Negative priming depends on probe-trial conflict: where has all the inhibition gone?

Responses to recently ignored stimuli are often slower than responses to new stimuli. This slowing--referred to as negative priming--has been cited as evidence that selective attention occurs, in part, through inhibition of the processing of irrelevant information, and that selection can occur at postcategorical levels of processing. While negative priming has been observed under a variety of conditions, the slowing can fail to occur if there is no information present that conflicts directly with the correct response. The failure of negative priming to occur under these conditions could provide insight into the specific source of the slowing. In five experiments, the effects of conflicting and non-conflicting information on negative priming were investigated. The results suggest that negative priming will fail to occur under nonconflict conditions only if it is quite apparent that no conflicting information is present. It is suggested that negative priming may be associated with a specific part of the selection process that is involved in protecting the person from making a response based on incorrect information, and that this process only sometimes contributes to reaction time.