On each trial, after three squares of different sizes (inducing display) were sequentially presented at central fixation, a target square was briefly lateralized to the right or left hemisphere (RH or LH) of 24 normal right-handed males. Subjects determined whether or not the target differed in size from the third inducing square. Half of the targets that differed were consistent with size changes in the inducing display (e.g., a target smaller than the third square in an inducing display presented in a large-to-small order) and half were inconsistent. Three retention intervals (RIs) between offset of third inducing square and onset of target were used. At the shortest RI, error–rate differences in responding to consistent vs. inconsistent targets, i.e., representational-momentum (RM) effects, were larger in the RH than in the LH, and RM effects in the RH, but not in the LH, were affected by RI.

The development of functional and equivalence classes was studied in four high-functioning, preschool-aged autistic children. Initially, all subjects failed to demonstrate match-to-sample relations indicative of stimulus equivalence among two three-member classes of visual stimuli. Then, 2 subjects showed emergence of those relations after they were taught to assign the same name to all members in each class. Next, subjects were taught names for new stimuli outside the match-to-sample format. On subsequent match-to-sample tests, 2 subjects demonstrated untrained conditional relations among the stimuli given a common name. New, unnamed stimuli were then related via match-to-sample training to stimuli from sets of named stimuli. Tests for emergent conditional relations between the new unnamed stimuli and the named stimuli yielded positive results for 1 subject and somewhat mixed results for 3 subjects. Finally, without naming, 2 subjects developed stimulus equivalence among two new three-member classes of visual stimuli. These data suggest that naming may remediate failures to develop untrained conditional relations, some of which are indicative of stimulus equivalence.