Further work revealed this effect to be a function of the amount of intervening time, not of the number of intervening items. When false alarms are plotted against the amount of time since the item last occurred either as a probe or as a memory set item, an exponential decay function provides a better fit to the data than does a power function. In addition, the serial position data based upon positive probes demonstrates a recency effect but not a primacy effect. We hypothesized that the phenomenon is based upon recognition in the presence of an episodic recollection of the occurrence of a probed item, and that the episodic recollection disappears with time. In the present study, participants indicated the presence or absence of such an episodic recollection.
Results confirm our hypotheses and produce a replication of earlier results.
This effect was manifested in a procedure that involved a Sternberg-like task utilizing memory sets of 18 items followed by 5 recognition probes. In another experiment we demonstrated that the effect and its decay are fundamentally a function of the time since the probed item was last seen and only fortuitously a function of the number of intervening items. Here we have fitted the data with an exponential decay function and a power function. Figure 2 presents these serial position data along with predicted serial position functions constructed by using parameters from the exponential and power fits from Figure 1. These results prompted us to favor the exponential over the power function as a fit for our results.