Behavioral competition in a case of Rett syndrome

Major behavioral features of Rett syndrome are the loss of instrumental reaching and grasping and the presentation of some variant of hand-hand or hand-mouth stereotypy. As part of an experimental home intervention program, a 3-year-old girl with Rett syndrome was exposed to four types of contingency games designed to elicit instrumental reaching, kicking, vocalization, and eye movement, respectively. Parent and subject performance were videorecorded on seven occasions over the initial 2-month period. Evaluation of these records provided evidence of contingency learning in all but the vocalization games. Stereotypic hand clasping was examined in relation to the performance of instrumental behavior (reaching, kicking, looking). Coincidental (short-term mutual inhibition arising by chance co-occurrence), associative (short-term mutual inhibition arising by having elicitor in common), and foundational (long-term mutual inhibition arising by having neural network in common) forms of specific behavioral competition were defined and examined. Evidence for coincidental and foundational competition was found in the relation between reaching and hand clasping. Implications for the support of functional hand use are discussed.