Chapter 1. Memory Span

1.1 Introduction

Cognitive Tool Kit
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Memory Span

In this experiment, you will be asked to memorize lists of different types of items and recall them in order. What we are interested in is how the different types of items impact how many items you can correctly recall in a row.

1.2 Experiment Setup

1.3 Instructions

Instructions

You will be presented with a list of items to remember. After the list has been presented, you will see a series of buttons that are matched with the items you have seen; there may also be some items you have not seen. Some items may be repeated in some lists. Your task is to press the buttons in the order in which you originally saw the items. After you have pressed the buttons for the items you recalled in the list, press the Next Trial button to proceed to the next list. The lists will be of different types of stimuli, and the lengths of the lists will vary.

1.4 Experiment

Begin Experiment

1.5 Results

Results

1.6 Debriefing

Debriefing

This experiment examined how much information you can store in your immediate memory, called short-term memory or working memory. The point of this experiment is to find out how much you can remember right now, at this moment.

George Miller (1956), in his now-classic paper, “The magical number seven, plus or minus two,” reviewed a wide range of studies and found that for a number of perceptual and immediate memory tasks, this limit of 7 plus or minus 2 items seems to be pretty close to a universal feature of our cognitive operations. Our data mostly falls within this range. We can see this limit in many of the memory tasks we do on a daily basis. If we ignore area codes, phone numbers are 7 digits long. Zip codes are either 5 or 9 digits long, depending on whether we use the extra 4 digits. Social Security numbers are also 9 digits long. So the numbers people are asked to remember are 5 to 9 items long. These examples are our 7 plus or minus 2 in real-world applications.

But while this limit of short-term memory is important, another feature, also seen in our data, is vitally important as well. We tested several different types of items in the experiment. The item could be a single digit, as in a phone number, or it could be a word made up of many letters. Still, the list seems to mostly fall in the range of 7 plus or minus 2. If we can treat the item as a single unit, it takes only one slot in our short-term memory. Miller (1956) also observed this feature of data; it is this grouping of information into single items that he described as our ability to chunk items in short-term memory. The bigger the chunk, the more information we can retain in our short-term memory. Anything that helps us group information can help us in our chunking. In your studying, you might see how grouping information might help you in your studying.

References:

Baddeley, A. (1994). The magical number seven: still magic after all these years? Psychological Review, 101(2), 353-356.

Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, 81-97.

Wicklegren, W. A. (1964). Size of Rehearsal Group and short-term memory. Journal of Experimental Psychology, 68, 413-419.

1.7 Quiz

Quiz

Question 1.1

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1
Correct.
Incorrect.
The independent variable is the value that is changed by the experimenter. In this experiment, this variable is the type of item in the list, whether numbers, letters that rhyme, and so forth.

Question 1.2

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1
Correct.
Incorrect.
The dependent variable is the value the experimenter collects to indicate how you performed in the experiment. In this case, it is the longest list remembered correctly.

Question 1.3

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1
Correct.
Incorrect.
Chunking is the grouping of information in memory so that it can be treated as a single item in immediate memory. This ability allows us to hold more information in our immediate memory.

Question 1.4

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Correct.
Incorrect.
The finding that the number of letters recalled in the word lists is greater than in the lists of letters alone supports the concept of chunking in our data.

Question 1.5

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Correct.
Incorrect.
It is George Miller who wrote the classic paper The Magic Number 7 plus or minus 2, in which he proposed both this number as the limit for our immediate memory and the concept of chunking.