An analogue assessment of hand stereotypies in two cases of Rett syndrome.

Stereotype hand movements are one behavioural manifestation of Rett syndrome, a neurodegenerative disorder resulting in severe mental retardation. They are neuropathological in origin, and constitute a barrier to the acquisition and exhibition of more developmentally appropriate behaviours, as well as posing a health risk for some individuals. The present study used an analogue assessment procedure, in which experimental conditions were constructed varying in the consequences delivered contingent upon the exhibition behaviour, to examine environmental correlates to the moment-to-moment expression of these behaviours. Results are discussed regarding their implications for intervention and research into the aetiology of stereotypic behaviours.

Operant treatment of orofacial dysfunction in neuromuscular disorders.

The popularity and reported success of biofeedback treatment for neuromuscular disorders has occurred despite a lack of research identifying the critical variables responsible for therapeutic gain. In this study, we assessed the degree to which severe neurological dysfunction could be improved by using one of the components present in all biofeedback treatment, contingency management. Three cases of orofacial dysfunction were treated by reinforcing specific improvements reliably detectable without the use of biofeedback equipment. The results showed that contingency management procedures alone were sufficient to improve overt motor responses but, unlike biofeedback treatment, did not produce decreases in the hypertonic muscle groups associated with the trained motor behavior. The findings suggest that sophisticated, expensive biofeedback equipment may not be necessary in treating some neuromuscular disorders and that important clinical gains may be achieved by redesigning the patient's daily environment to be contingently therapeutic, rather than only accommodating the disabilities of the physically handicapped.

The role of discriminative stimuli in concurrent performances.

Key pecking in pigeons was examined under concurrent and parallel arrangements of two independent and simultaneously available variable-interval schedules. Pecks on the changeover key alternated the schedule of reinforcement for responses on the main key. Under concurrent schedules, discriminative stimuli were paired with the reinforcement schedule arranged in each component and changeover responses also alternated these stimuli. Under parallel schedules, changeover responses alternated the effective reinforcement schedule, but did not change the discriminative stimulus. On concurrent procedures, changeover response rate was inversely related to the difference in reinforcement rate between the two components, whereas on parallel schedules no consistent relationship was found. With both schedules, absolute response and reinforcement rates were positively related, although for a given set of reinforcement frequencies, rates were often higher on the concurrent schedules. On concurrent schedules, relative response rates and relative times were equal to relative reinforcement rates. On parallel schedules these ratios were positively related, but response and time ratios were much smaller than were obtained with comparable concurrent schedules. This inequality was most pronounced when absolute reinforcement frequencies were lowest.