Saturday, January 12, 2008

Biology and phonetic variation

A regular reader of this blog* passed along a reference to a new paper in the journal Medical Engineering and Physics called "Adaptation of wavelet transform analysis to the investigation of biological variations in speech signals", by Julia Rees and a string of co-authors. Here’s the abstract:
The purpose of this study was to adapt wavelet analysis as a tool for discriminating speech samples taken from healthy subjects across two biological states. Speech pressure waveforms were drawn from a study on effects of hormone fluctuations across the menstrual cycle on language functions. Speech samples from the vowel portion of the syllable 'pa', taken at the low- and high-hormone phases of the menstrual cycle, were extracted for analysis. Initial analysis applied Fourier transforms to examine the fundamental and formant frequencies. Wavelet analysis was used to investigate spectral differences at a more microbehavioural level. The key finding showed that wavelet coefficients for the fundamental frequency of speech samples taken from the high-hormone phase had larger amplitudes than those from the low-hormone phase. This study provided evidence for differences in speech across the menstrual cycle that affected the vowel portion of syllables. This evidence complements existing data on the temporal features of speech that characterise the consonant portion of syllables. Wavelet analysis provides a new tool for examination of behavioural differences in speech linked to hormonal variation.
The subject line on the message alerting me to this paper was "Major uber WTF?", but it turns out there really is a lit on the effects of hormones on verbal and motor skills — more estrogen correlates with “improved performance on … verbal tasks”.** The person who sent this along asked these questions:
Are … people going to have to incorporate endocrinology into linguistics now? Can you imagine what the press could do with this?
Yeah, we can all have nightmares about what the media would do with this for sure. I happened to be talking to a biologist and asked him about it. He gave a simple, plausible sketch of things, basically this: Our bodies are complex and interconnected enough that we shouldn't be terribly surprised at finding seemingly bizarre but statistically significant correlations of all sorts. In that light, the notion that hormones could impact motor control, and thus speech, seems pretty straightforward.

Still, it's not clear that it changes anything directly for most of us in linguistics: The differences reported look tiny (if I'm understanding the paper): Anything that has impact on motor control will affect speech. Even much coarser issues of motor control and speech, like intoxication, aren't yet all that well understood, despite tons of good work on the topic, some by Wisconsin's own Tom Purnell and Ryan Hanke.

Image from here.
* I’m far from over the shock that such people exist.
** Yes, the missus has come to grips with these research findings.

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