Lab Report - Serial Positioning Effect



Lab Report - Serial Positioning Effect

Introduction

The recency effect refers to the decline in memory performance with the passage of time or the presence of interfering events. Although recency effects in recognition memory are long lived and resistant to interference, recency effects in free and probed recall are short lived and are extremely vulnerable to interference. In this article we analyze the recency effect in free recall, focusing on the details of retrieval under various distractor conditions. In free recall, the recency effect is almost completely eliminated by 15 s of a distractor tasks. The special status of the recency effect in free recall is highlighted by findings that numerous experimental manipulations and participant variables have different effects on recency and prerecency items. For example, list length, interitem similarity, incidental learning and presentation rate significantly affect recall of prerecency but not recency items. In contrast, modality of presentation and interpolated distractor activity affect recall of recency but not prerecency items. (Murdock 1962)

Analyses of the serial position curve in free recall have provided much of the evidence fueling the debate over twostore models of human memory. Using serial-positionbased- analyses, investigators have proposed methods to isolate the contributions of long- and short-term memory to the serial position curve. However, this interpretation of the serial position curve as a straightforward record of the quality of memory is unwarranted. The serial position curve reflects the end product of a rich and dynamic process. Recall probability, a unidimensional measure, fails to capture this process in sufficient detail to constrain theories of free recall. Models of the serial position curve have been based on distinctiveness, spreading activation, forward and backward chaining and, of course, short- and long-term memory. The serial position curve alone has failed to distinguish among these widely varied theoretical approaches. The serial position curve, in collapsing over output positions, discards information about sequential dependencies in retrieval. In this article, we demonstrate that these sequential dependencies can distinguish among competing classes of models. In the experiments reported in this article, two additional measures allow us to examine this process. The probability of first recall measures where in the list participants begin recall. The conditional response probability (CRP) measures how one recall follows another. Taken together, these measures contain more information than the serial position curve that is their result. A theoretical description of each of these measures is necessary for an accurate and complete description of single-trial free recall (Rundus 1971).

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 ...