The Serial Position Effect of Free Recall

Recently Murdock (1960) has shown that in free recall RI, the total number of words recalled after one presentation, is a linear function of t, total presentation time. Nothing was said about the serial position effect, though this is a well-known phenomenon of free recall (e.g., Deese & Kaufman, 1957). However, given that there is a serial position effect, the simple linear relationship between Ri and t is rather surprising. In the customary serial position curve of free recall, probability of recall is plotted as a function of serial position. This means, then, that the area under the serial position curve is equal to RI, the number of words recalled after one presentation. If RI is a linear function of t then it must follow that the area under the serial position curve is also a linear function of t. However, it is not immediately apparent how the serial position curve varies with t in such a way as to maintain this simple linear relationship. The present experiment was designed as an attempt to determine how the serial position curve varied with list length and presentation rate while still maintaining this linear relationship. Unfortunately, at the end of the experiment it was still not clear how this relationship came about or, for that matter, whether the relationship was even linear after all. The basic reason for this failure was 1 This study was supported by a research grant, M-3330, from the National Institutes of Health. The author would like to thank Ellen Lissner, Cynthia Marvin, and Frank Warhurst for analyzing the serial position data. that the trends which did show up were not consistent enough to justify any clear-cut conclusions. However, a rather definite picture of the serial position curve itself did emerge from the data. Therefore, the present article will be restricted to a quantitive description and attempted explanation of the serial position curve of free recall.