Linguistic diversity begins with our palates

The different accents of the world may have their origins in the shapes of our mouths, according to new research. An international linguistic team has found that variations in the layout of the hard palate – the bony roof of the mouth – influence how people from different ethnic backgrounds pronounce vowel sounds.

But these influences are initially very small. What then happens is that subtle variations in vowel sounds are amplified across generations as children mimic their parents, and in time marked accents emerge.

Dan Dediu and colleagues from the Max Planck Institute for Psycholinguistics in the Netherlands wanted to find out what role the anatomy of vocal tracts has played in the growth of linguistic diversity.

Until now, most research has focused on cultural and environmental influences on the evolution of language. Anatomical difference has been assumed to have had little impact.

So the researchers created a computer program that models the human vocal tract, with several “articulators” – such as the tip of the tongue and lips – that can be moved to produce actual speech sounds.

They then fed into this model data from the MRI scans of the hard palates of 107 people from four broad ethnolinguistic groups: European and North American of European descent, North Indian, South Indian, and Chinese.

Finally, they asked the computer model to say five vowels common in many languages: the “uh” in “sofa, the “ee” in ‘meet’, the “a” in bat, the “oo” in “boot” and the “o” in “hot”.

The team found that different hard palate shapes in all groups resulted in small but distinct differences in the acoustics and articulation of all five vowels.

However, the computer modelling also showed that these individual-level speech idiosyncrasies are amplified when passed down through generations, rapidly at first and then more slowly as time passes and pronunciation becomes settled.

This amplification, the researchers say, is a “robust phenomenon”, and in the computer modelling produced vowel patterns similar to those found in real-world dialects and languages.

Writing in the journal Nature Human Behaviour, the authors say their work shows that culture and biology co-evolve.

“Language – similarly to other aspects of culture – is an evolutionary system in its own right, constantly shaped by adaptive pressures.

“It has been suggested that aspects of the physical environment… affect the physiology of speech production differently in different populations, resulting in differences between the speech sounds that occur in different languages.

“However, our own cognitive, physiological and anatomical biases are probably the most important components shaping languages.”

The team acknowledges that their computer modelling is just a start, with several limitations, and conclude that further research is needed to fully understand the role that vocal tract anatomy plays in the evolution of language.

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