"Summarizing the evidence and highlighting research from the past 20 years, the authors discuss lateralization from four perspectives - function, evolution, development, and causation - covering a wide range of animals including humans. The evolution of lateralization is traced from our earlier ancestors, through fish and reptiles to birds and mammals. The benefits of having a divided brain are discussed, as well as the influence of experience on its development. A final chapter discusses outstanding problems and areas for further investigation."