To assess 'soft-sign' persistence and its correlates outside a referred sample, 159 members of a local birth cohort of the United National Collaborative Perinatal Project were traced and their performance on six neurological test scales was measured at age 17 by examiners blind to their status at age seven. A comparison group was also formed, who had been 'sign-free' at age seven. On four of the six tests (dysdiadochokinesis, mirror movements, dysgraphesthesia and motor slowness) index boys did significantly worse than the comparison boys; by contrast, index girls scored significantly worse than comparisons only on motor slowness.
Shafer, S. Q., Stokman, C. J., Shaffer, D., Ng, S. K., O'Connor, P. A., & Schonfeld, I. S. (1986). Ten-year consistency in neurological test performance of children without focal neurological deficit. Developmental Medicine and Child Neurology, 28(4), 417-427.