Four preschool children who were taught to tact a set of Peabody picture cards were unable to emit those same responses under intraverbal conditions. A transfer of stimulus control procedure was used to bring the responses under intraverbal control. A multiple probe design was used to demonstrate experimental control. The results indicate that the transfer procedure was effective in developing the responses as intraverbals, and in increasing the subjects' scores on the Verbal Fluency subtest of the McCarthy Scales. A second study demonstrated that teaching four additional subjects to tact both the items and the class of which the items were members resulted in the untrained emergence of a few intraverbal responses for two of four subjects. For the other subjects and classes, it was still necessary to teach each of the responses as intraverbals, further demonstrating that tacts and intraverbals are separate verbal operants. The implications of these results for the use of Skinner's (1957) analysis of verbal behavior for studying typical language development are discussed.
