Eye Tracking Lexical Processing

Traditional methods of studying language acquisition often rely on behavioral responses that provide a snapshot of the outcome, but not the dynamic unfolding of cognitive processes. In their recent research paper “The development of lexical processing: Real-time phonological competition and semantic activation in school age children,” Jeppsen et al. (2024) sought to understand the real-time mechanisms of word recognition, phonological competition, and semantic activation in school-aged children and adolescents. The researchers recorded participants’ eye movements as they heard words and viewed arrays of images – a version of the Visual World Paradigim (VWP). 

Eye Tracking and Phonological Competition Task

Gaze was recorded with an SR Research EyeLink 1000 eye tracker, which allowed the researchers to precisely track which lexical candidates were activated and how competition among them was resolved over milliseconds.

For instance, in the phonological competition task, participants heard a target word (e.g., “sandal”) while viewing images that included phonologically similar competitors (e.g., “sandwich”) and unrelated items. Eye movements revealed that, at the onset of “sandal” (e.g., “sa-“), participants initially fixated on both the target and the cohort competitor (“sandwich”). As more of the word unfolded, fixations shifted, with the cohort competitor being suppressed and the target becoming the sole focus. This millisecond-level precision, helped reveal the dynamic interplay of activated lexical candidates and the gradual resolution of ambiguity. 

The study found that older children were quicker to initiate target fixations and suppress competitors, indicating more efficient word recognition with age

Eye Tracking and Lexical Processing Task

Jeppsen et al. also attempted to disentangle whether developmental changes in lexical processing were specific to language or attributable to broader domain-general cognitive changes. To address this, they employed a non-linguistic VWP task using colored novel shapes that were not easily namable, providing a purely visual analogue to the spoken word task. 

The researchers extracted similar eye-tracking indices (Target Timing, Competitor Onset, Competitor Offset) from both the linguistic and non-linguistic tasks. By comparing these indices, they could statistically determine the unique contributions of age (indexing language-specific development) versus visual-cognitive skills (indexing domain-general development). The finding that Target Timing in spoken word recognition showed a unique effect of age, even after controlling for visual-cognitive skills, provided compelling evidence for language-specific development. Without the detailed eye-tracking data from both tasks, such a nuanced distinction would have been impossible.

Power of Incorporating Eye Tracking in Psycholinguistics

The Jeppsen et al. (2024) study highlights the power of eye-tracking technology in psycholinguistics. By providing a continuous, high-resolution record of attention and cognitive processing during language comprehension, eye tracking allowed the researchers to:

• Uncover the real-time dynamics of phonological competition and word recognition.
• Distinguish between language-specific and domain-general contributions to lexical development.
• Clarify the relationship between phonological processing and semantic activation.

The study illustrates that for research aiming to capture the fleeting, dynamic nature of human cognition, eye tracking is not merely a tool, but an indispensable lens into the mind.

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