Right-, Left-Dominance and Ambidexterity in Grasp Reflex in Human Newborn: Importance of left Brain in Cerebral Lateralization

Abstract

The grasp reflex was studied in human newborn without familial sinistrality. of 60 females, 26 (43.3%) were right-handed and 34 (56.7%) ambidextrous. of 62 males, 20 (32.3%) were right-handed, 39 (62.9%) ambidextrous, and 3 (4.8%) left-handed. There was a nonsignificant preponderance of right-dominance in females and a significant preponderance of nonright-handedness in males. In right-handers, the mean right minus left (R - L) grasp-reflex showed a positive linear correlation with the grasp-reflex from the right and left hands, with a higher correlation for the right hand. In ambidexters, the R - L grasp reflex did not show any significant correlation with the grasp reflex from the right and left hands. The mean grasp-reflex from right and left were found to be significantly smaller in ambidextrous males and females then right-handed males and females, with a much higher significance for the right hand. It was concluded that females tended to have a more pronounced reflex lateralization than males. The results also indicated that the left brain may be more important than the right brain for the development of a spinocerebral motor lateralization in humans.

Key Words:

• Grasp reflex
• cerebral lateralization
• handedness
• newborn
• human