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At age 17 two motor signs, mirror movements and dysdiadochokinesis, were found in more than half the subjects known to have had the respective signs at age 7. These rates were significantly higher than rates found within the group of subjects who were sign free at age 7.
Shaffer, D., Stokman, C., O'Connor, P.A., Shafer, S., Barmack, J.E., Hess, S.,Spalten, D., & Schonfeld, I.S. (1986). Early soft signs and later psychopathology. In L. Erlenmeyer-Kimling (Ed.). Life-span research on the prediction of psychopathology (pp. 31-48). Hillsdale, NJ: Erlbaum.