How fixation durations are affected by search difficulty manipulations

ABSTRACT

Many eye tracking studies of visual search have focused on the role of the number of fixations and the nature of scan paths. Less attention has been paid to fixation durations and to how those durations are affected by stimulus features. Previous studies have shown that fixation durations can be as important as the number of fixations in explaining search times with complex stimuli (e.g., in search for specific faces). In the present study, simple stimuli were used in a search experiment where participants searched for a closed ring among rings with a gap. We manipulated distractor heterogeneity (DH), target-distractor similarity (TDS), and stimulus density (SDY, set size within a constant search window), and estimated the contributions of these factors to gaze behaviour and trial search time. The results show that fixation durations contribute less to variation in overall search time with simple search stimuli as compared to previous studies with more complex stimuli. However, fixation durations still increased with DH, TDS, and SDY. These effects were mainly additive, and we did not find an interaction between DH and closer element spacing at high levels of SDY that might have been expected since both DH and SDY influence distractor grouping.

KEYWORDS:

• Visual search
• fixation duration
• distractor heterogeneity
• target-distractor similarity
• element spacing

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by the German Research Foundation (DFG) grant ER 962/1-1 to Daniel Ernst.