Looking while loaded: Differences in oculo-motor tendencies during three common visual tasks might be based on varying degrees of cognitive load.

ERWAN David1, PIERRE Lebranchu2, MELISSA L.H. Võ1 
1Scene Grammar Lab, Department of Psychology, Goethe University, Frankfurt, Germany 
2Nantes University & Nantes University Hospital, Nantes, France 

In the study of eye movements, three visual tasks are often used: free-viewing, exploration followed by a question, and visual search. We noticed in previous experiments that fixation and saccade features differed strongly between tasks and part of the reported viewing tendencies could be related to the task rather than the type of stimulus. Surprisingly, few studies have directly compared these tasks within the same experiment, making comparisons difficult due to variations in the type of stimulus material and data processing between studies. Therefore, we set out to explore oculo-motor differences of participants each performing the three different visual tasks, using pictures of indoor and outdoor scenes. We hypothesized that dissimilarities arise because of differences in top-down task requirements rooted in different degrees of cognitive load. To test this, we measured reaction times to an auditory distractor as well as pupil dilations. Our results showed that saccade amplitudes were longest during free-viewing trials. We observed that average saccade amplitudes decreased over time following trial onset during exploration with question and visual search trials, whereas they increased during free-viewing. Additionally, observers needed less time to react to an auditory stimulus when it was presented during free-viewing trials. Further, pupil dilation was on average at its highest during visual search and lowest during free-viewing trials. This study, once again demonstrates the impact of a visual task on oculo-motor tendencies. Importantly, we suggest that the differences that have been reported across tasks might be largely explained by effects of cognitive load.

[This study was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), project number 222641018 SFB/TRR 135 TP C7 granted to MLHV.]

Contact: david@psych.uni-frankfurt.de