Abstract
Although inferences of causality from contingencies are problematic, as Hume argued, and are difficult to prove empirically, explanatory accounts of normal language acquisition and all remedial interventions rely on presumptions of environmental effectiveness. Careful sequential analyses of verbal behaviors can strongly corroborate dependencies by means of establishing either (a) contiguous contingencies or (b) topographical resemblances between antecedents and delayed consequences that could not be explained without assuming such dependencies. The promises, as well as the methodological and conceptual challenges, of such sequential analyses of verbal training and learning are exemplified on the basis of mother-child interactions. Concomitant variation over shorter and longer intervals, and immediate as well as lagged contingencies, are interpreted as indicators of dependency relationships. By focusing on behavioral evidence, extensive similarities or even homologies between first-language training and learning and basic behavioral principles established mostly through nonhuman research can be demonstrated. Nevertheless, expansions and innovations in the behavioral repertoire are suggested as conducive to mutual enrichment of the two fields of the experimental analysis of behavior and first-language acquisition.