Animal Laterality Research

Abstract

This chapter shifts gears from research with humans to animal research . It gives some findings for invertebrates and, through fossil evidence, indicates that lateralization processes were evident in the earliest life forms, well over 1 billion years ago. The chapter also examines laterality in extant species; the ubiquity of lateralization in species , such as bees, points to the evolutionary basis to the characteristic. The chapter also considers laterality in early hominins ; the evidence, for example, through tool use, also indicates an early presence of laterality in the lineage leading to modern humans . The best evidence in this regard concerns the study of lateralization in great apes/non-human primates, such as chimpanzees . Once methodological care is taken, these species also manifest a right-side lateralization for critical manual behaviors such as in the tube task and also in the wild. Even developing great apes/non-human primates exhibit this pattern. The evidence also indicates right hemispheric specialization in these species for its typical skills. At times, the evidence also reveals contradictory patterns of results related to great ape/non-human primate and human comparisons, including the brain areas involved (e.g., Broca) . As for evolutionary models on lateralization, some are very broad and refer to asymmetries stretching into the earliest species, while others focus on our more recent ancestry in the hominid line. The evidence does not uniquely support the primary hypotheses in the area, for example, a tool-use first or gestural communication first origin. Also, issue arises about the evolutionary continuity in lateralization and whether dextralization has arisen multiply and independently over the course of evolution. The chapter concludes on the relevance of the concept of activation-inhibition coordination as a common function in these different evolutionary models .