Emergence of New Stimulus Classes by Exclusion in Children and Adolescents

Abstract

Children and adolescents from four age groups (4, 8, 11, and 14 years of age) learned the baseline conditional relations for the emergence of two three-member equivalence classes. Then, they were exposed to exclusion trials that included baseline stimuli as defined stimuli to be rejected, while another, undefined stimulus had to be selected in the presence of an undefined sample. Emergent performance in symmetry and transitivity relations with stimuli related by exclusion was tested to probe for evidence of the emergence of a new stimulus class (class 3). Then, participants were exposed to new exclusion trials which employed class 3 stimuli as defined stimulus, and symmetry and transitivity conditional relations were again tested with the new stimuli related by exclusion to identify the emergence of a new class (class 4). Participants of the four age groups showed emergence and expansion of equivalence classes by exclusion, and use of the exclusion class stimuli as a basis for the emergence of a new class by exclusion. The likelihood of equivalence emergence with stimuli related by exclusion decreased in 5-year-old children when symmetry and transitivity were tested for exclusion classes, but did not for baseline classes. Some sources of control for accurate responding to the tests are discussed.