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Re: Increment versus decrement detection

Bruno Repp wrote:
Dear colleagues:

I recently conducted some experiments in which participants had to detect a single changed tone in an isochronous melody consisting of 12 successive complex tones (piano tones) of different pitch but equal loudness. The change to be detected was either in intensity or in duration, and it was either an increment or a decrement. These were four separate tasks, not intermixed. The melody containing the change was immediately preceded by the same melody not containing any change. I would be grateful for comments or references that would help me understand the following trends in my data:

(1) Decrements are harder to detect than increments. Is this well known from previous psychoacoustic research? What is the reason?
Hi Bruno,

You are perhaps familiar with David Huron, "The Ramp Archetype and the Maintenance of Passive Auditory Attention", Music Perception, Vol. 10, No. 1 (1992) pp. 83-92. According to the abstract, "increases of stimulus intensity level are more effective than equivalent decreases in evoking listeners' attention." Huron uses this to explain the fact that it's more usual in music to build slowly & decrease quickly rather than the opposite. I haven't read the paper, but I assume his argument is grounded in evolutionary psychology ideas about the relative advantages of precise detection of increase in things rather than decrease. As one approaches things (or is approached by things) they become larger: something becoming smaller, ie running away, doesn't seem to benefit from a precise perceptual calibration of size difference.

(2) The pattern of variation in detection scores (hits and false alarms) across the 12 tones in the melody, which reflects influences of pitch contour and other factors, is uncorrelated between increment and decrement detection. It seems like these two tasks have little in common. Why?
I'm not sure I understand what you mean by "influences of pitch contour" here. Is there some reason why this experiment requires a melody as opposed to repeating just one note, or making simple variations on two notes, like CCDDCCDD, etc? Also, why did you choose 12 notes?

(3) In increment detection, both hits and false alarms tend to increase across the 12 tones in a melody, but decrement detection shows the opposite trend. It is as if tones were expected to become softer as the melody progresses. Why?

There may be a problem with listener fatigue, something equivalent to the habituation of the orienting reflex. Interest is at its highest at the start, declining as the tune rolls on, if the tune happens to be a not very good one. Assuming that we're more interested in increments than decrements, listeners are overcompensating for even movement at the start, where they more attentive than later. The more interesting thing is increase, because it's more indicative of interesting movement, as per above. So that's what listeners are priming themselves for, and why they would misjudge earlier, or something like that.

I agree with Kevin that it's not possible to say much without knowing what the melodies were.


-- eliot

Many thanks in advance for any helpful replies!