Abstract
ABSTRACTMotor lateralization is hypothesized to depend on the complexity of the motor function, but it might at the same time reflect hemispheric dominance within an individual across motor functions. We investigated possible motor lateralization patterns in four motor functions of different complexity (snout use in a manipulative task, foot use in two-stepping tasks and tail curling) in the domestic pig, a tetrapod species relevant as farm animal but also as a model in human neuroscience. A significant majority of our sample showed individual biases for manipulation with their snout and for curling their tail. Interestingly, the tail curling was lateralized towards the right at the population level and showed stronger lateralization patterns than the snout. Using a cluster analysis with combined tail and snout laterality, we identified groups of individuals with different lateralization patterns across motor functions that potentially reflect the individuals’ hemispheric dominance. To conclude, our results suggest that pigs show lateralization patterns that depend on the motor function and on the individual. Such individual lateralization patterns might have broader implications for animal personality and welfare. Our study lays the methodological groundwork for future research on laterality in pigs.
Highlights
Cerebral asymmetries are widespread in animals and are supposed to have an evolutionary advantage to improve brain efficiency by enabling the brain to LATERALITY: ASYMMETRIES OF BODY, BRAIN AND COGNITION perform more than one task simultaneously (Rogers, Zucca, & Vallortigara, 2004)
Two other subjects were excluded from the tail analyses because the number of R and L observations was not sufficient to perform the individual binomial tests. This resulted in the following sample sizes per motor function: n = 76 for snout, n = 60 for foot-up and foot down and n = 78 for tail curling
The pairwise comparisons revealed that the second replicate showed significantly weaker snout laterality compared to the fourth, t(71) = −3.78, p < .01, and the last, t(71) = −3.39, p < .01, replicates, while the third replicate showed significantly weaker snout laterality compared to the fourth replicate, t(71) = −3.13, p
Summary
Cerebral asymmetries are widespread in animals and are supposed to have an evolutionary advantage to improve brain efficiency by enabling the brain to LATERALITY: ASYMMETRIES OF BODY, BRAIN AND COGNITION perform more than one task simultaneously (Rogers, Zucca, & Vallortigara, 2004). Many species do not use their limbs for tasks of different complexity, such as walking and grabbing, which limits the testing of limb use in a variety of tasks For this reason, some authors adapted the “task complexity hypothesis” into the “organ complexity hypothesis” (Keerthipriya, Tewari, & Vidya, 2015), which suggests that the strength of lateralization varies between different organs. In food-reaching tasks, elephants are more strongly lateralized in the use of their trunk than their forefeet (Keerthipriya et al, 2015), and spider monkeys are more strongly lateralized in the use of their tail than their hands (Laska, 1998) From these conclusions, one can deduce that laterality varies across task and/or organ complexity. To get an overview of motor lateralization in a certain species, studies should ideally include different motor functions
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