The relationships between the degree of grasp-reflex asymmetry, grasp-reflex strength from the right and left hands, and body weight in the male and female newborn with and without familial sinistrality.

The relation of the degree of grasp-reflex asymmetry to the strength of right- and left-hand grasp-reflex strength and body weight was studied in human newborn. In the total sample (N = 103), the right minus left (R-L) reflex strength was found to be positively linearly related to the grasp-reflex strengths from the right and left hands in FS-subjects; the correlation was higher for the right hand than the left hand. In FS+ subjects (N = 17), there was not a significant correlation between R-L and right-reflex strength; left-reflex strength was found to be negatively linearly related to the R-L reflex strength. In FS- subjects, the right- and left-reflex strengths showed a positive linear correlation with body weight. In FS+ subjects, only the left-reflex showed a positive linear correlation with body weight. The R-L reflex tended to be positively correlated with body weight in FS- subjects and negatively correlated in FS+ subjects. In females (N = 58), the relation of R-L to right and left reflex was similar to that for the total sample. There was no significant correlation between grasp reflex and body weight in FS- females. In FS+ females (N = 8), there was a positive linear correlation between the right grasp-reflex and body weight; the left grasp-reflex did not show such a significant correlation. The R-L grasp-reflex strength was not correlated with body weight in females.(ABSTRACT TRUNCATED AT 250 WORDS)