Treating selective mutism in a paediatric rehabilitation patient by altering environmental reinforcement contingencies.

Selective mutism is a disorder which can cause severe social and academic impairment, and for which a wide variety of treatment approaches have been used, with varying degrees of success. Selective mutism can be conceptualized as the lack of generalization of a class of operant responses (e.g. audible and comprehensible verbalizations) across environmental contexts. The rehabilitation hospital setting, in which the patient is seen daily by multiple people in multiple settings, is particularly well-suited for implementing a systematic behavioural intervention to establish verbal behaviour and simultaneously reinforce its generalization. Data are presented on a 7-year-old female admitted to a rehabilitation hospital following orthopaedic surgery, who met the DSM-IV diagnostic criterion for selective mutism. Additional medical diagnoses included cerebral palsy, microcephaly, and mild mental retardation. A behavioural programme was developed and implemented to reinforce differentially first any communication, then verbal communication across staff and settings. Results were evaluated using a modified multiple baseline across settings design, and demonstrate that verbal, written, and tangible reinforcement effectively increased verbal behaviour where it previously rarely occurred. Results are discussed in terms of the relationship between selective mutism, social phobia and related disorders. The theoretical roles of behavioural phenomena (discriminative stimuli, stimulus generalization) in the development and treatment of these disorders are discussed.