laterality
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What does laterality mean in the human body?
In biological psychology, laterality refers to the development of specialized functions in each hemisphere of the brain, or in the side of the body that each hemisphere controls.
Handedness is the most noticeable example of laterality, shown by the tendency to use one hand more than the other for different activities. People are generally classified as right-handed, left-handed, or ambidextrous. Ambidexterity is the ability to use both the right and left hands with equal ease.
The origin of handedness is still debated. Some researchers suggest it is genetic, while others believe it is due to environmental factors. It is believed that most children can be trained to prefer their right hand without any harmful effects.
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Why are some people right-handed and others left-handed?
Laterality, a characteristic of the human brain, explains why some people are right-handed and others are left-handed. It refers to the specialized functioning of each hemisphere of the brain or the side of the body that each controls.
The origin of handedness is still debated. Some experts believe that laterality is inherited, while others think that a child is trained to it. Still others suggest that biases are initiated in an infant during pregnancy. It is possible that all three hypotheses are correct to some extent.
Most children are right-handed, but left-handed parents are more likely to have left-handed offspring than right-handed parents. There is data suggesting that humans are genetically biased toward right-handedness.
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How does the brain control different sides of the body?
Each cerebral hemisphere controls the opposite side of the body; the left hemisphere manages the right side, and the right hemisphere controls the left side. This contralateral control arises because the corticospinal tracts, which extend from the brain to the spinal cord, cross over in the brainstem. Therefore, damage to one hemisphere typically results in paralysis or weakness on the opposite side of the body.
The corpus callosum facilitates communication between the two hemispheres, allowing them to coordinate and integrate sensory and motor information. Despite their interconnectedness, the hemispheres aren't functionally equal; one hemisphere is typically dominant, controlling language, handedness, and analytical functions, while the non-dominant hemisphere handles spatial concepts, facial recognition, and emotional processing.
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What are examples of laterality besides handedness?
Laterality refers to the specialized functioning of each brain hemisphere or the side of the body that each controls.
Besides handedness, examples of laterality include how the left hemisphere is dominant for language in most people, while the right hemisphere is specialized for visual perception, spatial orientation, and recognizing objects and faces. Footedness, the preference for using one foot over the other, and eye dominance, the tendency to prefer visual input from one eye, are also examples of laterality.
The origins of handedness and other forms of laterality are still debated, with some researchers suggesting a genetic origin, while others propose environmental factors.
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How can laterality affect how we learn or do activities?
The idea that people are distinctly "left-brained" or "right-brained" is a misconception. Though the brain's hemispheres do specialize in certain functions, this division is more intricate than the notion of creativity residing solely on the right and logic on the left.
Laterality refers to the specialized functioning of each brain hemisphere or the side of the body that each controls. The most evident example of laterality is handedness, which is the preference for using one hand over the other for activities. People are generally classified as right-handed, left-handed, or ambidextrous.
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What are some psychological theories or studies about why laterality exists in humans?
Laterality in humans refers to the specialized functioning of each brain hemisphere or the side of the body that each controls. Handedness, the tendency to favor one hand for activities, is the most noticeable example.
Several theories attempt to explain the origin of manual preferences. Some propose that laterality is inherited, while others believe it results from training. A further hypothesis suggests that intrauterine forces or extrauterine environmental influences during pregnancy initiate biases in an infant.
One theory suggests that language is represented in a single hemisphere to prevent competition between hemispheres for speech muscle control. Another theory posits that representing the language system in a restricted area on one side of the brain is more efficient due to shorter information transfer distances and fewer connections. Some data indicates a genetic bias toward right-handedness in humans.
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laterality, in biological psychology, the development of specialized functioning in each hemisphere of the brain or in the side of the body which each controls.
The most obvious example of laterality is handedness, which is the tendency to use one hand or the other to perform activities. It is the usual practice to classify persons as right-handed, left-handed, or ambidextrous (two-handed). People differ considerably in the range of activities for which they prefer a given hand as well as in the degree of disparity in skill between their two hands. Probably no one favours either the right or left hand exclusively.
Origin and development
There is no extensive agreement on the origin of manual preferences. Some believe such laterality is inherited; others, that the child is trained to it; and still others, that biases are initiated in an infant during pregnancy by some organization of intrauterine forces, such as those producing twinning, or some extrauterine environmental influences. It is possible all three hypotheses are, in some measure, correct. It does seem clear that left-handed parents more frequently have left-handed offspring than do right-handed parents; that even at birth most babies tend to move one arm—usually the right—more than the other; and that, if a systematic effort is made to keep infants from developing a preference, they still come to favour one hand. It is equally apparent that most babies shift their preference once or twice during their first year. The consistency with which children use one hand in preference to the other increases with age, at least through the preschool years and probably longer. By far, most children are right-handed.
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There is some data suggesting that humans are genetically biased toward right-handedness. During the third and fourth months of gestation, for example, a fetus’ fingerprints are larger on the right hand than the left. Recent research, however, suggests that right-handedness and left-handedness are not genetically encoded within the body’s genes but rather are coded in the spatial structure of ovarian cells. Other scientists believe handedness is not biologically determined at all, but is a factor of the environment. Most children can be trained to use and to prefer the right hand for any activity, and many have been so trained without obvious harmful effects. The wisdom of interfering with a child’s spontaneous preference, however, has been questioned.
Laterality in the body
One of the first to suggest the relationship between the brain’s hemispheres and specialized functions was the French pathologist and anthropologist Paul Broca (1824–80). He localized the brain centre for articulate speech in the third convolution of the left frontal lobe. He referred to this area as the “convolution of Broca” (mainly known as Broca’s area). Broca also realized that damage to the brain’s left hemisphere could lead to the loss of certain abilities such as the comprehension of spoken language and such functions as speech, reading, and writing. Loss of these functions is referred to as aphasia, alexia, and agraphia, respectively. Broca’s work seems supported by evidence that the brain speech centre tends to be located in the hemisphere (usually left) opposite to the side of the dominant hand (usually right) and that brain waves from corresponding parts of the two cerebral hemispheres are more conspicuous on the nondominant side. This evidence, however, fails to prove that the cortical organization a person inherits is responsible for his hand preference. There is little support for the view, as the theory of a dominant cerebral hemisphere might lead one to expect, that the body structures under the control of one hemisphere are uniformly more efficient than those under control of the other. Indeed, the dominant hand is not always on the side of the dominant foot, and about three-fourths of right-handed and one-third of left-handed persons are right-eyed in sighting.