Processing of Different Molecular Representations in Stereochemistry Tasks: Insights from Eye-Tracking

This study investigates how experienced chemists interpret two common molecular representations, ball-and-stick (BAS) and wedge-and-dash (WAD), by examining their eye-movement patterns during a molecule-comparison task. Ten doctoral students and postdoctoral researchers completed six tasks in which they decided whether or not two molecules were identical while their gaze behavior was recorded with a screen-based eye tracker. Fixations were analyzed using molecule-level areas of interest, and fixation/transition ratios (FTRs) were used to characterize focused versus comparative behavior. Participants also reported their strategy use and perceived difficulty. Across the sample, WAD tasks elicited significantly longer total fixation durations and higher FTR values than BAS tasks, indicating greater overall cognitive load and more sustained focus within individual molecules. Average fixation duration did not differ between representation types. Half of the participants employed an analytical strategy based on determining the molecules’ absolute configuration (R/S), and these individuals tended to show more focused behavior and often rated WAD representations as easier to interpret. Participants relying on mental rotation instead began with more comparative viewing and shifted toward focused behavior as they approached a decision. Strategy use appeared to drive many of the observed gaze-pattern differences. The study highlights substantial differences between molecular representations but also underscores the importance of teaching analytical strategies in chemistry education to reduce the cognitive demand of abstract representations.