Miller’s law, chunking, and the capacity of working
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Miller’s law, chunking, and the capacity of working
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[post_date] => 2024-12-25 13:42:28
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[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
In 1956, George Miller asserted that the span of immediate memory and absolute judgment were both limited to around 7 pieces of information. The main unit of information is the bit, the amount of data necessary to make a choice between two equally likely alternatives. Likewise, 4 bits of information is a decision between 16 binary alternatives (4 successive binary decisions). The point where confusion creates an incorrect judgment is the channel capacity. In other words, the quantity of bits which can be transmitted reliably through a channel, within a certain amount of time.
Chunking, or clustering, is the function of grouping information together related by perceptual features. This is a form of semantic relation, such as types of fruit, parts of speech, or 1980s fashion. Chunking allows the brain to increase the channel capacity of the short term memory; however, each chunk must be meaningful to the individual. There are many other memory consolidation techniques. The peg memory system creates a mental peg from an association, such as a rhyme, letter, or shape. Another memory technique is the link system, where images are creating links, stories, or associations between elements in a list to be memorized.
A researcher wanted to challenge the limits imposed by Miller’s Law (7 plus/minus 2). In the study ( n = 20, H0 = 7 plus/minus 2), subjects completed a backward digit span test and other memory tests administered during each of five sessions over the course of a year. The backward digit span test consisted of five trials during each session. Each trial began with instructions and a statement of understanding from the subject. Each backward digit span test began with two digits and was read at a rate of one digit per second. The digit span length increased until there were three incorrect attempts. The digits must be repeated in reverse order by the subject (researcher – “3,5,6,2,3,1” subject – “1,3,2,6,5,3”). The results for the average longest correctly repeated string of digits over all sessions by each subject are shown in Table 1 below.
Table 1: The averaged results of the backward digit span test throughout all 25 trials (5 trials, 5 sessions) for each subject (n = 20). Mean (μ) = 4.73, Confidence interval at 95% [4.02, 5.45], Standard deviation (σ) = 1.48, p-value , and the significance criterion (α) was 5%.
Adapted from: Miller, G. A. (1956). The magical number seven, plus or minus two: some limits on our capacity for processing information. Psychological review, 63(2), 81.
[post_title] => Miller’s law, chunking, and the capacity of working
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[question] => Which system of the working memory model was the researcher testing by utilizing the backwards digit span test?
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[answer] => 3
[description] => Reason for the Correct Answer:
The Central Executive supervises the cognitive process of memory.
The Articulatory Rehearsal Component had minimal effect on the test since there was not enough time for rehearsal before the subject was required to repeat the digit string.
The Phonological Store is being tested. It is believed that the phonological store capacity is around 2 seconds.
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[each_answer] => A. Central Executive
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[each_answer] => B. Episodic Buffer
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[each_answer] => C. Phonological Store
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[each_answer] => D. Articulatory Rehearsal Component
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => Which of these mistakes could have caused a Type I error in the study shown in Table 1?
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[answer] => 1
[description] => Reason for the Correct Answer:
A Type I error, or a false positive, is the incorrect rejection of the null hypothesis. A Type II error, or a false negative, is the incorrect acceptance of a null hypothesis that is actually false.
In this study, the null hypothesis (stylized as H0) is that the average number of correct digits repeated back by the subject is 7 plus/minus 2. This statement can be written as H0] = 7 plus/minus 2.
The results of the study found that the average number of correct digits repeated back was 4.73 with a significance of p-value 2.32 x 10⁻⁵. As this was below the significance criteria of 5%, the null hypothesis is rejected. If this rejection of the null hypothesis is correct, the studies findings represent a true positive. However, there is a possibility that the null hypothesis was incorrectly rejected, which would represent a false positive or Type I error.
The speed that the subject repeats the digits back to the researcher would not affect the number of digits they remembered, and thus could not have caused a Type I error.
Reading the digits to the subject too slowly would cause an increase in performance, as it would be easier for the subject to remember the digits. The study already found a significant decrease in performance, which would mean that the true performance would be even worse than the study found. In this case the null hypothesis was still correctly rejected (although the magnitude of the change was incorrect), meaning it could not be a cause of a Type I error.
Reading the digits to the subject too quickly would cause performance on the test to decrease because of the difficulty in remembering the quickly read digits. This decrease in performance is potentially consistent with the decrease in performance found in the study. Thus reading the digits to the subject too quickly would be a potential cause of a Type I error.
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[each_answer] => A. The researcher read the digits too quickly.
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[each_answer] => B. The researcher read the digits too slowly.
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[each_answer] => C. The subject repeats the digits too quickly.
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[each_answer] => D. The subject repeats the digits back too slowly.
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => What can be inferred about the researcher’s study (Table 1) assuming that none of the respondents had been diagnosed with an attention or memory disorder?
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[description] => Reason for the Correct Answer:
The confidence interval is the chance that the mean falls between the given lower and upper bound.
The average is the middle value in a set of data; a p-value that is less than the significance criterion denotes that the results were significant.
The results were extremely significant; the average digit span recalled was 4.73 digits across all subjects.
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[each_answer] => A. The results were extremely significant; the average digit span recalled was 4.73 digits across all subjects.
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[each_answer] => B. The chance of a Type II error, or a false negative, is 5%.
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[each_answer] => C. There is a 95% chance that the results are significant; the average subject recalled an average of 4.73 digits.
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[each_answer] => D. 95% of the variance of the sample can be explained by the speed at which the terms were read by the participants in the backwards digit span test.
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[quiz_unique_key] => 2261298308
[question] => How many successive binary decisions are represented by 64 binary alternatives?
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[answer] => 2
[description] => Reason for the Correct Answer:
2 successive binary decisions would equal 4 binary alternatives.
32 successive binary decisions would equal 4,294,967,296 binary alternatives.
6 successive binary decisions would equal 64 binary alternatives, 2⁶ = 64.
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[each_answer] => A. 2 successive binary decisions
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[each_answer] => B. 6 successive binary decisions
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[each_answer] => C. 32 successive binary decisions
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[each_answer] => D. 128 successive binary decisions
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[quiz_unique_key] => 574431310
[question] => Which of the following scenarios is utilizing a chunking technique?
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[answer] => 1
[description] => Reason for the Correct Answer:
The peg memory system utilizes numbers, rhymes, shapes, and sounds to create a scene based on a mental ‘hook’, but is not a chunking technique.
The link system utilizes order and connections (links) to facilitate memory recovery, but is not a chunking technique.
Acronyms such as PAD are an example of mnemonics.
Writing down information helps to reinforce the memory, but it is not a chunking technique. However writing information down by category, such as in the example of the grocery list, is an example of chunking.
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[0] => Array
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[each_answer] => A. Writing down a grocery list by category.
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[each_answer] => B. The word being memorized is connected to other words in a list; the order facilitates recovery of the list items.
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[each_answer] => C. Using an acronym, such as “PAD” to represent peripheral artery disease.
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[each_answer] => D. Creating a scene where each member of a list is represented by a number, rhyme, shape, or sound.
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