Running Head: THE SERIAL POSITION EFFECT
The Forgotten Middle Child of Memory: The Serial Position Effect
Michelle Lynn Smith
Middle Tennessee State University
The Forgotten Middle Child of Memory: The Serial Position Effect
In our lives, there are many situations in which we are required to remember lists of items. We are presented with situations as simple as remembering what we were supposed to buy at the grocery store to more complicated situations of having to memorize lists of vocabulary words in school in our everyday lives. Thus it is important to know and understand how we remember such things so we can effectively recall them when necessary. Typically, we are not required to remember the exact order or position in which items were presented when recalling them. According to Francis, Neath, MacKewn, & Goldthwaite (2004) this type of recall, in which "the order of the items is not required for accurate recall," is often termed free recall (pg. 60).
However, many researchers have found that the likelihood of recalling items (such as words, letters, or numbers) does in fact depend on the items position in a list. This is often referred to as the serial position effect. The most common finding is that words at the beginning and end of the list are often easier and more accurately recalled than those words in the middle of the list. The improved recall for the words at the beginning of the list is often referred to as the primacy effect. Likewise, the improved recall of the words at the end of the list is referred to as the recency effect. Thus, when the results of a free recall experiment are plotted on a graph a u-shaped serial position curve is often formed.
Many researchers have attempted to explain the serial position effect. A common explanation of the primacy and recency effects were introduced by Atkinson & Shiffrin (1968). According to this viewpoint the primacy effect is a result of the greater amount of attention and rehearsal allocated to the first few items on a list. This advantage in processing given to those items allows them to be transferred into the long-term memory store and thus have a higher probability of being retrieved out of long-term memory. They (Atkinson & Shiffrin, 1968) attributed the recency effect to signify output from what they referred to as primary memory in the form of a short-term memory buffer. Thus, the most recent items viewed in a list are still in short-term memory and are recalled there.
A large amount of research has been done in order to demonstrate this two part memory system as an explanation of the serial position effect. Evidence that the primacy effect is due to a greater amount of rehearsal to the first few items is clear in a study done by Rundus (1971). In this study subjects were asked to rehearse out loud and it was recorded. After reviewing the recordings Rundus (1971) found that participants devoted more overt rehearsal to the first few items on the list. Another example of research supporting the two part memory system explanation shows that the primacy effect should be reduced or eliminated if all of the words on a list are rehearsed an equal number of times. In a study done by Welch & Burnett (1924) participants were asked to only rehearse the items while they were being presented. As a result the primacy effect was either reduced or eliminated among the participants. Thus, by having participants attempt to transfer all of the items into long-term store the primacy effect is reduced. Research done by Glanzer & Cunitz (1966) also showed that primacy is reduced when the items are presented at a faster rate, thus eliminating opportunity for extensive rehearsal by the participants.
Research has also been done to demonstrate the use of short-term memory in explaining the recency effect. Because the recency effect is explained by a retrieval of items from short-term memory, it should be eliminated if a person is asked to do another task before they are asked to recall the items on the list. This was demonstrated in experiments by both Postman & Phillips (1965) and Glanzer & Cunitz (1966). Both studies provided evidence in support of the short-term memory account for the recency effect by having their participants perform a "distractor activity" after the last item on the list but before they were signaled to begin recalling the list items. Postman & Phillips (1965), for example, asked participants to do a small arithmetic task before recalling the list items. Both studies showed a reduced or eliminated recency effect due to "filling" the short-term memory buffer with other tasks, causing participants to have difficulty recalling the last few items on the list. Thus, the last items on the list had "decayed" from short-term memory.
The following experiment investigated the effects of list position on free recall, otherwise known as the serial position effect. In this experiment a free recall of letters was used to demonstrate the effect. A hypothesis in relation to the explanation of the serial position effect that suggests that it is due to the operation of two kinds of memory (long-term and short-term) was tested. The hypothesis was that the letters at the beginning and end of a sequence of letters would be more accurately recalled than those in the middle of the sequence. More specifically the hypothesis that a primacy effect, which in theory is due to improved rehearsal of the items, would be present was tested. A hypothesis that a recency effect, due to the remaining of the last few items in short-term memory, would be present was also tested.
The participants in the experiment consisted of one female Middle Tennessee State University undergraduate enrolled in a Cognitive Psychology course. The student participated as a requirement in the course in order to write a research report on the experiment. The participant did not fail to complete the experiment.
The experiment was conducted through the use of a computer program on Cog Lab on a CD, which was included with the textbook required for the Cognitive Psychology course the participant was enrolled in. The CD program was run on a Dell Desktop computer with a 17Ó monitor. The participant used an attached mouse to respond during the experiment.
The Cog Lab CD that ran the experiment included a book containing explanations, additional references, discussion questions, and written instructions for all of the experiments on the CD. The experiment was under the Memory Processes section of the book/CD and was titled Serial Position.
Once the CD was loaded on the computer, a selection of different types of experiments is displayed on the screen. The Memory Processes Ð Serial Position option was pressed using the mouse. Next a screen was displayed with a blank space on one side and buttons representing each letter of the alphabet on the other side. To begin the experiment, the Next trial button was pressed using the mouse. Then in the blank space on the left side of the screen a sequence of ten letters was presented separately. Each letter was displayed for one second. After all ten letters are presented, the buttons representing each letter of the alphabet on the right side of the screen become clickable. Using the mouse, the participant pressed what they remembered to be the letters presented in that sequence in any order. After ten buttons were pressed, all of the buttons became un-clickable again. Thus, the participant had to select ten letters and no more than that. Each letter could only be selected once for each sequence. After ten buttons had been pressed, the participants then pressed the Next trial button to go to the next sequence of letters. The experiment consisted of fifteen of these types of sequences all containing different letters each time. After completing the experiment, another screen appeared displaying the results for the participant. These results included a data summary of the percent of correctly recalled items at each position in the sequence, a graph plotting those percentages, and a list of the presented and recalled letters for each of the fifteen trials.
The results were analyzed using the Cog Lab CDÕs displayed results for the experiment. A primacy effect was displayed in the 1st serial position in the list percent correct being 86.67%. A strong recency effect was also shown with both the 9th and 10th position in the listÕs percent correct being 93.34%. The strength of the recency effect is also clear when the list of the letters presented and the letters recalled is reviewed (see table 2). All of these positions in the listÕs percent correct were higher than those in the middle positions (see table 1). For example, the 4th, 5th, and 6th serial positions in the listÕs percent correct were only 46.67%, 73.34%, and 60.00%.
The results showed a weak u-shaped serial position curve when graphed (see figure 1). The weakness of the serial position curve is displayed in the 3rd and 8th serial positions in the listÕs percent correct (see table 1). The 3rd serial position in the list's percent correct rose back up to the same percentage as the 1st serial position, which was much higher than the 66.67% of the 2nd serial position. In theory, this percentage should have continued to decrease as it became closer to the middle of the positions in the list. The 8th serial position decreased to 66.67%, when it should have been increasing as it got closer to the end of the positions in the list.
The results did confirm the serial position effect. Although the u-shaped curve wasnÕt as strong as it usually is, the results did show a primacy and recency effect. Thus, our hypotheses were for the most part confirmed. More letters at the beginning and end of a sequence of letters were more accurately recalled than those in the middle of the sequence. A decent primacy effect and a strong recency effect were present in the results as hypothesized.
The traditional u shaped curve consists of a two part memory system according to Atkinson & Shiffrin (1968). The results of this experiment do support this theory in that a primacy and recency effect was indeed present in the free recall task. However more variations of this experiment could better prove the involvement of greater rehearsal of the first few items and their transfer into the long-term memory and the last few items remaining in short-term memory in relation to the serial position effect. Also, a much larger sample size in the future may also provide a stronger and more prominent u shape when the results are graphed. In conclusion, the effect of serial position, primacy and recency, in free recall tasks is unmistakable and has helped to develop the role of two separate systems in memory.
Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. Psychology of learning and motivation: II, 249.
Francis, G., Neath, I., MacKewn, A., & Goldthwaite, D. (2004). CogLab on a CD. Belmont: Wadsworth.
Glanzer, M., & Cunitz, A. R. (1966). Two storage mechanisms in free recall. Journal of Verbal Learning & Verbal Behavior, 5, 351-360.
Postman, L., & Phillips, L. W. (1965). Short term temporal changes in free recall. Quarterly Journal of Experimental Psychology, 17, 132-138.
Reed, S. K. (2004). Long-Term Memory. In Cognition Theory and Application (pp. 97-124). Belmont: Wadsworth.
Rundus, D. (1971). Analysis of rehearsal processes in free recall. Journal of Experimental Psychology, 89, 63-77.
Welch, G. B., & Burnett, C. T. (1924). Is Primacy a Factor in Association-Formation. American Journal of Psychology, 35, 396-401.
Position in List Percent Correct
Trial by Trial Data
Trial Presented Recalled
1 DNASXJFCIT DNASXIJTFC
2 QVJSKHYTFW WQVFJXYKHG
3 OBNIDLARYQ WQVFJXYKHG
4 DKGBMVSWUC WCOGNYSVKU
5 PLFBMEJKQA BLFPJKQANO
6 YBRTVXHKAN ANYBRTJKUM
7 CZMOWEFHJX JXWBCMOKFS
8 RPLHIXVSTN VSTNRBLQJK
9 IRACGFONSJ CGFORNKIAS
10 ZYQSLTVHNK NKZYQRTLVJ
11 XDCLFZGSKE KEXLDFRYQJ
12 KZHFWITVPJ RIVKSWTYJA
13 PFHKCMVEQL QLJKRVCFEH
14 QOUMSTYIZL IZLQFUKTSE
15 JQAIYLMUCW LMUCWJAKYT
Figure 1. Data Summary Line Graph