Manual lateralization in macaques: handedness, target laterality and task complexity

Methodological comparison of cancellation versus two-way choice spatial attention tests in humans and dogs

Introduction

Behavioural problems in family dogs are amongst the leading reasons for relinquishment to shelters which adversely affects animal welfare. Recent research suggests that certain problematic behavioural patterns might be analogous to human psychiatric disorders. Veterinary diagnosis of such conditions, however, is scarce, probably due to the lack of appropriate measurement tools. The current study focuses on dog behaviour resembling the human hemispatial neglect condition, which manifests itself as a deficit in attention to and awareness of one side of the space.

Methods

Healthy human subjects (N = 21) and adult family dogs (N = 23) were tested with tools aimed to measure spatial attention. Tests administered to humans included validated paper and pencil neuropsychological tools to assess hemispatial neglect (cancellation tasks), as well as the canine version of that task (visuo-spatial search task). Dogs were tested with the same visuo-spatial search task as well as a two-way choice task.

Results

Results show that both in case of dogs and humans the visuo-spatial search task detects individual variation in subjects' side preferences. However, subjects' performance in the different tasks were not related.

Hand preferences in coordinated bimanual tasks in non-human primates: A systematic review and meta-analysis

The evolutionary significance of hand preferences among non-human primates and humans has been studied for decades with the aim of determining the origins of the population-level tendency. In this study, a meta-analysis was conducted to statistically integrate data on hand preferences in non-human primates performing the tube task and other bimanual tasks to determine the presence and direction of manual laterality. Significant individual-level lateralization was obtained for these bimanual tasks. In nonhuman primates, 82% of the animals analysed showed right or left-hand preference performing the tube task, this figure being 90% for other bimanual tasks. In contrast with humans, no asymmetry was found at the population level. Additionally, population-level preferences were not found in either of the tasks, although a strong manual preference was found when performing the tube task and other bimanual tasks. Species was studied as a variable moderator throughout the meta-analysis. These results highlight the importance of standardized testing methodologies across species and institutions to obtain comparable data and fill the gaps in the taxonomy.

Analogous laterality in trunk movements in captive African elephants: A pilot study

Lateralization of hand use in primates has been extensively studied in a variety of contexts, and starts to be investigated in other species and organs in order to understand the evolution of the laterality according to different tasks. In elephants, the orientation of the movements of the trunk has been observed mainly in feeding and social contexts, in free conditions. However, little is known about the influence of task complexity on trunk laterality. In this study, we compared the lateralization of the trunk in two conditions: standardized and free. We offered granules to six African elephants on each side of an opened trapdoor to create a constraining environment and reported the different behaviours employed and their orientation. In addition, we observed the same individuals in free conditions and noted the lateralization of the use of their trunk. We revealed a common right side preference in all our elephants, both in standardized and free conditions. This side bias was stronger in our constraining task, adding evidence for the task complexity theory. We finally described laterality in new behaviours in the literature on elephants, such as pinching, gathering or exploration with the trunk.

Four meta-analyses across 164 studies on atypical footedness prevalence and its relation to handedness

Human lateral preferences, such as handedness and footedness, have interested researchers for decades due to their pronounced asymmetries at the population level. While there are good estimates on the prevalence of handedness in the population, there is no large-scale estimation on the prevalence of footedness. Furthermore, the relationship between footedness and handedness still remains elusive. Here, we conducted meta-analyses with four different classification systems for footedness on 145,135 individuals across 164 studies including new data from the ALSPAC cohort. The study aimed to determine a reliable point estimate of footedness, to study the association between footedness and handedness, and to investigate moderating factors influencing footedness. We showed that the prevalence of atypical footedness ranges between 12.10% using the most conservative criterion of left-footedness to 23.7% including all left- and mixed-footers as a single non-right category. As many as 60.1% of left-handers were left-footed whereas only 3.2% of right-handers were left-footed. Males were 4.1% more often non-right-footed compared to females. Individuals with psychiatric and neurodevelopmental disorders exhibited a higher prevalence of non-right-footedness. Furthermore, the presence of mixed-footedness was higher in children compared to adults and left-footedness was increased in athletes compared to the general population. Finally, we showed that footedness is only marginally influenced by cultural and social factors, which play a crucial role in the determination of handedness. Overall, this study provides new and useful reference data for laterality research. Furthermore, the data suggest that footedness is a valuable phenotype for the study of lateral motor biases, its underlying genetics and neurodevelopment.

The relationship between problem-solving ability and laterality in cats

The association between hemispheric asymmetries and cognitive ability is one of the key areas of comparative laterality research. In several animal species, individual limb preferences correlate with perceptual, cognitive, or motor abilities, possibly by increasing dexterity of one limb and minimizing response conflicts between hemispheres. Despite this wealth of research, the association between laterality and cognitive abilities in the cat (Felis catus) is not well understood. Therefore, it was the aim of the present study to investigate the relationship between laterality and problem-solving ability in cats. To this end, strength and direction of paw preferences in 41 cats were measured using two novel food reaching tasks in which the animals needed to open a lid in order to reach the food reward. We found that cats that showed a clear preference for one paw were able to open more lids succesfully than ambilateral animals. Moreover, cats that preferred to interact with the test apparatus with their paw from the beginning, opened more lids than cats the first tried to interact with the test apparatus using their heads. Results also suggested a predictive validity of the first paw usage for general paw usage. It was also shown that the cats' individual paw preferences were stable and task-independent. These results yield further support to the idea that lateralization may enhance cognitive abilities.

Low survival of strongly footed pheasants may explain constraints on lateralization

Brain lateralization is considered adaptive because it leads to behavioral biases and specializations that bring fitness benefits. Across species, strongly lateralized individuals perform better in specific behaviors likely to improve survival. What constrains continued exaggerated lateralization? We measured survival of pheasants, finding that individuals with stronger bias in their footedness had shorter life expectancies compared to individuals with weak biases. Consequently, weak, or no footedness provided the highest fitness benefits. If, as suggested, footedness is indicative of more general brain lateralization, this could explain why continued brain lateralization is constrained even though it may improve performance in specific behaviors.

Slow lorises (Nycticebus spp.) display evidence of handedness in the wild and in captivity

It has been suggested that strepsirrhines (lemurs, lorises, and galagos) retain the more primitive left-hand preference, whilst monkeys and apes more regularly display a right-hand preference at the individual-level. We looked to address questions of laterality in the slow loris (Nycticebus spp.) using spontaneous observations of 7 wild individuals, unimanual tests in 6 captive individuals, and photos of 42 individuals in a bilateral posture assessing handedness at the individual- and group-level. During the unimanual reach task, we found at the individual-level, only 4 slow lorises showed a hand use bias (R: 3, L: 1), Handedness index (HI) ranged from -0.57 to 1.00. In the wild unimanual grasp task, we found at the individual-level two individual showed a right-hand bias, the HI ranged from -0.19 to 0.70. The bilateral venom pose showed a trend toward a right-hand dominant grip in those photographed in captivity, but an ambiguous difference in wild individuals. There are many environmental constraints in captivity that wild animals do not face, thus data collected in wild settings are more representative of their natural state. The presence of right-handedness in these species suggests that there is a need to re-evaluate the evolution of handedness in primates.

Paw preferences in the Asian small-clawed otter - using an inexpensive, video-based protocol to study laterality of rare species in the zoo

It is still debated whether limb-use preferences represent a common trait in vertebrates, which is based on a shared phylogenetic history. Unravelling the evolutionary origin and pattern of paw preferences in vertebrates requires the analysis of a larger number of species within an ecologically relevant setting. We therefore investigated whether observations in a zoo enable the collection of reliable data sets by quantifying paw use in two independent groups of Asian small-clawed otters (Amblonyx cinerea). Employing a continuous focal animal sampling method, each day one of the ten individuals was video recorded from outside of the enclosure during usual activity. We selected four types of unimanual behaviour (reaching for food, reaching for non-food, reaching into a hole, carrying an object) and quantified paw use for each animal. Our study provides first evidences for individual paw preferences in otters, which were in line with previously reported forelimb use pattern in carnivoran species. Preferences differed between motor acts but for "reaching into a hole" a population-level right paw bias was detected. These data support that observations in a zoological setting are useful to explore task-dependent paw preferences and may facilitate future studies investigating paw preferences under experimentally controlled conditions.