Relation between Exclusion and Stimulus Equivalence Class Formation in Auditory-Visual and Visual-Visual Matching in Preschoolers

The hypothesis that exclusion performance is a prerequisite for the stimulus equivalence class formation was assessed in preschoolers of about 5 years of age. In Experiment 1, two groups of children were trained in a set of conditional discriminations in a two-choice matching to sample format, Group 1 in an auditory-visual modality baseline, and Group 2 in a visual-visual modality baseline. Exclusion test trials included an undefined (not previously related) comparison stimulus, and a defined (i.e., related in the baseline) comparison stimulus, in the presence of an undefined sample stimulus. Selection of the undefined comparison was recorded as a correct response. Stimulus equivalence class formation was assessed by way of symmetry and transitivity test trials. Experiment 2 replicated the design of the first experiment, with the difference that exclusion was assessed independently and with a different baseline from symmetry and transitivity. Exclusion scores were higher for the auditory-visual groups than the visual-visual groups. In both modalities symmetry scores were superior to those in transitivity. Symmetry showed independent from the exclusion performance, but transitivity was presumably dependent from it in the auditory-visual modality.

Naming New Stimuli After Selection by Exclusion

Responding by exclusion in matching-to-sample tasks is a robust behavioral pattern in humans. A single selection, however, does not ensure learning of the arbitrary relationship between the sample and the selected comparison stimulus. The present study aimed to investigate the amount of exposure required until eight preschoolers were able to name two undefined pictures, matched by exclusion, to two undefined words. After establishing a matching-to-sample baseline between pictures and dictated words, two new words were introduced in exclusion probes. On each probe, a new word was dictated and the matrix of comparison stimuli included a new picture and two experimentally defined pictures. Naming emerged after three to10 exclusion trials. Correct naming tended to occur more reliably when the teaching phase established stimulus control by selection.