Speech behaviour is known to be relatively consistent in individuals. This has been shown, for example, across non-contemporaneous recordings in forensic research (e.g. Rose 2002). Still, gradual shifts may occur in production, especially where sound changes are concerned. This has been shown most famously in the analysis of the Queen's annual Christmas broadcasts (Harrington, Palethorpe & Watson 2000). Changes like this are thought to occur because of constantly evolving speaker/listener experiences. Harrington & Schiel (2017:416) explain that "[i]ncremental sound change due to mutual imitation … is predicted by exemplar models of speech”.

Such a theory also predicts changes in listeners’ behaviour in the sense that remembered exemplars should be gradually evolving as they interact with different speakers. However, it remains an open question over what time scales changes in perception might occur, and longitudinal processing studies on “typical” populations are rare. In the only such study we know of which tracked individuals, Evans & Iverson (2007) showed incremental accent changes in highly mobile young people in the U.K in a two-year period, but changes in their perceptual behaviour were not observed in this time frame.

We analyse longitudinal listening behaviour in a small town in Australia where listeners are not mobile, but where merger of /el/->/ael/ is in progress. The same ten mainstream Australian English listeners took part in a forced-choice vowel categorisation task that was administered in three 3-year increments (2012, 2015, 2018). Despite predictions that incremental changes would be evident amongst listeners, responses were remarkably similar at each time point – even in the context of a merger in-progress. We nevertheless focus on the behaviour of a small number of individuals, who had some variability in their processing behaviour, and consider the reasons for this. We also address theoretical considerations about production-perception misalignment given our findings.

References

Evans, B.G. & Iverson, P. (2007). Plasticity in vowel perception and production: a study of accent change in young adults. Journal of the Acoustical Society of America. Vol. 121 (6), 3814-3826.

Harrington, J. & Schiel, F. (2017). /u/-fronting and agent-based modeling: The relationship between the origin and spread of sound change. Language Vol. 93 (2), 414-445.

Harrington, J., Palethorpe, S. & Watson, C. (2000). Monophthongal vowel changes in Received Pronunciation: An acoustic analysis of the Queen’s Christmas Broadcasts. Journal of the International Phonetic Association Vol. 30 (1/2). 63-78

Rose. P. 2002. Forensic Speaker Identification. London ; New York: Taylor & Francis.