SOME DEVELOPMENTAL ASPECTS OF LATERALIZATION AND COGNITION
ROSSLAND, JOHN CLIFFORD
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This study was designed to test whether cerebral lateralization develops and whether lateralization is related to cognitive development, using Piaget's number conservation and class inclusion constructs. It also explored a new method of tactually measuring number conservation.;Three groups of male right-handed subjects with mean ages of 5 years, 7 months; 7 years, 4 months; and 8 years, 6 months were used.;Two measures of lateralization were used. One measure required the subjects to tap on the spacebar of a typewriter with the left and the right hands alternately while silent or speaking. The results indicated that only right hand tapping was significantly slowed down by simultaneous speech. It was suggested that speech interferred with right hand tapping because both the right hand and speech are controlled by the left hemisphere. This task also showed some slight but conflicting evidence of developmental shifts.;The other measure of lateralization was based on Lechelt and Tanne's (1976) study which suggested that the rapid tactual presentation of seven or less pulses would be perceived more accurately with the right hand (and, hence, the left hemisphere, using an analytic counting analysis) and that eight or more pulses would be perceived more accurately with the left hand (and, hence, the right hemsiphere, using a gestalt-holistic analysis that high numbers of pulses would seem to require). In the present study which used children instead of adults this task did not show the expected lateralization effect.;The tactile test of number conservation involved the presentation of pulse trains which contained the same numbers of pulses but with different temporal spacing between the pulses. Subjects were asked if the trains contained the same number of pulses. A correlation emerged between this task and number conservation suggesting that the alteration of the temporal spacing between pulses confused non-conservers as the alteration of space does in the standard number conservation task.;This study did not find any significant relationship between cognitive development and the degree of lateralization as evidenced by performance on the tapping task. There was some slight but conflicting evidence that lateralization develops.