Consolidation and retention of auditory categories acquired incidentally in performing a visuomotor task

A wealth of evidence indicates the existence of a consolidation phase, triggered by and following a practice session, wherein new memory traces relevant to task performance are transformed and honed to represent new knowledge. But, the role of consolidation is not well-understood in category learning and has not been studied at all under incidental category learning conditions. Here, we examined the acquisition, consolidation and retention phases in a visuomotor task wherein auditory category information was available, but not required, to guide detection of an above-threshold visual target across one of four spatial locations. We compared two training conditions: (1) Constant, whereby repeated instances of one exemplar from an auditory category preceded a visual target, predicting its upcoming location; (2) Variable, whereby five distinct category exemplars predicted the visual target. Visual detection speed and accuracy, as well as the performance cost of randomizing the association of auditory category to visual target location, were assessed during online performance, again after a 24-hour delay to assess the expression of delayed gains, and after 10 days to assess retention. Results revealed delayed gains associated with incidental auditory category learning and retention effects for both training conditions. Offline processes can be triggered even for incidental auditory input and lead to category learning; variability of input can enhance the generation of incidental auditory category learning.