Two tests of manual performance were adapted for French children: a do
t-filling test and a tapping test. Sibling resemblance was assessed in
a sample of 46 pairs of sibs. The power of intra-class correlation wa
s estimated by a procedure of Approximate Randomization Tests. In both
tests sibling resemblance was significant for overall level of motor
skill (i.e. when the two hands were considered separately). Sibling re
semblance was significant for degree of laterality in the dot-filling
test (the closest task to writing) but not in the tapping test. The us
efulness of including degree of laterality measures, in future genetic
research is discussed.