Summary

Experience can enhance, suppress or change in other ways the development of lateralization. Exactly which of these occurs depends on the species, the nature of the experience and the stage of life at which it takes place. Lateralization of individuals and groups can be modulated by experience and by steroid hormones. The latter may be important in the development of sex differences in lateralization. Research in this area is in its infancy compared with our knowledge of species differences in lateralization, but we are able to give some potent examples to illustrate the importance of experience and hormone levels at particular stages of development.

Introduction

The brain is not as hard-wired as once thought. It changes its connections in response to experience, especially in early life but also in adulthood. Some regions of the brain even change size in response to specific kinds of experience. The hippocampus is such a region. In humans, we know that the hippocampus has a special role in spatial memory. A study of London taxi drivers has shown that they have a larger than average posterior region of the right hippocampus and a smaller than average anterior region of the hippocampus (Maguire et al., 2000). In animals too, the size of the hippocampus is related to spatial ability. Species that cache food and retrieve it at a later time have a larger hippocampus than do closely related non-caching species. This is known to be the case in squirrels (Johnson et al., 2010), kangaroo rats (Jacobs and Spencer, 1994) and several species of birds, including marsh tits and Clarke’s nutcrackers (Shettleworth, 2003).