Pitch Memory Instructor's Page

Pitch Memory Experiment

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Introduction
Task and Stimuli
Requirements
Data Analysis
References

Introduction

When words are presented serially, we can retain a memory of them by rehearsing them. But pitch information is not quite so easy to retain or reinstate as verbal information, perhaps because most people lack not only the ability to attach names to tones but even to reproduce tones faithfully. But still, one would suspect that tones differing in pitch could be reliably judged as different when they are different and as the same when they are the same. This kind of judgment does not require absolute memory of pitch, just relative memory. The task used here, however, shows that even this task can be difficult for many people, particularly for those with no training in music.
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Task and Stimuli

The pitch memory task is patterned after Deutsch (1979). On each trial, a target tone and a test tone are presented with five distracter tones between them. The research participant’s job is to judge whether the target and test tones are the same or different. Performance is measured as percent correct.

The tones used in this experiment were created as pure tones ranging from 220 Hz to 880 Hz. There are 25 tones in all, equally spaced across the interval. The target tone for each trial is selected randomly from the 12 even-numbered tones in the 25-tone series. Test tone selection is constrained to be either the same as the target tone or different by two semitones. Thus the same 12-tone set is used when choosing a target tone but the choice is not random. Distracter tones are selected from the 13 odd-numbered tones in the 25-tone series. Selection is random with the constraint that no tone can repeat as a distracter on any one trial. Thus five unique distracters are presented between the target and test tones. In order to distinguish target and test tones, there is a ½ sec delay between the test tone and the start of the 5-tone distracter sequence. The test tone appears ½ sec after the end of the 5-tone distracter sequence. When target and test tones are different, they can form an ascending or descending series with equal probability.
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Requirements

Because the stimuli in this experiment are auditory, the computer used to present the experiment must have a sound card. Speakers are not necessary because a standard headset can be plugged directly into the sound card. We use this arrangement for computers in public places where speakers are not allowed.
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Data Analysis

An interesting analysis to perform initially compares the observed percent correct for each participant to the chance percent of 50% to determine whether there is evidence that the individual has pitch memory. The appropriate test is a one-tail z-test that uses the statistic

The denominator is the SD of the distribution for percent correct based on N choices each of which has a probability of .5 of being correct (which is the correct probability for people who are in fact guessing). If one wants the same analysis performed on the mean percent correct for the class, the statistic is the same except that the first term in the denominator(the part under the radical) needs to be divided by the number of participants before the square root is taken. This statistic may not be of any interest, however, in that it will be readily apparent that the class on average performed well above chance.

In addition to analyzing percent correct for individuals and for the class, it is also of interest to examine the incorrect trial data. When participants were wrong, did they tend to be wrong by choosing "Same" when the tones were different or by choosing "Different" when they were the same? A chi-square analysis can compare these two proportions. Typically one finds an affirmative bias in same-different judgment tasks. This may reflect a characteristic of human decision making or it may reflect something about participants’ discriminatory ability. The former explanation can be described as a tendency to say "same" whenever one is in doubt. The latter explanation is that different sounds tend to sound the same to those with less discriminating ears.

There are two between subject variables of interest. The first is differences in musical training. When data sets are small, a dichotomous comparison between those with no training and those with training could be used to determine whether those with musical training perform better than those without. An independent samples t-test could be used to judge the significance of the difference. In larger samples, an attempt could be made to determine the functional relation between numbers of years of training and pitch memory. The first step toward this analysis would be a graph of the relation between years of training and mean percent correct. Statistical analyses would employ trend analysis based either on an analysis of variance or a linear or curvilinear regression..

A second between subject variable of interest is handedness Deutsch (1979, 1980) reported that left handers are superior to right handers on pitch memory tasks of the type used here. Deutsch actually recommends a more discriminating measure of handedness than the one we use, which is merely to ask participants whether they have a right, left, or mixed preference. Still, in reasonably large data sets a handedness effect should emerge.
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References

Deutsch, D. (1979). Pitch memory: An advantage for the left-handed. Science, 199, 599-600.

Deutsch, D. (1980). Handedness and memory for tonal pitch. In J. Herron (Ed), Neuropsychology of left-handedness, (pp. 263-271). New York: Academic Press.
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Last revised:January 22, 2010 09:04:06 AM
Copyright© 2010 The University of Mississippi. All rights reserved.
Questions about this page?PsychExps



Pitch Memory Experiment

Back to Instructor's Page
Introduction Task and Stimuli Requirements Data Analysis References
Introduction
When words are presented serially, we can retain a memory of them by rehearsing them. But pitch information is not quite so easy to retain or reinstate as verbal information, perhaps because most people lack not only the ability to attach names to tones but even to reproduce tones faithfully. But still, one would suspect that tones differing in pitch could be reliably judged as different when they are different and as the same when they are the same. This kind of judgment does not require absolute memory of pitch, just relative memory. The task used here, however, shows that even this task can be difficult for many people, particularly for those with no training in music. « Return to Top»
Task and Stimuli
The pitch memory task is patterned after Deutsch (1979). On each trial, a target tone and a test tone are presented with five distracter tones between them. The research participant’s job is to judge whether the target and test tones are the same or different. Performance is measured as percent correct. The tones used in this experiment were created as pure tones ranging from 220 Hz to 880 Hz. There are 25 tones in all, equally spaced across the interval. The target tone for each trial is selected randomly from the 12 even-numbered tones in the 25-tone series. Test tone selection is constrained to be either the same as the target tone or different by two semitones. Thus the same 12-tone set is used when choosing a target tone but the choice is not random. Distracter tones are selected from the 13 odd-numbered tones in the 25-tone series. Selection is random with the constraint that no tone can repeat as a distracter on any one trial. Thus five unique distracters are presented between the target and test tones. In order to distinguish target and test tones, there is a ½ sec delay between the test tone and the start of the 5-tone distracter sequence. The test tone appears ½ sec after the end of the 5-tone distracter sequence. When target and test tones are different, they can form an ascending or descending series with equal probability. « Return to Top»
Requirements
Because the stimuli in this experiment are auditory, the computer used to present the experiment must have a sound card. Speakers are not necessary because a standard headset can be plugged directly into the sound card. We use this arrangement for computers in public places where speakers are not allowed. « Return to Top»
Data Analysis
An interesting analysis to perform initially compares the observed percent correct for each participant to the chance percent of 50% to determine whether there is evidence that the individual has pitch memory. The appropriate test is a one-tail z-test that uses the statistic The denominator is the SD of the distribution for percent correct based on N choices each of which has a probability of .5 of being correct (which is the correct probability for people who are in fact guessing). If one wants the same analysis performed on the mean percent correct for the class, the statistic is the same except that the first term in the denominator(the part under the radical) needs to be divided by the number of participants before the square root is taken. This statistic may not be of any interest, however, in that it will be readily apparent that the class on average performed well above chance. In addition to analyzing percent correct for individuals and for the class, it is also of interest to examine the incorrect trial data. When participants were wrong, did they tend to be wrong by choosing "Same" when the tones were different or by choosing "Different" when they were the same? A chi-square analysis can compare these two proportions. Typically one finds an affirmative bias in same-different judgment tasks. This may reflect a characteristic of human decision making or it may reflect something about participants’ discriminatory ability. The former explanation can be described as a tendency to say "same" whenever one is in doubt. The latter explanation is that different sounds tend to sound the same to those with less discriminating ears. There are two between subject variables of interest. The first is differences in musical training. When data sets are small, a dichotomous comparison between those with no training and those with training could be used to determine whether those with musical training perform better than those without. An independent samples t-test could be used to judge the significance of the difference. In larger samples, an attempt could be made to determine the functional relation between numbers of years of training and pitch memory. The first step toward this analysis would be a graph of the relation between years of training and mean percent correct. Statistical analyses would employ trend analysis based either on an analysis of variance or a linear or curvilinear regression.. A second between subject variable of interest is handedness Deutsch (1979, 1980) reported that left handers are superior to right handers on pitch memory tasks of the type used here. Deutsch actually recommends a more discriminating measure of handedness than the one we use, which is merely to ask participants whether they have a right, left, or mixed preference. Still, in reasonably large data sets a handedness effect should emerge. « Return to Top»
References
Deutsch, D. (1979). Pitch memory: An advantage for the left-handed. Science, 199, 599-600. Deutsch, D. (1980). Handedness and memory for tonal pitch. In J. Herron (Ed), Neuropsychology of left-handedness, (pp. 263-271). New York: Academic Press. « Return to Top»

Last revised:January 22, 2010 09:04:06 AM Copyright© 2010 The University of Mississippi. All rights reserved. Questions about this page?PsychExps