survival with an asymmetrical brain: advantages and disadvantages of cerebral lateralization

Abstract

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.

Factors Influencing the Prevalence and Handedness for Throwing in Captive Chimpanzees (Pan troglodytes).

“…The social role of throwing should not be minimized as a potentially important element to the emergence of left hemisphere specialization in motor skill and language. If throwing is conceived of as a social form of tool use, then it could be argued that neural recruitment and adaptation of lateralization for communication systems from existing motor systems involved in social contexts (i.e., throwing) would have been selected for rather than motor systems adapted for nonsocial functions, such as tool use associated solely with the procurement of food (see Vallortigara & Rogers, 2005). Four sequential frames demonstrating a chimpanzee throwing a polyvinyl chloride (PVC) pipe toward a human in a tower above the subject.…”

Embryonic exposure to predator odour modulates visual lateralization in cuttlefish

“…The strength of lateralization in laboratory-reared offspring is conserved between generations, consistent with it being a heritable character [11][12][13]. This may provide fitness benefits, both in terms of coordinated group antipredator responses and in terms of dual information processing [14]. Conversely, when females are collected from a high-predation pressure environment, the direction of lateralization is different between the wild-caught females and their laboratory-reared offspring [11].…”

Cerebral Asymmetry: A Quantitative, Multifactorial, and Plastic Brain Phenotype

“…Although acknowledged as a prominent feature of the organization of the brains of humans and other species (Vallortigara & Rogers, 2005), the biological mechanisms that underlie the establishment of normal brain lateralization and brain asymmetry remain largely to be discovered. Greater investigation in this field will be crucial not only to advance our knowledge of normal brain functioning, but it could also contribute to our understanding of neurodevelopmental and psychiatric diseases.…”