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M Annett

Publications and source records attributed to M Annett.

At least 37 records · Page 2Linked to original sources
PubMed1994

Handedness as a continuous variable with dextral shift: sex, generation, and family handedness in subgroups of left- and right-handers.

Percentages of left-handed relatives were compared between subgroups of left-handers and of right-handers to test the prediction that the subgroups are ordered for probability of carrying the rs +/gene (hypothesized by the right-shift theory of handedness). Data included families of undergraduates and Open University students who described their children as well as other relatives. Linear relationships were found between subgroup order and percentage of left-handed relatives. In agreement with previous evidence that some right-writers with weak sinistral preferences (class 2) are in fact more dextral than consistent right-handers (class 1), class 2 tended to have fewer left-handed relatives than class 1 in both samples. Left writers with weak dextral tendencies (class 7) tended to have more left-handed relatives that consistent left-handers (class 8). Comparisons of the distribution of subgroup handedness in undergraduates and their parents revealed strong effects for sex and for generation. In both cases, the main contrasts were not between left-handers and right-handers but between left-handers plus right-handers with weak dextrality and right-handers with strong dextrality. The findings are consistent with the theory that the relevant factor is not handedness as such but, rather, the absence or presence of the rs +/gene.

Adolescent↗
PubMed1994

Handedness as a function of twinning, age and sex.

Questions about twin birth, sex, age and handedness for writing were asked as part of a survey of hearing disability (Davis, 1989) in a large sample of the adult population. The findings show unequivocally that the prevalence of left handedness is higher in twins than in the singleborn, in males than in females and in younger than in older adults. There was a marked and regular decline in the percentage of left writers with increasing age, but the effects for twinning and sex were evident in all of 7 age bands from 18 years to 80+. The findings are consistent with the assumption of the right shift theory of handedness (Annett, 1972, 1985) that the rs+ gene is expressed more strongly in females than in males, and in the singleborn than in twins.

Adolescent↗
PubMed1994

Handedness and dyslexia: a meta-analysis.

The question whether there is an association between handedness and dyslexia has been investigated in many studies spanning more than 50 years. In 1990, Bishop reviewed studies which met stringent methodological criteria and concluded that there was little support for an association. A reanalysis of the same studies using newer procedures of meta-analysis shows that there is a small but reliable increase in the proportion of nonright-handers among dyslexics as expected by the right-shift theory of handedness of Annett.

Child↗
PubMed1993

The fallacy of the argument for reduced longevity in left-handers.

The fallacy of the argument for reduced longevity in left-handers depends on the use of the writing hand in the assessment of the present generation of elderly people, when writing was not used as a criterion in the early years of the century. A 'thought' experiment demonstrates that a sample of left-handers is likely to be younger than a sample of right-handers alive in the population and this would be true also of the recently deceased.

Adult↗
PubMed1992

Parallels between asymmetries of Planum temporale and of hand skill.

Relationships between the skill of each hand and differences between the hands are described for a sample of 14-15-year-olds representative of the general population. The description is modelled on the account of Galaburda et al. (Neuropsychologia 25, 853-868, 1987) of relationships between asymmetries of the Planum Temporale (PT) and measures of PT area on each side, in order to show parallels between findings for the two types of asymmetry. For both PT and hand skill, the extent of asymmetry appears to depend on the greater variability of the weaker side rather than of the larger or "better" side. The findings are also described as a replication of the study of hand skill in children by Annett and Manning (Br. J. Psychol. 80, 213-226, 1989). As no score transformations were needed in the present sample, the grounds for doubt raised by Bishop (Handedness and Developmental Disorder, Blackwell, Oxford, 1990) about the earlier sample are removed. Repetition of the analyses for right-handed and left-handed writers separately demonstrates very close similarities for findings in the two hand preference groups. Theories about the mechanisms responsible for asymmetries appear to require the presence of factors which reduce brain area and hand skill on one side. For most people the reduction is to the right PT and to the left hand.

Adolescent↗
PubMed1992

Five tests of hand skill.

Four group tests of hand skill, square marking (SQUARES), dotting between targets (DOTS), line drawing between targets (LINES) and punching holes through targets (HOLES), were given to samples of undergraduates and schoolchildren, most of whom were also tested individually on a peg moving task (PEGS). Findings for PEGS were shown to be comparable to those of previous samples. Each new task was compared with PEGS for a standard measure of hand skill asymmetry (R-L%) using 4 criteria of comparison. For 3 criteria there was good agreement: correlations were statistically significant, hand preference subgroups were similar for rank order and the extent of asymmetry was more strongly associated with left hand scores than with right hand scores. This last finding was true for all of 12 comparisons for differing tests and samples, indicating that the finding is unlikely to be an artefact of score transformations as suggested by Bishop (1990a, 1990b). The fourth criterion of comparison, the distribution of R-L% scores, differed between the tasks. All of the new tasks found larger differences between the hands than PEGS. Whereas the shape of the distribution was unimodal for PEGS, as in previous studies, the distributions for DOTS and HOLES were clearly bimodal. Possible reasons for the larger between hand differences for some tasks are considered. It is suggested that the main difference between PEGS (and also to a lesser extent LINES) in comparison with DOTS and HOLES lies in the demand characteristics of the testing situation. Tasks which merely invite subjects to mark as many targets as possible in a unit of time may underestimate the skill of the nonpreferred hand.

Adolescent↗
PubMed1992

Spatial ability in subgroups of left- and right-handers.

Two tests of spatial ability, mental paper folding given to 459 14-15-year-olds representative of the secondary school population, and recall of the Rey figure given to 428 undergraduates, found significant relationships between ability and hand preference when preferences were classified in subgroups of left- and right-handers (Annett, 1970a). In 14-15-year-olds and in female undergraduates there was a W-shaped relation between hand preference and spatial ability. The highest scores were in the centre for right-handers with strong sinistral tendencies. Male undergraduates showed a linear trend, with spatial ability highest in strong left-handers and declining from left to right across levels of hand preference. When spatial test scores were considered in relation to differences between the hands in skill a decline of ability with increasing dextrality was found in right-handers and in left-handers. In terms of the right shift theory (Annett, 1972, 1985), the evidence suggests that there are costs for spatial ability associated with the presence of the rs+ gene, even in single dose (rs+ - genotypes), and that those who lack the gene (rs- - genotypes) have advantages for spatial ability (Annett, 1991 c).

Adult↗
PubMed1991

Speech lateralisation and phonological skill.

A phoneme segmentation task requiring Ss to produce deliberate spoonerisms was performed by 78 undergraduates, along with a dichotic monitoring task and tests of hand preference and hand skill. The hypothesis that those performing badly on the speech task would include a higher proportion of individuals with left ear advantage on the dichotic task was supported. The distribution of cases was consistent with other findings for relationships between cerebral speech lateralisation and side of ear advantage and also consistent with predictions of the right shift theory of handedness and cerebral speech (Annett, 1972, 1985).

Adolescent↗
PubMed1991

Handedness for eating in gorillas.

Observations of spontaneous reaching for food in 31 captive lowland gorillas found a full range of hand preferences between strong left and strong right, with most animals showing intermediate levels of preference. There was a high degree of consistency between observations made on different occasions for the same animal, showing that degrees of relative preference tend to be stable in individuals. The findings agree with the majority of previous studies of apes and other primates in showing no species bias to one side, with about half the animals left and half right preferent.

Animals↗
PubMed1990

Arithmetic and laterality.

Relationships between arithmetic ability, hand preference and hand skill were investigated in a general population sample of schoolchildren, aged 9-11 years. Incidences of non-right-handedness were highest in the children best at arithmetic and fell progressively through average and below average groups. Strong effects were found for hand skill; level of ability declined linearly from left to right across the R-L continuum in both sexes. Strong dextrality was associated with poor left hand skill and not superior right hand skill. Arithmetic ability was positively associated with left hand skill but not with right hand skill.

Child↗
PubMed1990

Reading and a balanced polymorphism for laterality and ability.

The idea that reading ability might vary with right-left hand skill, such that children with mild biases to the right hand have advantages for learning, while children at both left and right extremes have disadvantages, was supported by findings for a large sample of primary schoolchildren. Poor readers tended to have weak left hand skills, giving strong right hand preferences in many cases. Those with additionally poor right hand skills tended to be of low intelligence. Good left hand skills and raised incidences of mixed and left hand preference were found only in a small subgroup, "bright dyslexics".

Aptitude↗
PubMed1989

The disadvantages of dextrality for intelligence.

The right shift (RS) theory of handedness suggests that the human bias to dextrality has costs as well as benefits. Samples of children from six primary schools were individually tested for hand preference, hand skill and Raven's Matrices. Scores on standardized educational tests recently given by teachers were available for three schools. When children were stratified for ability, the distributions of hand preference and of right minus left (R-L) hand skill were as expected if extent of RS is inversely related to ability. When children were classified for R-L score, the most strongly dextral children were poorer than all others for Matrices, English and several other tests. The trend for ability to decline from left to right across the laterality continuum was consistent for all scores available. Strong dextrality is associated with weak left-hand skill, not good right-hand skill, in accord with the hypothesis that the costs of RS are to the right hemisphere. The findings and their interpretation are discussed in comparison with Geschwind's theory of developmental pathology, and for their implications for theories of hemisphere specialization.

Cerebral Cortex↗
PubMed1988

Comments on Lindesay: laterality shift in homosexual men.

The raised incidences of strong left-handedness and of mixed-handedness in homosexual men, as in dyslexics, are mutually consistent under the normal distribution function, as expected by the right shift theory of handedness. It is argued that atypical laterality in these groups is better described as a "reduction of right shift" than as a "left shift".

Differential Threshold↗
PubMed1984

Lateral preference and skill in dyslexics: implications of the right shift theory.

The lateral preferences and L-R skill of 109 male and 20 female dyslexics were as expected if the distribution of lateral asymmetry is shifted less far to the right in dyslexics than in controls. Several aspects of the data were consistent with Annett's hypothesis that some dyslexics lack the left hemisphere speech-organising factor postulated by the right shift theory of handedness and that this would be sufficient to account for the proportion of affected relatives. Some dyslexics were strongly dextral and these differed from the less dextral cases in several ways which resembled the distinction between backward and retarded readers.

Child↗
PubMed1983

Individual variation in directional bias in visual perception.

Directional biases in visual perception were examined for individual differences in sixty-five subjects on two tasks. One task required judgments of the onset asynchrony of pairs of dots presented at random, either one dot in each visual field, or both in the left visual field (LVF), or the right visual field (RVF). The second task required the recall of four letter strings presented randomly in either visual field. Dot-asynchrony judgments were influenced by two main biases: first, an outward from the centre bias in both visual fields, and second, a lateral bias which was significantly from left to right (L-R) in the total sample. A substantial minority of subjects were biased to judge the dots as occurring in right to left (R-L) order. Accuracy of letter report decreased fairly consistently from L-R in the RVF but varied in the LVF. Some subjects showed a L-R report gradient, some a R-L gradient, and some a U-shaped recall pattern. Significant correlations between measures of L-R and R-L biases on the two tasks show that the biases have some stable foundation. The findings suggest that there are directional biases affecting visual perception which are due neither to learned reading habits, nor to cerebral specialization of function.

Female↗
PubMed1983

Right- and left-hand skill I: Effects of age, sex and hand preference showing superior skill in left-handers.

Hand preference and hand skill were examined in relation to sex and age from 3 1/2 to 50+ years. The data were drawn from several samples which avoided volunteer bias, either by selecting children according to birth-date or by taking complete class groups. The distribution of hand preference and of asymmetry of skill gave no evidence of systematic changes with age. Younger children were more variable and showed larger absolute differences in favour of the right hand than older children but L-R times were similar over most of the age range. Time for peg moving decreased with increasing age to a minimum in the late teens, remained stable for the next three decades and increased slightly in the 50+ age group. Males were faster than females with the left hand in almost all age groups. Females tended to be faster than males with the right hand up to 10 years of age but males then equalled and surpassed females, to be faster in most older groups. Correlations between hands did not vary systematically with age or sex. Left-handers were faster than right-handers and right mixed-handers were intermediate for peg-moving time by the non-preferred hand, in both sexes and both sets of samples. Differences for the preferred hand were less clear but still favoured left-handers in several comparisons. The findings raise the possibility that left hemisphere specialization for language is achieved through a right hemisphere handicap and that left-handers escape this risk to cerebral efficiency.

Adolescent↗