Abstract
M.A.
The study aims to determine whether statistically significant differences exist
between boys with attention deficit hyperactivity disorder (ADHD) and boys
without ADHD with regard to hemispheric language lateralization and the
laterality of various modalities (handedness, eyedness and footedness).
According to the literature, a possible connection exists between abnormal
lateralization patterns and various developmental disorders (Corballis, 1983;
Geschwind & Behan, 1982; Hiscock, 1988, McFarland, 1981; Turkewitz, 1988).
Lateralization in the current study refers to hemispheric language specialisation,
hand dominance, foot dominance and eye dominance. In most people these
functions are lateralized to the one side of the body by the age of seven (Kalat,
1995; Kolb & Whishaw, 1996). They typically manifest a dominant left
hemisphere for language and a right-sided dominance for handedness,
footedness and eyedness. The result is a dominant left hemisphere, due to the
left side of the brain controlling the right side of the body. Some children
however manifest insufficient or poor lateralization of these functions. For
purposes of this study, it would imply that the functions of language
specialisation, handedness, footedness and eyedness are not all lateralized to
one side of the body. A possible connection between this poor or insufficient
lateralization and ADHD might exist.
According to the DSM IV (1997) the essential feature of ADHD is a persistent
pattern of inattention and/or hyperactivity/impulsivity that is more frequent and
severe than is typically observed in individuals at a comparable level of
development. Some of these symptoms causing impairment must have been
present before age seven, although many individuals are only diagnosed after
the symptoms have been present for a number of years. Impairment resulting
from the symptoms should be present in at least two settings, for example, at
school and at home. Clear evidence must exist of interference with
developmentally appropriate social, academic, or occupational functioning.
An empirical study was conducted in order to compare the hemispheric
language specialisation, handedness, eyedness and footedness of the various
subjects. The subjects consisted of 20 ADHD boys (8 -12 years) who met the
criteria of the DSM IV and 20 Non-ADHD boys (8-12 years) without any learning
problems. Various interference variables were controlled in the selection of the
subjects (see section 5.2.3)
Kimura's dichotic listening technique was used to measure hemispheric
language specialisation and the Harris-test for Lateral Dominance was used to
measure handedness, eyedness and footedness.
Wilks's lambda, Pearson's chi-quadrant and Student's t-tests were used during
statistical analysis of data.
Results indicated statistically significant differences between ADHD boys and
non-ADHD boys with regard to hemispheric language specialisation,
handedness and footedness. Overall, the results indicated that the ADHD boys
are not as strongly lateralized as the non-ADHD boys. The non-ADHD boys
showed a stronger left hemispheric language specialisation, right hand
dominance and right foot dominance. No statistical differences were recorded
with regard to eyedness.
The current study provides possible theoretical support for the theory that a
connection exists between poor or insufficient lateralization patterns and children
with ADHD. However, the study only focused on white boys between the ages of
8-12 years. Further studies involving different age groups, cultures and gender
are recommended.