Abstract: Animals with eyes placed laterally on their head would respond differently to stimuli detected on their different sides. Visual cues from the left eye are processed in the right hemisphere which controls the intensive emotion expression and fast response to the stimuli, while the left hemisphere receiving the information from the contralateral eye is responsible for the routine behaviour and concentration. Different use of left/right eye for exploring environment and evaluation of different stimuli was recently described in domestic horses. They use left eye predominantly for watching novel object or frightening stimulus which indicates specialization of right hemisphere (RH) for appraisal of these types of stimuli. We presumed such lateralisation also in foals during suckling when only monocular vision can be employed for observing surroundings (foals suck mostly in antiparallel body position). Two mutually exclusive hypotheses about the origin of probable foal’s preference for particular suckling side were postulated: 1) visual lateralization, then the foals should suck more often from the mother’s right side (‘from right’), so as potential danger would be detected by the better adapted right hemisphere (i.e. left eye); 2) motor lateralization (the analogous concept as human “handness”), then a foal should suck predominantly from one side, either left or right, more often. Within two seasons, suckling behaviour of 59 Kladruby mares giving birth to 79 foals was observed from deliveries to abrupt weaning (4-7 months of age). From 10 607 recorded suckling solicitations, 50.2% were performed from right, thus there was no preference of the suckling side on a population level. However, we found large variability in the probability of suckling from right among individual foals (p<0.0001); the probability ranged from 0.22-0.98. One third of the foals (35.4%) showed strong, either right (N=13) or left (N=15) side preference which further strengthened with age (interaction suckling side preference*foal’s age: p<0.0001). Other tested variables, i.e. sex of the foal, age of the mother and identity of the herd were not significant. The probability that the mother rejected foal’s suckling solicitation (N=108) did not differ according to the suckling side (right/left) or suckling side preference (right/left/no preference). Suckling bout duration was not significantly influenced neither by the suckling side nor suckling side preference regardless the mother or the foal terminated the suckling bout. In conclusion, only 16 % of the foals revealed significant right side preference for suckling while 19 % left side and 65 % no preference. Thus, we can reject the visual hypothesis because a general trait to suck with left eye open for better danger detection and recognition is unlikely to occur, at least in up to 7 months old foals. Such a young foal is probably fully focused on suckling and relies on mother’s vigilance. Observed individual side preferences indicated more likely a kind of motor lateralization in part of the foals. Further research is needed to clear up the effects of age and individual experience of the foal. Supported by AWIN, EU FP7 project No. 266213.

Abstract: The conflicting results regarding the study of motor laterality in horses may indicate that there does not exist a proper method to assess the degree and the direction of motor bias in these animals. Unfortunately, even less is known about the development of laterality in horses, and to what extent early manipulations can still exert their effects in adulthood. We propose a new method that can be easily applied at a very early age thus avoiding testing adult horses eventually biased by human handling and/or training. Forty-six horses (29 nine-month-old foals and 17 two-year old horses) were handled since birth bilaterally and housed in groups in wide areas. At the time of the analysis, in order to minimize environmental and sensorial disturbances, each horse was tested in a round pen individually or as dyad mother-foal. The ability/inability to properly execute a circle at trot was then recorded, assuming the direction of derailment, i.e. the cutting of the circle, as an indicator of motor bias. From the results of the study it is arguable that motor laterality in horses is acquired over time: in fact foals tested while their mothers were being subjected to longeing showed a higher percentage of ambidextrous animals, while two-year-old horses appeared biased toward the right (p<0.05). Results are discussed in the light of the scientific knowledge about equine biomechanics, taking into account horses' locomotion that leads to the advancement of the body mass through the activation of a kinetic chain that originates from the hindquarters.

Abstract: The authors tested the hypothesis that activity inhibition (AI), a measure of the frequency of the word “not” in written material, marks a propensity to engage functions of the right hemisphere (RH) and disengage functions of the left hemisphere (LH), particularly during stress. Study 1 and Study 2 showed that high AI predicts faster detection of stimuli presented to the RH, relative to the LH. Study 2 provided evidence that the AI-laterality effect is specific to perceptual, but not motor, laterality and that it is particularly strong in individuals with low mood, but absent in individuals in a positive mood state. Study 3 showed that negative affective stimuli prime the AI-laterality effect more strongly than positive affective stimuli. Findings from Study 4 suggest that situationally induced frustration (losing a contest), in conjunction with high AI, leads to increased attentional laterality. The present findings substantially bolster the construct validity of AI and contribute to a better understanding of earlier findings linking AI to physiological stress responses, immune system functioning, alcohol abuse, and nonverbal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)

Abstract: Horses are one-sided, not only on a motor level, but they also prefer to use one eye, ear or nostril over the other under particular circumstances. Horses usually prefer using the left eye to observe novel objects and humans. This preference is more marked in emotional situations and when confronted with unknown persons. Thus the horse’s visual laterality provides a good option for assessing its mental state during training or in human-horse interactions. A strong preference for the left eye may signal that a horse cannot deal with certain training situations or is emotionally affected by a particular person.
Pferde benutzen für die Begutachtung von Objekten und Menschen bevorzugt eine bestimmte Nüster, ein Ohr oder ein Auge. So betrachten die meisten Pferde Objekte und Menschen mit dem linken Auge. Die Lateralitätsforschung erklärt diese sensorische Lateralität mit der Verarbeitung von Informationen unterschiedlicher Qualität in verschiedenen Gehirnhälften und zeigt auf, dass positive und negative emotionale Informationen sowie soziale Sachverhalte mit dem linken Auge aufgenommen und vorwiegend an die rechte Gehirnhälfte weitergegeben werden. In diesem Zusammenhang ermöglicht die visuelle Lateralität, den Gemütszustand des Pferdes im Training und im therapeutischen Fördereinsatz zu erkennen und zu berücksichtigen.

Abstract: Over the past 2 decades, numerous studies have been undertaken to assess motor laterality in the domestic dog. In anticipation of growth in this area of enquiry, we decided to review the literature on canine motor biases to identify any shortcomings, reflect on the lessons to be learned from and offer ways forward for future research into canine laterality. The aim of this review is to (i) summarize motor laterality findings in the dog, (ii) highlight areas lacking in standardization, and (iii) propose necessary criteria for future tests and global reporting protocols. Our review of the literature highlighted the lack of standardization between studies in task selection, sample size, number of behavior scores recorded, and the methods by which motor laterality were classified and reported. This review illustrates the benefits of standardizing methods of motor laterality assessment so that comparisons can be made between the populations sampled. By adopting such an approach, researchers should mutually benefit as motor laterality data could then be compared and subjected to meta-analysis.