Pupil Dilation as a Substrate for Cognitive Load in Monolingual and Bilingual Infants: A Pupillometry Study on the Bilingual Advantage

The existence of a bilingual advantage in cognitive processing is a popular research topic and is heavily debated. A seminal study by Kovács and Mehler (2009) provided evidence that there is a bilingual advantage in 7-month-old pre-verbal infants in a switching task, although replication findings are inconsistent (Dal Ben et al., 2022; D’Souza et al., 2020; Kalashnikova et al., 2021; Spit et al., 2023). Measuring the pupil dilation response (PDR), a physiological measurement linked to the locus coeruleus (LC) and as such, to cognitive processing load, could give us a more direct look into whether 7-month-old bilingual infants indeed have a cognitive advantage compared to monolinguals. For this pilot study, additional pupil size measurements were taken in the Leiden arm of the replication effort of Spit et al. (2023) to examine whether bilinguals have a smaller PDR from baseline. After hearing a syllable pattern (AAB or ABB) the infants had to predict on which side a visual reward...Show moreThe existence of a bilingual advantage in cognitive processing is a popular research topic and is heavily debated. A seminal study by Kovács and Mehler (2009) provided evidence that there is a bilingual advantage in 7-month-old pre-verbal infants in a switching task, although replication findings are inconsistent (Dal Ben et al., 2022; D’Souza et al., 2020; Kalashnikova et al., 2021; Spit et al., 2023). Measuring the pupil dilation response (PDR), a physiological measurement linked to the locus coeruleus (LC) and as such, to cognitive processing load, could give us a more direct look into whether 7-month-old bilingual infants indeed have a cognitive advantage compared to monolinguals. For this pilot study, additional pupil size measurements were taken in the Leiden arm of the replication effort of Spit et al. (2023) to examine whether bilinguals have a smaller PDR from baseline. After hearing a syllable pattern (AAB or ABB) the infants had to predict on which side a visual reward appeared. The reward side would be the same for the first nine trials in the pre-switch block. The next nine trials had the other syllable pattern and the reward on the other side in the post-switch block. Finally, the last 18 trials mixed both syllable patterns, retaining their associated reward side. The results suggest no difference in cognitive load between the monolingual and bilingual groups when they needed to relearn to predict the target reward side in the post-switch block, nor was there a difference in mean PDR in the association block. This is in line with the results found in Spit et al. (2023) where anticipatory looking behaviour was examined. However, an exploratory analysis suggested there was a significantly larger PDR in monolinguals during stimulus presentation in the pre-switch block compared to the post-switch block, indicating monolinguals had a higher processing load in the first block of the experiment. The implications of this are unclear, but might be explained by an effect related to the unfamiliarity of the task stimuli seen in monolinguals only due to different attentional strategies between the groups. Future research should be done with larger sample sizes and more sophisticated statistical modelling.Show less

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Pupil Dilation as a Substrate for Cognitive Load in Monolingual and Bilingual Infants: A Pupillometry Study on the Bilingual Advantage