An instance of spurious equivalence relations.

Four normal children learned conditional discriminations that had upper-case or lower-case Greek letters as comparison stimuli, and dictated letter names as samples. Experimental stimuli were three pairs of letters; within each pair, an upper- and a lower-case letter were conditionally related to the same dictated sample. Four control stimuli, also upper- and lower-case letters, were each conditionally related to a different dictated sample. Conditional-discrimination tests for equivalence used the upper- and lower-case letters both as samples and comparisons. Untaught conditional relations between the upper- and lower-case members of each experimental stimulus pair were expected to emerge on the basis of their previously established relations to a common sample. The emergence of conditional relations between control stimuli, however, would have suggested an artifact. In test trials with the experimental stimuli as samples and comparisons, new conditional discriminations emerged as expected with all four children. With two of the children, however, consistent discriminations also emerged between control stimuli. Evidence suggested that uncontrolled features of the program for teaching the children the baseline conditional discriminations might have been responsible for the emergence of untaught conditional relations.