After backward pairings with a paraorbital shock, a tone CS was an effective punisher of lick ing in rabbits, yet yielded retarded forward acquisition of the rabbit's nictitating membrane response. The observation of both excitatory and inhibitory associative effects after a common training protocol challenges the assumption of a unidimensional associative continuum and sup ports approaches that assert a multidimensional structure to associations. A continuing paradox for associative theories is the mul tiplicity of effects that result from following an aversive US with a CS. When the backward pairings are indirectly assessed with transfer-of-control paradigms, the CS usually suppresses an instrumental baseline (Burkhardt, 1980; Heth, 1976; Mowrer & Aiken, 1954; Williams, Dyck, & Tait, in press). This observation has led to the conclusion that backward conditioning produces excita tory associative effects. In contrast, when the effects of the backward pairings are assessed with a retardation-of learning test, in which the CS and US are paired in a for ward order and the development of CRs to the CS is moni tored, the rate of CR acquisition is usually retarded (Plot kin & Oakley, 1975; Siegel & Domjan, 1971). The re tarded acquisition has led to the conclusion that backward conditioning produces inhibitory associative effects (Hall, 1984). In attempts to resolve the paradoxical effects of back ward pairings, an association has usually been viewed as a unidimensional construct for which excitation and inhi bition are mutually exclusive outcomes. As an associa tion develops with backward pairings, a transient excita tory associative phase is thought to precede a terminal inhibitory association (Pavlov, 1932; Wagner & Terry, 1975). Consequently, research strategies have emphasized functional relationships between associative strength and dynamic variables such as time, number of conditioning trials, and US-CS interval. Accordingly, one assessment procedure is selected, and variables that might affect as sociative strength are manipulated (Heth, 1976; Maier, Rapaport, & Wheatley, 1976; Quesnel, Ten Have, & Tait, 1980; Siegel & Domjan, 1974). This strategy has produced reliable differences in the associative strength accrued to the backward CS, but not reliable evidence for
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