Survival with asymmetrical brain: advantages and disadvantages of cerebral lateralization. Behav Brain Sci

Department of Psychology and B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34123 Trieste, Italy.
Behavioral and Brain Sciences (Impact Factor: 20.77). 09/2005; 28(4):575-89; discussion 589-633. DOI: 10.1017/S0140525X05000105
Source: PubMed


Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an "evolutionarily stable strategy" under "social" pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.

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    • "Since in our case the asymmetry is found in skull bones, it may also affect feeding behaviour. Such asymmetrical behaviour is probably related to brain asymmetry, which is known to affect behaviour of not only higher, but also low vertebrates (Malashichev and Wassersug, 2004; Vallortigara and Rogers, 2005; Izvekov et al., 2014). We also found that directional asymmetry of one character is associated with differences in pollution. "
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    • "Laterality is defined as a bias for one side of the body over the other. Once thought to be unique to humans, lateralization is a pervasive pattern in both vertebrate and invertebrate brain and behavior [for reviews, see Frasnelli et al., 2012; Frasnelli, 2013; Rogers et al., 2013; Vallortigara & Rogers, 2005]. "
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    • "Earlier findings by Marchant-Forde and Marchant-Forde (2014) suggest that the left-eye staining may be a more sensitive welfare indicator. Cerebral lateralization may be the cause behind this, as it has been shown that animals may be more reactive to threats approaching within the left-eye visual field (Vallortigara and Rogers, 2005), but the physiological mechanisms of the potential asymmetry of tear staining are as yet unknown. "
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