Auditory predictions are phonological when phonetic information is variable

ABSTRACT

An emerging body of studies has claimed that exposure to phonetically varying speech sounds results in strictly phonological representations of speech sounds by the brain’s auditory prediction system (Cornell et al., 2011; Eulitz & Lahiri, 2004; Hestvik et al., 2020; Hestvik & Durvasula, 2016; Phillips et al., 2000). We test this claim by measuring mismatch negativity (MMN) to a subcategorical contrast with two sets of phonetically varying standards. When controlling for non-prediction related contributors to the MMN, we find a mismatch in a late time window. However, the mismatch effect is only significant for participants who perceived the contrast as an across-category contrast (/t/ vs /d/). Additionally, we find no modulation of mismatch amplitude predicated on phonetic distance between standards and deviant. Taken together, this indicates that the prediction generated by the auditory system in response to phonetically varying speech sounds is indeed phonological and lacks any fine-grained phonetic content.

KEYWORDS:

• Mismatch
• prediction
• phonetic
• phonological

Acknowledgements

The authors would like to acknowledge the work of undergraduate research assistants Lena Herman and Megan Bahnson for their valuable contribution to the execution of this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Six participants had categorization thresholds above 100 ms, but three of these were excluded independently for previously specified EEG data quality issues.

2 “Deviant” here refers simply to the 50 ms VOT stimulus. In the control condition, all stimuli appear with equal frequency, so the 50 ms stimulus is not a true deviant. However, because the 50 ms stimulus will be compared to deviants from the experimental conditions, we refer to it as “control deviant” as a shorthand.

3 For a more conventional deviant-minus-standard analysis, see the Supplemental Material. The effects found in the deviant-standard analysis differs substantially from the deviant-control analysis. In the deviant-standard analysis, we find a significant mismatch effect for both groups of participants in an early (252-352 ms) and late (452-552 ms) time window. In the deviant-control analysis, we find significant results only in the late (452-552 ms time window) and only for the >50 ms group. Although the results of the deviant-control analysis are more limited, we believe they have greater validity because the control paradigm controls for stimulus quality and stimulus frequency.