Three imitative responses (head nodding, mouthing, and strange verbalizations) were established in young children by social reinforcement from a puppet. A fourth imitative response (bar-pressing), which was never reinforced, was found to increase in strength when reinforcement followed the other three imitative responses. This increase in imitative bar-pressing was taken to indicate that a generalized similarity of responding between puppet and child could be a reinforcing stimulus dimension in the child's behavior. Two additional procedures were applied to demonstrate further the dependence of imitative bar-pressing upon the reinforcement following the other imitative responses. These additional procedures were extinction of the other imitative responding, and time-out from the other imitative responding. In extinction, reinforcement was no longer presented following imitative head nodding, mouthing, and strange verbalizations, but was instead presented in a noncontingent manner during the normal conversation between puppet and child. As a consequence, imitative bar-pressing decreased in strength. When reinforcement was reinstated for the other imitative responses, imitative bar-pressing again rose in strength. During time-out periods, the puppet ceased to provide the child with head nodding, mouthing, and strange verbalization performances for the child to imitate. Again, social reinforcement was continued at the same rate but was delivered during the normal puppet-child conversation. The effect of the time-out was to decrease the strength of imitative bar-pressing. Reinstatement of the cues and reinforcement for imitative head nodding, mouthing, and strange verbalizations produced increased imitative bar-pressing.
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