The book contains five separate studies that share a common theme involving the investigation of laterality in general, but ultimately describes new research on humans. It begins with a general introduction to concept of laterality. The topics covered include molecular asymmetries, laterality in plants and animals, and a section that specifically describes laterality in humans. This theoretical prologue is followed by five essays written in the style of scientific journal articles that can be read in sequence, or independently. Two of the studies focus on the investigation of laterality in Parkinson's disease. The first focuses on the relationship between the asymmetry of the initial motor symptoms of patients with Parkinson's disease and their pre-morbid handedness. The second considers the difference between the pre-morbid and current hand preferences of the patients. Two further studies attempt to answer more general questions regarding human laterality - how many handedness groups can be distinguished from population survey data and what are the predictors of human rotation. The remaining essay focuses on the level of measurement of the items used to measure handedness.