In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more dextrous. The other hand, comparatively often the weaker, less dextrous or simply less subjectively preferred, is called the non-dominant hand. In a study from 1975 on 7,688 children in US grades 1-6, Left handers comprised 9.6% of the sample, with 10.5% of male children and 8.7% of female children being left-handed. Handedness is often defined by one's writing hand, as it is fairly common for people to prefer to do a particular task with a particular hand. There are true ambidexterity, but it is rare—most people prefer using one hand for most purposes.
Stevan Robert Harnad is a Hungarian-born cognitive scientist based in Montreal, Canada.
A gesture is a form of non-verbal communication or non-vocal communication in which visible bodily actions communicate particular messages, either in place of, or in conjunction with, speech. Gestures include movement of the hands, face, or other parts of the body. Gestures differ from physical non-verbal communication that does not communicate specific messages, such as purely expressive displays, proxemics, or displays of joint attention. Gestures allow individuals to communicate a variety of feelings and thoughts, from contempt and hostility to approval and affection, often together with body language in addition to words when they speak. Gesticulation and speech work independently of each other, but join to provide emphasis and meaning.
Split-brain or callosal syndrome is a type of disconnection syndrome when the corpus callosum connecting the two hemispheres of the brain is severed to some degree. It is an association of symptoms produced by disruption of, or interference with, the connection between the hemispheres of the brain. The surgical operation to produce this condition involves transection of the corpus callosum, and is usually a last resort to treat refractory epilepsy. Initially, partial callosotomies are performed; if this operation does not succeed, a complete callosotomy is performed to mitigate the risk of accidental physical injury by reducing the severity and violence of epileptic seizures. Before using callosotomies, epilepsy is instead treated through pharmaceutical means. After surgery, neuropsychological assessments are often performed.
The term laterality refers to the preference most humans show for one side of their body over the other. Examples include left-handedness/right-handedness and left/right-footedness; it may also refer to the primary use of the left or right hemisphere in the brain. It may also apply to animals or plants. The majority of tests have been conducted on humans, specifically to determine the effects on language.
The planum temporale is the cortical area just posterior to the auditory cortex within the Sylvian fissure. It is a triangular region which forms the heart of Wernicke's area, one of the most important functional areas for language. Original studies on this area found that the planum temporale was one of the most asymmetric regions in the brain, with this area being up to ten times larger in the left cerebral hemisphere than the right.
Michael S. Gazzaniga is a professor of psychology at the University of California, Santa Barbara in the USA, where he heads the new SAGE Center for the Study of the Mind. He is one of the leading researchers in cognitive neuroscience, the study of the neural basis of mind. He is a member of the American Academy of Arts & Sciences, the Institute of Medicine, and the National Academy of Sciences.
Stanley Albert Gooch was a British psychologist and author who is probably best known as the proponent of a "hybrid-origin theory" of human evolution.
A commissurotomy is a surgical incision of a commissure in the body, as one made in the heart at the edges of the commissure formed by cardiac valves, or one made in the brain to treat certain psychiatric disorders.
Doreen Kimura was a Canadian psychologist who was professor at the University of Western Ontario and professor emeritus at Simon Fraser University. Kimura was recognized for her contributions to the field of neuropsychology and later, her advocacy for academic freedom. She was the founding president of the Society for Academic Freedom and Scholarship.
The Geschwind–Galaburda hypothesis is a neurological theory proposed by Norman Geschwind and Albert Galaburda in 1987. The hypothesis posits there are sex differences in cognitive abilities by relating them to lateralisation of brain function. The maturation rates of cerebral hemispheres differ and are mediated by circuiting testosterone levels, which are substantially influenced during the foetal and post-puberty development stages.
Richard J. Davidson is a professor of psychology and psychiatry at the University of Wisconsin–Madison as well as founder and chair of the Center for Healthy Minds and the affiliated non-profit Healthy Minds Innovations.
A relationship between handedness and sexual orientation has been suggested by a number of researchers, who report that heterosexual individuals are somewhat more likely to be right-handed than are homosexual individuals.
In human neuroanatomy, brain asymmetry can refer to at least two quite distinct findings:
Emotional lateralization is the asymmetrical representation of emotional control and processing in the brain. There is evidence for the lateralization of other brain functions as well.
Dichotic listening is a psychological test commonly used to investigate selective attention and the lateralization of brain function within the auditory system. It is used within the fields of cognitive psychology and neuroscience.
The left-brain interpreter is a neuropsychological concept developed by the psychologist Michael S. Gazzaniga and the neuroscientist Joseph E. LeDoux. It refers to the construction of explanations by the left brain hemisphere in order to make sense of the world by reconciling new information with what was known before. The left-brain interpreter attempts to rationalize, reason and generalize new information it receives in order to relate the past to the present.
Michael Charles Corballis was a New Zealand and Canadian psychologist and author. He was Emeritus Professor at the Department of Psychology at the University of Auckland. His fields of research were cognitive psychology and cognitive neuroscience, encompassing visual perception, visual imagery, attention, memory, and the evolution of language.
Mike Nicholls is an Australian researcher in experimental psychology.
Sabine Kastner is a German-born American cognitive neuroscientist. She is professor of psychology at the Princeton Neuroscience Institute at Princeton University. She also holds a visiting scientist appointment at the University of California at Berkeley.
