Cognitive Daily

i-eca0cf2af9fc3ac4445c7dff7d8aab70-research.gifOne of the unanswered questions in Krista Hyde and Isabelle Peretz’s research on amusia (“tone-deafness”) is why amusics frequently say they are unable to clap to the rhythm of a song, or to dance well. In Hyde and Peretz’s study, amusics could detect rhythm changes as well as normal individuals, even while being unable to detect changes in musical pitch.

Hyde and Peretz speculated that amusics might not be able to detect rhythm changes when the pitch of the notes change — that their problems with rhythm might be directly related to the fact that amusics can’t detect many changes in pitch. But there is another possibility. Perhaps Hyde and Peretz’s rhythm test was too simple: it involved playing five identical notes at a constant rate, then changing the timing of one note in the sequence. So it’s also possible that amusics have difficulty only with more complex rhythmic structures.

A team led by Jessica Foxton has developed an elegant way to test these two hypotheses. They created four types of rhythmic sequences, each just five notes long. The first, most basic sequence was just five identical notes, played at a constant rate. The second sequence made the rhythm slightly more complex by alternating between tones repeated rapidly and slowly. The final two sequences had the same rhythm as the first two, but instead of playing the same tone, each note was randomly varied.

Volunteers listened to the sequences in pairs, and their task was to determine if the rhythmic pattern of the second sequence was the same as the first. Here’s an example of the complex rhythm:

Sample 1:

Most listeners should be able to detect that the rhythm of the second sequence is different from the first. Foxton’s team systematically varied how different the two rhythms were (the difference was always in the fourth tone), testing both amusics and people with normal pitch peception. They repeated the task with a new sequence that randomly varied the tones played. The rhythm was the same, as were the differences between the second sequence and the first. Here’s an example of this type of sequence:

Sample 2:

Listen for a difference in rhythm between the first set of five tones and the second set — ignore differences in pitch. Could you discern a difference?

The Foxton team’s task was a little more complicated than this, because they adapted the sequences they played based on the accuracy of responses, honing in on the exact threshold where each individual could detect differences between each type of sequence. Here are their results:

i-2ec5e2a88fbfa3a335092e51f42a6961-foxton1.gif

Foxton et al. did indeed find a difference in rhythm perception between people with amusia and those with normal pitch perception. While there was no difference between the variable-pitch and the constant-pitch conditions for normal individuals, for amusics, performance was significantly impaired when they listened to rhythm changes while pitch varied. Interestingly, these pitch changes were large enough that they were probably detectable even by amusics.

So while people with tone-deafness can hear both large pitch changes and small rhythm changes in isolation, when small rhythm changes are combined with large pitch changes, the ability to keep rhythm deteriorates dramatically.

Which means that people with tone deafness should probably not only skip out on American Idol auditions — they should probably stay away from So You Think You Can Dance, too.

And what about the samples I provided? I’ll put an update with the correct response to the poll question in the comments later today.

Foxton, J.M., Nandy, R.K., & Griffiths, T.D. (2006). Rhythm deficits in ‘tone deafness.’ Brain and Cognition, 62, 24-29.

Comments

  1. #1 Oran Kelley
    December 1, 2006

    This is interesting.

    I think that since music and dancing are so very social (we learn to appreciate particular kinds of music and how to respond to it — dancing, say) that experiements with real music might be revealing.

    In Western music, for instance, there’s often a close tie-in between chord changes and rhythmic cycles, so an inability to hear how a chord progession is cueing an upcoming rhtmic change may lead amusic folks to feel they can’t dance well.

    Another thing I wonder about is a phenomenon I heard about–a person who claimed all his life to be tone deaf but who actually wasn’t: he could easily perceive tonal differances. He just hated music. Where other people might get a pleasant senstaion from hearing harmony, it would grate on him terribly. So he avoided music in social situations by claiming to be tone deaf and running off to do something else.

  2. #2 Dave Munger
    December 1, 2006

    Oran,

    You’re right — many people claiming to be “tone deaf” actually aren’t. What Peretz and others have found is that there’s a subset of those claiming tone deafness who do have a real perceptual deficit.

  3. #3 Nicole Brockmann
    December 4, 2006

    I have to note that this is true of trained musicians as well. If I give a rhythmic dictation in which I constantly vary the pitches used, even if the rhythmic pattern is always the same, students do much worse than if I repeat the same rhythmic and melodic pattern over and over again.

    As a nitpicker, I also have to point out that the words “fast” and “slow” are misused above. A longer note is not any slower than a shorter note. “Fast” and “slow” are determined by tempo (the speed of the underlying pulse or beat), not by duration. A 10-hour car ride at 65 mph is not any “slower” than a 1-hour car ride at 65 mph. One lasts longer than the other, but the speed is the same in both cases. I’d also take exception to “played at a constant rhythm.” What I think is meant is “five notes of equal duration.”

    These inaccuracies in terminology seem awfully important if the discussion is about how people perceive the proportionate division of time.

    NB

  4. #4 Dave Munger
    December 4, 2006

    Nicole –

    It would be interesting to test your observation. Since untrained people perceive the rhythm changes equally well whether or not the pitches vary, I’d be fascinated to learn if trained musicians actually perform worse when the pitch of the notes changes. I know that Greta, who has played the oboe since she was in middle school, had some difficulty with the changing-pitch task, while I found both tasks equally easy.

    re: nitpicking — I think I’ve changed the language to be clearer now. I’m always happy to be corrected. (Actually, the duration of the notes was constant, it was the interval between the notes that changed)

  5. #5 Nicole Brockmann
    December 6, 2006

    You can guinea-pig my class anytime! We will be doing a lot of dictation next semester.

    As part of an introductory class on Dalcroze Eurhythmics I have been teaching this semester, I have given rhythmic dictations in exactly this way — varying the pitches every time. The students get dictations in their other classes in which the pitches remain the same; in these cases, they are supposed to write down both pitches and rhythm. Since (as far as I know) we perceive all qualities of sound simultaneously — pitch, duration (though the complete perception of that takes a bit longer, obviously), timbre, loudness/softness, students are not used to isolating these concepts from one another. That is a difficult skill for them. For this particular class, I created a rhythmic pattern and then improvised pitches for it at the piano, every time a different set of pitches (though I did keep them tonally related so as not to go too wacko on them). I then asked students to clap back the rhythm or to walk it, and then to make up their own melodies to the rhythm and to sing them all together, listening only for rhythmic accuracy. While I think that most of what they do as professional musicians requires them to perceive pitch and rhythm simultaneously, I think there is also value in figuring out how to separate and perceive various musical qualities individually.

    Feel free to get in touch if you’d like to work out a little experiment. You can reach me at nicolebrockmann at depauw dot edu.