REPLICATION OF ASYMMETRY OF A-B RIDGE COUNT AND BEHAVIORAL DISCORDANCE IN MONOZYGOTIC TWINS

We have replicated an earlier study (Rose et al., Behav. Genet. 17, 12 5-140, 1987) relating dermatoglyphic asymmetry to intrapair discordanc e in a completely new sample of monozygotic (MZ) twins. Consistent res ults were observed for at least 31 of 37 Minnesota Multiphasic Persona lity Inventory (MMPI) scales tested in the two samples. Intrapair diff erences were confirmed to be greater in 28 MZ pairs with asymmetric pa lmar a-b ridge counts than in 29 MZ pairs with little or no a-b asymme try for at least 15 scales. We also examined longitudinal stability ov er a 4 to 5-year period for six MMPI scales and found suggestive evide nce in three scales for greater test-retest instability in twin pairs asymmetric for a-b ridge count. The results offer new evidence for our hypothesis that an asymmetric a-b ridge count may identify individual s who are poorly buffered from developmental noise, but analyses of sy mmetric and asymmetric a-b ridge counts in nontwin subjects are requir ed to extend and test the hypothesis further.