Salience is in the eye of the beholder: Increased pupil size reflects acoustically salient variables

‘Salience’ is a term frequently used in linguistics but an exact definition for the concept is lacking. Recent technological advances which allow us to explore the cognitive processing of so-called salient linguistic features could provide us with quantifiable measures of ‘salience’, and lead to a further understanding of the concept and its relationship to language acquisition and change. In this paper we measure pupil dilation with the assumption that auditory salience results in a change in pupil size, as an effect of cognitive load. We report an experimental study observing Dutch participants' pupil sizes when listening to stimuli containing salient and non-salient variants of linguistic variables (e.g. Dutch coda/r/; speech intensity, word frequency). Using Generalized Additive Mixed Modelling (GAMM), we find pupil size increases for three of six stimuli categories. We consider our findings in light of the speech processing literature, address the (dis)advantages of the technique, and formulate some recommendations for future advances in neurophysiological measures in (socio)linguistics.