Refining behavioral phenotypes: personality-motivation in Williams and Prader-Willi syndromes.

Despite behavioral differences, individuals with Williams or Prader-Willi syndrome share a proneness to certain personality characteristics. We hypothesized that there are qualitative differences in these shared personality features. Personality-motivation (measured using the Reiss Profiles) was compared for equal numbers of age- and gender-matched individuals with Williams or Prader-Willi syndrome or mental retardation due to nonspecific causes. Each syndrome featured aberrant motivational profiles, and similarities were found across groups in various domains. Significant differences emerged in the specific stimuli that motivated behavior in several Reiss Profile domains. Implications are discussed for the "classic" sociable personality in Williams syndrome and for compulsivity in Prader-Willi syndrome. Recommendations are made for treatment and more refined phenotypic research.