A general theory concerning the prenatal origins of cerebral lateralization in humans.

Abstract

The origins of cerebral lateralization in humans are traced to the asymmetric prenatal development of the ear and labyrinth. Aural lateralization is hypothesized to result from an asymmetry in craniofacial development, whereas vestibular dominance is traced to the position of the fetus during the final trimester. A right-ear sensitivity advantage may contribute to a left-hemispheric advantage in speech perception and language functions, whereas left-otolithic dominance may independently promote right-sided motoric dominance and a right-hemispheric superiority in most visuospatial functions. The emergence of handedness is linked to the assumption of an upright posture in the early hominids, whereas the failure to develop clear vestibular asymmetry may underlie the poor motoric lateralization found in several neurodevelopmental disorders.

Heritability of hand preference in chimpanzees (Pan troglodytes): Evidence from a partial interspecies cross-fostering study.

“…One possible mechanism is the position of the infant in utero and its effect on postural and head-orienting behavior of the off-spring. Regarding the intrauterine environment, Previc (1991) proposed that during the last trimester, the fetus is oriented such that its head is projected outward, which places constraints on the movements of the left hand of the fetus because of its proximity to the mother's pelvis and back-bone. From this position, the fetus receives different stimulation of the right otolith compared with the left because of asymmetries in acceleration and deceleration forces associated with bipedal walking by the mother.…”

Lateral asymmetries in infant melody perception.

“…Could pitch differences account for the observed pattern of lateralization? Previc ( 1991 ) suggested that many results indicating left-or right-ear advantages could be explained by differences in absolute frequency, with left-ear advantages for high frequencies (although he was referring to frequencies > 1000 Hz). In a different type of task, righthanded adults showed lateral asymmetries for relative pitch frequency, with a right-ear advantage when target stimuli were relatively higher in pitch compared to the average stimulus presented, and a-left-ear advantage for relatively lower pitch targets (Ivry & Lebby, 1993).…”

Estudo da vantagem da orelha direita em teste de detecção de gap

“…Furthermore, 95% of right-handed and 70% of left-handed individuals have left hemispheric language specialization. 39 If the sample contained individuals with right hemispheric specialization, they would not be sufficient to contaminate the results.…”