Right ear advantage for conspecific calls in adults and subadults, but not infants, California sea lions (Zalophus californianus): hemispheric specialization for communication?

This paper explores functional hemispheric asymmetries in the perception of auditory signals in a marine mammal species, the sea lion. Using a head-orienting task toward sounds we found a right ear--left hemisphere--advantage for conspecific calls in adult and subadult California sea lions (Zalophus californianus) that was absent in infants. Non-conspecific sounds did not elicit lateralized reactions in any age group. These findings show that maturational steps regarding communication in the brain of pinnipeds are similar to those described in primates. Such a result in a semi-aquatic species distant from primates on the phylogenetic tree speaks for a stability and an ancient emergence of the left hemispheric specialization for vocal communication. The origin of what seems to be a widespread brain feature might be searched in the temporal and spectral communicative sound's characteristics rather than in its semantic value.