Joint control and the selection of stimuli from their description.

This research examined the role the two constituents of joint control, the tact and the echoic, play in producing accurate selections of novel stimuli in response to their spoken descriptions. Experiment 1 examined the role of tacts. In response to unfamiliar spoken descriptions, children learned to select from among six successively presented comparisons which varied in their color, shape, and border features. Repeated testing and training revealed that accurate selecting with new combinations of the same colors, shapes and borders, did not occur until after the children could themselves tact the individual color, shape and border features with the unfamiliar descriptions. Experiment 2 examined the role of self-echoics. Here, the stimulus features were given their familiar names, but the rehearsal of these names, while searching among the six successively presented comparisons, was impeded by a distracter task. Under these conditions selection of the correct comparison was found to depend on its position in the order of presentation. Correct comparisons presented earlier in the order, and presumably less effected by the distracter task, were more likely to be selected than correct comparisons presented later in the serial order. Taken together, these data suggest that generalized stimulus selection must be under joint tact/echoic control. The data also illustrate the distinction between mediated selection of a stimulus in response to its description (i.e., selection under joint control) and the traditional conception of an unmediated selection response evoked as a result of a heightened response probability in a conditional discrimination.