Chapter 1. Memory Span

1.1 Introduction

Cognitive Tool Kit
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Memory Span

Background

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. There seems to be a feature of our immediate memory that limits how long a list we can recall at a time. George Miller (1956), in his now classic paper, reviewed a wide range of studies and found that for a number of perceptual and immediate memory tasks, this limit of 7 +/-2 items seems to be pretty close to a universal feature of our cognitive operations. But while this limitation is important, another feature of our ability to use our immediate information was even more impressive and important. It does not seem to matter what size each item in the list is. The item could be a single digit as in a phone number, or it could be a name made up of many letters. If we can treat the item as a single unit, it takes only one slot in our immediate memory. We will examine both features of our immediate recall in this experiment.

References:

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.

1.2 Experiment Setup

1.3 Instructions

Instructions

You will need to press the space bar to begin the experiment. At the beginning of each trial, a fixation mark will appear. Please look at this mark. 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 and possibly 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 in the list you recalled, 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 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 +/-2, in which he proposed both this number as the limit for our immediate memory and the concept of chunking.