“…autosomal, recessive disorder resulting from the inability of the liver to metabolize the essential amino acid, phenylalanine. Recent investigations have suggested that experiential factors (Friedman, Sibinga, Steisel, & Sinnamon, 1968;) may be implicated in the occurrence of reported behavioral abnormalities (Bjornson, 1964;Jervis, 1954;Koch, Fishier, Shild, & Ragsdale, 1964;Yaker & Goldberg, 1963). Characterization of the behavior of children with PKU by use of a structured interaction procedure indicated that children with this disorder were more variable in their interactional behavior than groups of normal children, retarded children with brain damage, and psychotic children.…”