Distractor Task Effects on the Serial Position Effect

Introduction

The serial position effect is a well-established phenomenon that reflects human memory processes (reviewed by Murdock, 1962). When a listener is given a word list of about a dozen or more words and is asked to recall them, they will tend to remember the first and last words better than the middle words; thus, the position of the words in the list determines how well the human mind is able to recall them. The terms used to describe the differential ability to remember the first and last words are called the primacy and recency effects, respectively.

A number of different variables can be used to influence the shape of the serial position effect curve. For example, short word lists tend to increase the recall rate for middle words, such that the serial position effect curve as a whole moves upward along the vertical axis (Murdock, 1962). The primacy and recency effects are therefore suppressed as the word list lengthens. Both the primacy and recency effects were also found to be independent of the content of the word lists. Such studies reveal the dynamic nature of the serial position effect under different conditions.

Glanzer and Cunitz (1966) tested whether the interval between presentation of the word list and the recall task had an impact on the serial position curve. They proposed that the primacy and recency effects were the products of long-term and short-term memory processes, respectively, and therefore a delay would affect only the recency effect. Their findings supported this hypothesis by revealing a significant difference in recall rates for the last words on the list when there was a 10 or 30-second delay (p < 0.001).

This project builds upon the work of Glanzer and Cunitz (1966) by assessing the effect of a 30-second distractor task inserted between presentation and recall of the word list. We propose that the distractor task will have no impact on the primacy effect for the first four items in the word list when compared to immediate recall rates. We also propose that the distractor task will have a significant negative impact on the recency effect.

Materials and Methods

To investigate the impact of a distractor task on the recency effect, a convenience sample of 300 undergraduate psychology students enrolled in a cognitive psychology course was utilized. Other demographic information, such as age and gender, was not collected under the assumption that these variables would not have a significant impact on the dependent variable. All subjects enrolled in the study provided informed consent.

A word list of 17 words, matched for frequency and concreteness, was used to test the serial position effect. The distractor task involved counting backward from 300 in threes for 30 seconds.

The word list was presented to study subjects verbally at a rate of one word per second in a monotone voice. The recall task was performed after the complete 17-word list was given to the subjects under two distinct conditions. The first condition required subjects to recall as many words as possible immediately after the word list was finished. The second condition involved engaging in the distractor task immediately after hearing the word list and then attempting to recall as many words as possible. Subjects were not required to recall the words in any specific order and were given an unlimited amount of time to complete the task. The average time for completing the recall task was 2 minutes.