<qa>  What is the IQ below 40 measured by the Leiter?- IQ below 40 as measured by the Leiter or below a mental age of 18 months on the Receptive Language Scale of Mullen. N.B. subjects who test below 18 months of age, but are otherwise eligible, may be enrolled following a case review by the Steering Committee - e.g., childs uncooperative behavior resulted in a likely underestimate of intellectual ability; 