Crossed dominance and its relationship to intelligence and academic achievement

Is crossed laterality associated with academic achievement and intelligence? A systematic review and meta-analysis

Over the last century, sporadic research has suggested that people whose hand, eye, foot, or ear dominances are not consistently right- or left-sided are at special risk of suffering academic difficulties. This phenomenon is known as crossed laterality. Although the bulk of this research dates from 1960's and 1970's, crossed laterality is becoming increasingly popular in the area of school education, driving the creation of several interventions aimed at restoring or consolidating lateral dominance. However, the available evidence is fragmentary. To determine the impact of crossed laterality on academic achievement and intelligence, we conducted a systematic review and meta-analysis of articles published since 1900. The inclusion criteria for the review required that studies used one or more lateral preference tasks for at least two specific parts of the body; they included a valid measure of crossed laterality; they measured the impact of crossed laterality on academic achievement or intelligence; and they included participants between 3 and 17 years old. The final sample included 26 articles that covered a total population of 3578 children aged 5 to 12. Taken collectively, the results of these studies do not support the claim that there is a reliable association between crossed laterality and either academic achievement or intelligence. Along with this, we detected important shortcomings in the literature, such as considerable heterogeneity among the variables used to measure laterality and among the tasks utilized to measure the outcomes. The educational implications of these results are discussed.

Is left-handedness associated with a more pronounced age-related cognitive decline?

The effect of handedness on cognitive functioning has been the subject of much controversy. The influential "pathological left-handedness theory" posited by Coren and Halpern (1991) claims that left-handedness is probabilistically related to deviations from the neurological and cognitive norm. Many studies have failed to find negative effects of left-handedness on cognitive functioning, but most of these studies related handedness to cognition at one moment in time. Such studies do not exclude the possibility that sinistrality may be related to a more pronounced age-related longitudinal decline in cognitive functions. This hypothesis was tested in the present study. In a longitudinal study involving a large population sample of cognitively intact people aged at least 50 years at baseline, we evaluated the effect of handedness on age-related decline in four major cognitive domains: speed of information processing, verbal learning, long-term verbal memory, and executive functioning. The results failed to provide support for the hypothesis that sinistrality is associated with a more pronounced age-related cognitive decline. Recommendations for future studies are provided.

Perceptual visual skills in young highly skilled basketball players

A simple method was designed to evaluate visual abilities such as disance visual acuity, binocular horizontal visual field, simple and choice visual reaction times, and stereoscopic vision in skilled 11- to 13-yr.-old basketball players participating in a 15-day summer training camp. On a test battery, visual abilities were monitored in 473 players of the Spanish Basketball Federation over a 5-yr. period. The players showed outstanding scores on distance visual acuity and stereoscopic vision, and good visual reaction times and horizontal visual fields. When scores were compared by sex and age, significant differences on certain visual measures were observed. Many layers showed crossed eye-hand dominance. Visual screening programs may help promote visual health among junior basketball players and could be used for performance training.

Left-handedness and achievements in foreign language studies

Studies of brain lateralization lend support to the hypothesis that language-motor functions in left-handers are differently organized from those in right-handers. However, the implications of these differences regarding cognitive functioning are as yet subject to controversy. This concerns all hypotheses raised and empirical data collected over the years. Although it was suggested that left-handers are at higher risk of having language and reading deficits, empirical data from clinical and nonclinical populations are inconclusive at the present time. No effort, however, has been invested in examining possible differences in academic studies of foreign languages according to handedness. Here we report data indicating inferior achievements of left-handed native Hebrew speakers in studies of English as a foreign language. Left-handed pupils significantly more than right-handers were placed in lower level English classes and had more difficulties in applying orthographic-phonological mapping rules in reading English words and pseudowords. However, left-handers' difficulties in this task were not correlated with their performance in a word recognition task. It is thus suggested that the "common symptom" of poor word reading in left-handers indicates different processing failures in different left-handers, some of which impede the buildup of an internal representational system of mapping orthography to phonology and some of which concern mainly the precision of word production.