Murdock free recall data: The initial recall search identifies the context by the location of the least remembered item and produces only better remembered items in proportion to the total recall difference.

Abstract

The curious free recall data of Murdock (1962) shows an additional surprise that seems to have gone undetected until now: the probability of guessing an item in the initial recall is not identical to the overall free recall curve. Initial recall of an item is well correlated with the total recall of that item using a straight line but with an unexpected offset. The offset varies with the presentation rate and the total number of list items but in each case it is the same as the total recall probability of the least recalled item. Thus for the initial “freest” of recalls the location of the least remembered item is identified, in effect identifying the context, and from there the items recalled are those better remembered items, in proportion to the probability of total recall. Within the tagging/retagging model (Tarnow, 2008, 2009) the free recall starts by an identification of a discontinuity in the activity level and produces an item with a probability according to the relative activity level. I speculate that the activation level and its discontinuity is detected by glial cells assisting in rebuilding post-activation empty presynaptic neurotransmitter vesicles.