On the nature of interactions between the past and the present.

We conceptualize the past and the present as dimensions of experience and ask whether past processing must affect decisions about the present and whether present processing must affect decisions about the past. The paradigm is speeded classification: Ss classified a stimulus's past spatial position and tried to ignore information about present position (Experiments 1-4), or classified present position, while attempting to ignore past position (Experiments 5-6). We found that in classifying the past, Ss were unable to ignore present position, unless it was processed apart from the retrieval cue. In classifying the present, subjects could ignore past position completely. We conclude that a processing asymmetry exists, reflecting perhaps a logical asymmetry in the information required to make past or present decisions.