Operant conditioning of vocalization rate of infants with Down syndrome.

Reinforcement control over vocalization rates of infants with Down syndrome was evaluated; elicitation of vocalizations by social stimulation was controlled. Parents of three infants (2.7, 5, and 8.2 months old) provided social reinforcement under two schedules: continuous reinforcement for vocalization (CRF) and differential reinforcement of other-than-vocalization (DRO). All infants produced systematically higher vocalization rates during CRF, even though the amount of social stimulation during DRO was equal to or greater than the amount provided during CRF. The results replicated findings with normally developing infants and support a contingent-stimulation model of intervention for infant vocal communication.