The Effects of Hand Preference on Attention

Handedness is associated with cerebral hemispheric differences. Normal patterns of brain asymmetries are needed for the neural processing of attention. In order to identify ADHD (Attention Deficit Hyperactive Disorder) children, the use of checklists allows a greater level of accuracy. Here, we will review our data on this subject. Our first study investigated the psychometric properties of a scale developed to assess attention disorders. Our second study investigated the relationship between handedness and attention disorders using the factors derived from the scale. Our third study included the use of a continuous visual test of attention (CVAT) and examined the relationship between handedness and CVAT variables. For the first and second study, 239 students were included. From this sample, 42 students were selected to participate in the third study. Forty-five teachers rated the children. Four factors were extracted: hyperactivity/impulsivity (explained variance = 36.3%); inattention (11.4%); social isolation (5.2%) and self-confidence (explained variance = 3.3%). Sixty-eight children were included in the ADHD group. We found a higher number of consistent left-handers in the ADHD group as compared to the normal group and a significant effect of handedness on factor hyperactivity/impulsivity. This indicated that left-handers showed greater problems in the hyperactivity-impulsivity domain as compared to right-handers. Considering the data derived from CVAT, a significant handedness effect was found only for the variable commission errors. Left-handers with attention problems showed the greatest number of errors and normal dextrals the lowest number of errors. Normal left-handers made significantly more errors than normal dextrals. Commission error is a parameter that is commonly viewed as a measure of impulsivity. Our data show that hyperactivity/impulsivity is related to handedness, because left-handers present more problems in impulsive behavior than right-handers and suggest that consistent left-handed subjects show greater probability to develop ADHD as compared to right-handed subjects.