ABSTRACT
Human handedness has been the subject of systematic study since 1646, but there is no agreement among researchers as to who can be considered a left-hander, what is the etiology of left-handedness, or what the proportion of left-handedness is in the world's population. This article reports the results of a handedness survey administered to 12,000 subjects in 17 countries, the largest handedness survey attempted. The paper discusses methods for determining handedness, the probability of a genetic component for handedness, and the relationship of sex, birth order, multiple birth, and first-degree relative's handedness on subject's handedness. A hypothesis for the etiology of left-handedness is presented.
Subject(s)
Cross-Cultural Comparison , Functional Laterality/genetics , Adult , Aged , Female , Genetics, Population , Humans , Male , Middle Aged , Sex Factors , Twins/geneticsABSTRACT
Experimental data, primarily from experiments with Drosophila, and observational data, primarily from human beings, are presented to show if their is a genetic basis for laterality. The evidence was found to be inconclusive. It is proposed that there for three etiologies of lefthandedness in human beings: pathological, natural, and learned.
Subject(s)
Functional Laterality , Phenotype , Animals , Drosophila melanogaster , Female , Humans , Male , Sex FactorsSubject(s)
Functional Laterality/physiology , Adult , Child , Child, Preschool , Cognition Disorders/epidemiology , Dominance, Cerebral , Female , Fetal Hypoxia/complications , Handwriting , Humans , Intellectual Disability/epidemiology , Intelligence , Male , Perception/physiology , Pregnancy , Twins, MonozygoticABSTRACT
This study investigated sex differences in attention to verbal stimuli presented in auditory and visual modes. Ss were 996 male and female students, ages 7 through 17, who observed different forms of a sound motion picture film. One control film contained auditory verbal stimuli only, the other control film contained visual verbal stimuli only, and the experimental film contained simultaneous, conflicting auditory and visual verbal stimuli. Attending behavior was quantified as the number of stimulus specific answers on a paper-and-pencil test administered after presentation of the film. Prior results had indicated that experimental Ss under the age of 12 attended auditory stimuli significantly more often, and those over the age of 13 attended visual stimuli significantly more often. The present experiment concerned sex differences in attending behavior during the crossover period: it was found that females switched their preference for auditory stimuli to visual stimuli earlier (age 11.5) than males (age 13.5). The significant differences between sexes (p less than .05) were attributed to differential conditioning of attitudes, reinforcements, and discriminations regarding the stimulus presentation mode, as well as biological factors.
