University of Alberta Dictionary of Cognitive Science: Incidental Learning

The incidental learning paradigm is an experimental paradigm used to investigate learning without intent. Using this paradigm, several groups of subjects are presented with the same list of items (e.g., 20 words) and are instructed to process them in different ways (different orienting conditions), with each group asked to perform a different activity or orienting task with the list. For example,

count the number of letters in each word (shallow processing)
name a rhyming word for each item (again, shallow processing, but deeper than #1
form an image of each word and rate the vividness of each image (deep processing).

Importantly, subjects are not told that there will be a subsequent test of memory. At the end of the list presentation, subjects are unexpectedly asked to recall as many of the words as possible. Processing information at a deeper level results in superior recall of that information (Eysenck, 1974). This suggests that incidental learning can be theoretically linked to the notion of levels of processing (Craik & Lockhart, 1972).

References:

Craik, F. I. M., & Lockhart, R. S. (1972). Levels of processing: A framework for memory research. Journal of verbal learning and verbal behavior, 11, 671-684
Eysenck, M.W. (1974). Age differences in incidental learning. Developmental Psychology, 10, 936-941.

(Revised March 2010)