Retrospective revaluation in humans: Learning or memory?

The phenomenon of retrospective revaluation has posed considerable problems for many associative learning theories as it involves a change in the asso ciative strength of a cue on trials on which that cue is absent. The presen t series of experiments pursues this idea of changes in associative strengt h between evoked representations of cues, in an effort to establish, de nov o, an excitatory connection between two cues simultaneously activated in me mory. Given the finding of Dwyer, Mackintosh, and Boakes (1998) that simult aneous activation of absent cues in the memory of rats resulted in learning comparable to that seen in retrospective revaluation, we expected that if retrospective revaluation was found in humans, then excitatory learning due to simultaneous activation would also be seen. This was not the case. The implications of our results are discussed in terms of Dickinson and Burke's (1996) modified SOP model and a version of McLaren's (1993) APECS network. We conclude that many of the effects attributed to learning in retrospecti ve revaluation studies are better thought of as due to changes in the retri evability of items in memory.