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A four-member equivalence class (A----B----C----D) can be formed by training AB, BC, and CD. The nodal stimuli, B and C, mediate all of the derivative (transitive and equivalence) relations in the class. The derivative relations AC, CA, BD, and DB are separated by one node, whereas AD and DA are separated by two nodes. How do the number of nodes that separate the stimuli in a derivative relation influence the induction of stimulus control exerted by that relation? Seven college students learned two four-member classes made up of nonsense syllables. After training, all derivative relations were presented repeatedly without informative feedback. Stimulus control exerted by each derivative relation was assessed concurrently. For the 7 subjects, control exerted by the derivative relations increased gradually with repeated presentations. With 6 of the 7 subjects, the one-node relations exerted more control than the two-node relations during the process. However, the disparity between the one- and two-node relations decreased with repeated presentations. Eventually, all derivative relations exerted complete control. The control exerted by derivative relations during induction was inversely related to the number of nodes separating the terms in the derivative relations. These results demonstrate that nodal distance is a determinant of the relatedness of stimuli in equivalence classes. The findings are discussed in terms of remote association, semantic memory networks, and the study of transitive inference.

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The 32 studies that met these criteria relied on one or more of three conceptualizations of the role of housing: housing attributes or assessments as an outcome or dependent variable; housing attributes as inputs or independent variables in a model in which the outcome pertains to a nonhousing factor, such as a mental health outcome; or housing as both an input and an outcome. Three studies found no long-term effect of improved housing adequacy on housing satisfaction above and beyond case management. Three studies found better outcomes for settings that have fewer occupants. Another study suggested that persons who live in small-scale, good-quality, noninstitutional environments are less likely to engage in disruptive behavior when a larger proportion of other tenants also have serious mental illness. The strongest finding from the literature on housing as an input and an outcome was that living in independent housing was associated with greater satisfaction with housing and neighborhood. Most of the studies had methodological weaknesses, and few addressed key hypotheses. There is a critical need for a coherent agenda built around key hypotheses and for a uniform set of measures of housing an input and an outcome.

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