Lateral preferences are strange, puzzling, and on the surface, not particularly adaptive aspects of behavior. Why one chooses habitually to write or to brush the teeth with the right hand, while a friend or family member habitually uses the left hand, might be interesting enough to elicit some conversation over dinner or a drink, but certainly does not seem to warrant serious scientific study. Yet when one looks at human behaviors more carefully, one becomes aware that asymmet rical behaviors favoring one side or the other are actually a fairly universal characteristic of human beings. In the same way that we are right or left handed, we are also right or left footed, eyed, and eared. As a species, we are quite lopsided in our behavioral coordinations; furthermore, the vast majority of us are right sided. Considering that we are looking at a sizable number of behaviors, and at a set of biases that seem to be systematic and show a predictable skew in the popUlation, the problem takes on greater significance. The most obvious form of lateral preference is, of course, handedness. When studying behavioral asymmetries, this is the issue with which most investigators start. Actually, we entered this research area through a much different route. Around 1971 we became interested in the problem of eye dominance or eye preference. This is a behavior where the input to one eye seems to be preferred over that to the other in certain binocular viewing situations.

Left-handedness has been connected to many different conditions, traits, and abilities. This is especially true for pathological syndromes, such as schizophrenia, along with learning disabilities and autism. The published research on handedness is vast and frequently contradictory, often raising more questions than providing answers. Questions such as: - Is handedness genetic? - Can handedness be changed? - Are there consequences to training someone to switch handedness? - Are there positive traits associated with left-handedness like creativity? - Are there negative traits associated with left-handedness like trouble reading maps? - Is it abnormal to do some things right-handed and other things left-handed? - Are the brains of left-handers different from the brains of right-handers? Laterality: Exploring the Enigma of Left-Handedness examines the research conducted over the past 50 years with special emphasis on twenty-first century research on handedness and translates this literature into an accessible and readable form. Each chapter is based on a question or questions covering diverse topics such as genetic and biological origins of handedness, familial and hormonal influences on handedness, and the effects of a majority right-handed world on the behaviors of left-handers. - Summarizes scientific research on laterality - Separates fact from fiction in common beliefs about laterality - Includes illustrative interviews with left-handers

Twins present special problems for the study of lateralisation, both psychological and biological. Central to both areas is the common observation that identical (monozygotic) twins can differ in their laterality. In the case of hand preference, this is most obvious in the one in five twin pairs where one is right-handed and the other left-handed. A similar problem can be found morphologically, not only in normal anatomical traits, such as hair whorls, which can be in opposite direction, but also in the rare condition of conjoined twins, where it is frequently the case that one twin has its heart and viscera in the normal orientation (situs solitus) and the other is mirror reversed (situs inversus). This special issue of Laterality brings together papers on these different aspects of twinning. Two of the papers are biological, one providing a detailed analysis of the laterality of artificially conjoined twins created by fusing two different species of newt, and the other overviewing the recent developments in understanding the molecular biology of visceral lateralisation in relation to twinning. The other papers concern aspects of cerebral lateralisation in twins, one providing a much needed meta-analysis and critical overview of the twin literature, another providing detailed data from a large study of handedness in twins, a third asking about the almost neglected question of footedness, earedness and eyedness in twins, and the fourth looking at lateralised cognitive processing. Between them these papers extend the literature on lateralisation in twins, and reinforce the need to consider the lateralisation of twins from biological, neurological and psychological perspectives.

Left-handedness has been shown to be a possible marker for various psychological and physical abnormalities. This book presents evidence by a number of researchers who evaluate whether there are indeed differences between left- and right-handers which extend into the broader psychological and physiological realms.Several chapters show that left-handedness is found in unexpectedly high proportions in populations that suffer from various immune deficiency diseases, in alcoholics, dyslexics, mental retardates, psychopaths and other clinical groups. The book indicates why left-handedness should be a marker for such conditions. The genetic and environmental pressures on handedness are explored. A model for pathological left-handedness is presented, along with some interesting data which suggests that left-handedness may be associated with reduced life-span. Finally, several chapters discuss the implications of handedness patterns in non-clinical populations.

A collection of foundational texts on the nature and behavioral consequences of sex differences in the brain, allowing readers to follow the development of a rapidly growing but contentious field and giving them the tools to analyze emerging scientific findings from many perspectives. This collection of foundational papers on sex differences in the brain traces the development of a much-invoked, fast-growing young field at the intersection of brain and behavior. The reader is introduced to the meaning and nature of sexual dimorphisms, the mechanisms and consequences of steroid hormone action, and the impact of the field on interpretations of sexuality and gender. Building on each other in point-counterpoint fashion, the papers tell a fascinating story of an emerging science working out its core assumptions. Experimental and theoretical papers, woven together by editor's introductions, open a window onto knowledge in the making and a vigorous debate between reductionist and pluralist interpreters. Five major sections include papers on conceptual and methodological background, central nervous system dimorphisms, mechanisms for creating dimorphisms, dimorphisms and cognition, and dimorphisms and identity. Each section builds from basic concepts to early experiments, from experimental models to humans, and from molecules to mind. Papers by such leading scholars as Arthur Arnold, Frank Beach, Anne Fausto-Sterling, Patricia Goldman-Rakic, Doreen Kimura, Simon LeVay, Bruce McEwen, Michael Merzenich, Bertram O'Malley, Geoffrey Raisman, and Dick Swaab, illustrate a rich blend of perspectives, approaches, methods, and findings. Sex and the Brain will show students how a scientific paper can be analyzed from many perspectives, and supply them with critical tools for judging a rapidly emerging science in a contentious area.

`Rather than being an esoteric aspect of brain function, lateralization is a fundamental characteristic of the vertebrate brain essential to a broad range of neural and behavioral processes.' Professor Lesley J. Rogers, Chapter 1 of Side Bias: A Neuropsychological Perspective. This volume contains 14 chapters from a veritable `United Nations' of experts in the field of lateralization of function. They write comprehensive reviews, present data, and pose new questions concerning the evolutionary origins and development of side bias, methodological concerns with the way we measure handedness and footedness, and some more unusual aspects of human beings' lateralized behavior, such as asymmetrical cradling and pseudoneglect. The book will be essential reading for students of behavioral neuroscience and neuropsychology interested in lateralization of function as well as for established researchers in the field.