Effects of diet and behavior therapy on social and motor behavior of retarded phenylketonuric adults: An experimental analysis

Abstract

The effects of a low phenylalanine diet on six retarded phenylketonuric adults were assessed. An ABA individual-subject design was used in experiment I to assess the effects of a low phenylalanine diet on social and motor behavior. Following a baseline during which the subjects ingested a normal phenylalanine diet (phase A), a low phenylalanine diet (phase B) was administered in a double blind fashion. Finally, the baseline condition (phase A) was reinstated (normal diet). The low phenylalanine diet resulted in few significant behavioral changes for those subjects with which proper methodologic controls were employed. However, for two of six subjects motor behavior, including stereotypy and tremor, seem to have ameliorated. In experiment II, applied behavior analysis techniques, including differential reinforcement of other behavior and time out, were combined to radically reduce the frequency of stereotypy and self-abuse exhibited by one of the six subjects of experiment I. Speculation: Single-subject methodology borrowed from the experimental analysis of behavior revealed that a low phenylalanine diet was unsuccessful in producing significant desirable behavior changes in four adult retarded phenylketonuric subjects with proper experimental controls. However, when behavior therapy techniques were used with one of these same subjects, a rapid and dramatic reduction in stereotypy and self-abuse was observed. © 1978 International Pediatrics Research Foundation, Inc.