Thirty-six healthy participants received a discrimination learning task requiring the identification of a relevant stimulus dimension. After successful learning, the relevant dimension was shifted unannounced. All exemplars of the two dimensions presented after the shift were novel, implying a "total change" design. In three experimental…

In this article, I discuss the concepts of "private stimuli," "covert responses," and "private events," emphasizing three aspects: the conditions under which private stimuli may acquire discriminative functions to verbal responses, the conditions of unobservability of covert responses, and the complexity of events or phenomena described as…