significantly more frequently than the right eye during the inquisitive behaviour, while they showed no significant bias in flipper use during the object-carrying behaviour. These facts also suggest that the asymmetry of F-B rubbing is caused by the preference for using the left eye. Significant left-side bias was observed only in F-B rubbings initiated by the rubbee, in which the rubbee determined its position during this behaviour. This suggests that this behavioural asymmetry was enhanced by the rubbees choosing the left side of the rubber to ensure better and longer rubs.

Abstract: Lateralization of the brain appeared early in evolution and many of its features appear to have been retained, possibly even in humans. We now have a considerable amount of information on the different forms of lateralization in a number of species, and the commonalities of these are discussed, but there has been relatively little investigation of the advantages of being lateralized. This article reports new findings on the differences between lateralized and nonlateralized chicks. The lateralized chicks were exposed to light for 24 h on day 19 of incubation, a treatment known to lead to lateralization of a number of visually guided responses, and the nonlateralized chicks were incubated in the dark. When they were feeding, the lateralized chicks were found to detect a stimulus resembling a raptor with shorter latency than nonlateralized chicks. This difference was not a nonspecific effect caused by the light-exposed chicks being more distressed by the stimulus. Instead, it appears to be a genuine advantage conferred by having a lateralized brain. It is suggested that having a lateralized brain allows dual attention to the tasks of feeding (right eye and left hemisphere) and vigilance for predators (left eye and right hemisphere). Nonlateralized chicks appear to perform these dual tasks less efficiently than lateralized ones. Reference is made to other species in discussing these results.

Abstract: Two experiments investigated the effects of haptic and visual discrimination on hand preference in 22 brown capuchin monkeys (Cebus apella). The percentage of left-handed subjects in Experiment 1 were 63.6%, 45.5%, and 18.2% for haptic, bipedal, and quadrupedal reaching, respectively. In Experiment 2, the haptic demands of the task were manipulated by using additional food types and another tactile medium. Left-hand preferences were further strengthened when reaching into water compared to pineshavings in Experiment 1. Reaching with no tactile interference resulted in equal numbers of lateralized and nonlateralized subjects. These results show that when reaching demands the use of haptic cues, as opposed to visual ones, monkeys shift towards greater left hand use. This is consistent with what is known about right hemisphere superiority for haptic discrimination in humans.

Abstract: This study examined the relationship between motor laterality in horses bred for different types of work and therefore different temperaments. Foreleg preference during grazing was measured in three populations of domestic horse, Thoroughbreds (TB, bred to race at the gallop), Standardbreds (SB, bred for pacing) and Quarter Horses (QH, in this case bred for so-called “cutting work” which involves manoeuvring individual cattle in and out of herds). With a one-sample t-test, TBs showed strong evidence of a left preference in motor laterality (P = 0.000), as did SBs (P = 0.002) but there was no convincing evidence for laterality in QH (P = 0.117). However, the increasing trend in left preference from QH to SBs then TBs was associated with increasing differences between individual horses within a breed. The overall preference (either left or right) increased with age (P = 0.008) and the rate of increase varied with breeds. The presence of a higher proportion of left-foreleg preferent individuals in TBs and SBs compared with QH may indicate that their training or selection (or both) has an effect on motor bias.

Abstract: A number of nonhuman primate species have demonstrated the ability to use a joystick to control a cursor on a computer screen, yet the acquisition of this skill has not been the focus of systematic inquiry. Here, we examined joystick acquisition in four tufted capuchins under two directional relationships of joystick movement and resultant cursor displacement, isomorphic and inverted. To document the natural history of the acquisition of this skill, we recorded the development of visual tracking of the cursor and body tilting. Rates of acquisition were comparable between the two conditions. After mastering the task in one condition, subjects remastered the task at an accelerated rate in the opposing condition. All subjects significantly increased or maintained high proportions of cursor tracking throughout acquisition. All subjects demonstrated a postural tilt while moving the cursor from the mid-phase of acquisition through task mastery. In the isomorphic condition, all subjects tilted significantly more often in the direction of goal location than in the opposite direction. In three of the four series of tilting that were scored for subjects in the inverted condition, tilting occurred significantly more often toward the direction of goal location than the direction of required hand movement. Together these findings suggest that body tilting participates in the organization of directional movement of the cursor rather than reflecting merely the motoric requirements of the task (to manipulate a joystick).