Phonological discrimination and contrast detection in pupillometry

Julia S C Chiossi; François Patou; Elaine Hoi Ning Ng; Kathleen F Faulkner; Björn Lyxell

doi:10.3389/fpsyg.2023.1232262

Phonological discrimination and contrast detection in pupillometry

Front Psychol. 2023 Nov 1:14:1232262. doi: 10.3389/fpsyg.2023.1232262. eCollection 2023.

Authors

Julia S C Chiossi^{1

2}, François Patou³, Elaine Hoi Ning Ng^{1

4}, Kathleen F Faulkner¹, Björn Lyxell²

Affiliations

¹ Oticon A/S, Smørum, Denmark.
² Department of Special Needs Education, University of Oslo, Oslo, Norway.
³ Oticon Medical, Smørum, Denmark.
⁴ Department of Behavioural Sciences and Learning, Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Linköping, Sweden.

Abstract

Introduction: The perception of phonemes is guided by both low-level acoustic cues and high-level linguistic context. However, differentiating between these two types of processing can be challenging. In this study, we explore the utility of pupillometry as a tool to investigate both low- and high-level processing of phonological stimuli, with a particular focus on its ability to capture novelty detection and cognitive processing during speech perception.

Methods: Pupillometric traces were recorded from a sample of 22 Danish-speaking adults, with self-reported normal hearing, while performing two phonological-contrast perception tasks: a nonword discrimination task, which included minimal-pair combinations specific to the Danish language, and a nonword detection task involving the detection of phonologically modified words within sentences. The study explored the perception of contrasts in both unprocessed speech and degraded speech input, processed with a vocoder.

Results: No difference in peak pupil dilation was observed when the contrast occurred between two isolated nonwords in the nonword discrimination task. For unprocessed speech, higher peak pupil dilations were measured when phonologically modified words were detected within a sentence compared to sentences without the nonwords. For vocoded speech, higher peak pupil dilation was observed for sentence stimuli, but not for the isolated nonwords, although performance decreased similarly for both tasks.

Conclusion: Our findings demonstrate the complexity of pupil dynamics in the presence of acoustic and phonological manipulation. Pupil responses seemed to reflect higher-level cognitive and lexical processing related to phonological perception rather than low-level perception of acoustic cues. However, the incorporation of multiple talkers in the stimuli, coupled with the relatively low task complexity, may have affected the pupil dilation.

Keywords: acoustic cues; linguistic context; novelty detection; phoneme perception; pupillometry; speech perception.

Grants and funding

The project from which this study originated has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement n. 860755.