Abstract

The study of bidirectional conditioning began more than a century ago, yet it has failed to take strong root in psychology and neuroscience. We revisit this topic by exploiting E. A. Asratyan's alternating procedure of stimulus presentation, in which both forward (e.g., A -> B) and backward (e.g., B -> A) training trials are concurrently given, in order to analyze their potential interaction. Specifically, using a two-alternative, forced-choice task, we trained humans and pigeons to learn associations between stimuli depending on whether they were presented as sample stimuli or choice stimuli. Trials were selected from an associative network in which forward and backward associations between sample and choice stimuli were synergistic (bidirectional network) or from an associative network in which these associations were not synergistic (unidirectional network). Humans were faster to learn associations from the bidirectional network than from the unidirectional network; additionally, they performed poorly on unidirectional trials that allowed for the expression of (incorrect) bidirectional associations. Unlike humans, pigeons showed no evidence of bidirectional associations. The reasons for this species difference as well as future directions for research deploying Asratyan's two-way training technique are discussed.