Research has shown that suprasegmental cues in conjunction with visual context can lead to anticipatory (or predictive) eye movements. However, the impact of speech rate on anticipatory eye movements has received little empirical attention. The purpose of the current study was twofold. From a methodological perspective, we tested the impact of speech rate on anticipatory eye movements by systemically varying speech rate (3.5, 4.5, 5.5, and 6.0 syllables per second) in the processing of filler-gap dependencies. From a theoretical perspective, we examined two groups thought to show fewer anticipatory eye movements, and thus likely to be more impacted by speech rate. Experiment 1 compared anticipatory eye movements across the lifespan with younger (18-24 years old) and older adults (40-75 years old). Experiment 2 compared L1 speakers of English and L2 speakers of English with an L1 of German. Results showed that all groups made anticipatory eye movements. However, L2 speakers only made anticipatory eye movements at 3.5 syllables per second, older adults at 3.5 and 4.5 syllables per second, and younger adults at speech rates up to 5.5 syllables per second. At the fastest speech rate, all groups showed a marked decrease in anticipatory eye movements. This work highlights (1) the importance of speech rate on anticipatory eye movements, and (2) group-level performance differences in filler-gap prediction.
Keywords: aging; anticipatory eye movements; bilingualism; speech rate; visual world paradigm; wh-movement.