Research on lateralization of brain and behaviour in animals has expanded rapidly over the past two decades and continues to grow exponentially. The same is true of studies on lateralization in humans, and the evidence from these two sources is integrated in this book in a way not previously attempted. We were motivated to write this book because of the widening interest in the subject and a perceived need to make the most up-to-date information available in a form that, we hope, is stimulating and easy to read. Since there are many general texts on cerebral specialization in humans, our chief focus was on left–right differences in brain and behaviour in non-human animals, with the aim of bringing together recent striking advances arising from study of lateralization in these species and the state of knowledge of lateralization in humans.

We approached the topic of lateralization from the perspective of Tinbergen’s four questions (function, evolution, development, causation), to each of which we have devoted one chapter.