Stimuli with identical contextual functions taught independently become functionally equivalent.

A novel learning process that does not require stimulus associations was explored in humans. The hypothesis was that two contextual stimuli taught in separate settings, with different stimuli, become equivalent if they accomplish identical functions with regard to the relations between the stimuli presented with them. The procedure consisted of : (a) first teaching an AB conditional discrimination (e.g., match A1 to B1 and A2 to B2) and then teaching a second-order XAB conditional discrimination in which X1 indicated performing the same selections as in AB and X2 indicated selecting the alternative comparison (e.g., match A1 to B2 and A2 to B1); (b) repeating the procedure with completely new stimuli, YHJ, in which the functions of the Y stimuli were identical to those of X; and (c) conducting a final probe under extinction to verify the equivalence between the X and the Y stimuli. Three experiments were conducted to explore the process and to rule out the influence of alternative variables. Out of these, 13 of the 14 participants matched the stimuli to the same contextual functions. Thus, the hypothesis was verified. These results demonstrate that humans are able to match stimuli according to their functions in relation to other stimuli. This process may be very much involved in language; for example, understanding that words or clauses that have been learned in separate contexts and with separate stimuli share the same meaning. Understanding this process may help to identify learning or developmental problems, such as those shown by persons with autism, and help to treat them.