An epigenetic theory of hemispheric specialization: the role of prenatal sensori-motor experience in the development of turning bias and spatial orientation in bobwhite quail (Colinus virginianus)

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Virginia Tech


This study examined the effects of prenatal sensory and motor experience on the development of spatial orientation and turning bias in bobwhite quail. The theory presented here describes hemispheric specialization as the result of probabilistic events in the developing organism's prenatal environment; in particular, activity and experience in the final stages of prenatal development appear critical. Models and definitions of behavioral asymmetry, hemispheric specialization, and structural lateralization are reviewed. The results of Experiment 1 revealed a left-side turning bias in 85% of unmanipulated chicks. Experiments 2, 3, and 4 demonstrated that prenatal visual experience is a significant facilitator of population level left-side turning biases in bobwhite quail chicks. Experiment 5 investigated a potential underlying neurological basis for the bobwhite turning bias with unilateral injections of cycloheximide. The results of Experiment 5 suggest a left hemispheric specialization for the left-side turning bias. Furthermore, the results of Experiments 2 and 3 suggest that the asymmetrical hatching behaviors of the bobwhite quail are also a significant canalizing influence on the development of turning bias. The findings of this study are discussed in terms of an epigenetic theory of the development of hemispheric specialization and questions are raised as to the efficacy of laterality indexes as a reliable quantification of degree of hemispheric lateralization.



psychology, lateralization, prenatal, turning bias, quail