Researchers have suggested a link between handedness and ability with mathematics . This link has been proposed by Geschwind, Galaburda, Annett, and Kilshaw. The suggested link is that a brain without extreme bias towards locating language in the left hemisphere would have an advantage in mathematical ability. [1]
A 1967 study by Douglas found no evidence to correlate mathematical ability with left-handedness or ambidexterity. The study compared the people who came in the top 15% of a mathematics examination with those of moderate mathematical ability, and found that the two groups' handedness preferences were similar. However, it did find that those who came lowest in the test had mixed hand preferences. A study in 1979 by Peterson found a trend towards low rates of left-handedness in science students. [1]
A 1980 study by Jones and Bell also obtained negative results. This study compared the handedness of a group of engineering students with strong mathematics skills against the handedness of a group of psychology students (of varying mathematics skills). In both cases, the distribution of handedness resembled that of the general population. [1]
Annett and Kilshaw themselves support their hypothesis with several examples, including a handedness questionnaire given to undergraduates. Annett observes that studies that depend from voluntary returns of a handedness questionnaire are going to be biased towards left-handedness, and notes that this was a weakness of the study. However, the results were that there were significantly more left-handers amongst male mathematics undergraduates than male non-mathematics undergraduates (21% versus 11%) and significantly more non-right-handers (44% versus 24%), and that there was a similar but smaller left-handedness difference for female undergraduates (11% versus 8%). Annett reports the results of this study as being consistent with the hypothesis, for explaining the cause of handedness, of an absent genetic right-shift factor. [1] [2]
Other examples used by Annett include a study that observed the hand use of teachers of mathematics and other sciences from various universities and polytechnics, as they underwent a personal interview, compared to a control group comprising non-mathematics teachers. Again, a statistically significant difference was found for males, and again Annett states this to be consistent with the right-shift model. Further examples are a 1986 study by Benbow and a 1990 study by Temple of staff at the University of Oxford, which, Annett states, show not that there is a predominance of left-handers in talented groups, whether that talent be with mathematics or otherwise, but rather that there is a shortfall in such groups of people who are strongly right-handed. [2]
A study by C. P. Benbow did not work to prove the mathematical abilities of study participants who are left-hand dominant but to prove the weakness in those who are right-hand dominant. Using a series of questions that relate left-handedness and mathematical giftedness, Benbow was able to base their team's conclusion off of a series of questions that associated hand dominance and mathematical ability. [3]
As a controversial subject, the debate over the link between handedness and mathematical abilities is ongoing. Researchers at the University of Liverpool concluded that there is a moderate, yet significant correlation between mathematical skills and handedness. [4]
The relationship between biology and sexual orientation is a subject of on-going research. While scientists do not know the exact cause of sexual orientation, they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences. However, evidence is weak for hypotheses that the post-natal social environment impacts sexual orientation, especially for males.
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. Overall, around 90% of people are right-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 people with true ambidexterity, but it is rare—most people prefer using one hand for most purposes.
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.
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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 fields such as epidemiology, social sciences, psychology and statistics, an observational study draws inferences from a sample to a population where the independent variable is not under the control of the researcher because of ethical concerns or logistical constraints. One common observational study is about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator. This is in contrast with experiments, such as randomized controlled trials, where each subject is randomly assigned to a treated group or a control group. Observational studies, for lacking an assignment mechanism, naturally present difficulties for inferential analysis.
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The Edinburgh Handedness Inventory is a measurement scale used to assess the dominance of a person's right or left hand in everyday activities, sometimes referred to as laterality. The inventory can be used by an observer assessing the person, or by a person self-reporting hand use. The latter method tends to be less reliable due to a person over-attributing tasks to the dominant hand.
Camilla Persson Benbow is a Swedish-born (Scania) American educational psychologist and a university professor. She studies the education of intellectually gifted students.
Non-verbal leakage is a form of non-verbal behavior that occurs when a person verbalizes one thing, but their body language indicates another, common forms of which include facial movements and hand-to-face gestures. The term "non-verbal leakage" got its origin in literature in 1968, leading to many subsequent studies on the topic throughout the 1970s, with related studies continuing today.
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Bias against left-handed people is bias or design that is usually unfavorable against people who are left-handed. Handwriting is one of the biggest sources of disadvantage for left-handed people, other than for those forced to work with certain machinery. About 90 percent of the world's population is right-handed, and many common articles are designed for efficient use by right-handed people, and may be inconvenient, painful, or even dangerous for left-handed people to use. These may include school desks, kitchen implements, and tools ranging from simple scissors to hazardous machinery such as power saws.
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An estimated 90% of the world's human population consider themselves to be right-handed. The human brain's control of motor function is a mirror image in terms of connectivity; the left hemisphere controls the right hand and vice versa. This theoretically means that the hemisphere contralateral to the dominant hand tends to be more dominant than the ipsilateral hemisphere, however this is not always the case and there are numerous other factors which contribute in complex ways to physical hand preference.