Microsaccades distinguish looking from seeing

Abstract

Understanding our visual world requires both looking and seeing. Dissociation of these processes can result in the phenomenon of inattentional blindness or ‘looking without seeing‘. Concomitant errors in applied settings can be serious, and even deadly. Current visual data analysis cannot differentiate between just ‘looking‘ and actual processing of visual information, i.e., ‘seeing‘. Differentiation may be possible through the examination of microsaccades; the involuntary, small-magnitude saccadic eye movements that occur during processed visual fixation. Recent work has suggested that microsaccades are post-attentional biosignals, potentially modulated by task. Specifically, microsaccade rates decrease with increased mental task demand, and increase with growing visual task difficulty. Such findings imply that there are fundamental differences in microsaccadic activity between visual and nonvisual tasks. To evaluate this proposition, we used a high-speed eye tracker to record participants in looking for differences between two images or, doing mental arithmetic, or both tasks in combination. Results showed that microsaccade rate was significantly increased in conditions that require high visual attention, and decreased in conditions that require less visual attention. The results support microsaccadic rate reflecting visual attention, and level of visual information processing. A measure that reflects to what extent and how an operator is processing visual information represents a critical step for the application of sophisticated visual assessment to real world tasks.

The interplay between task difficulty and microsaccade rate: Evidence for the critical role of visual load

“…In comparison to Krueger et al (2019), our mental load condition required some degree of visual information processing and visual load was induced through a task demanding some mental information processing. In Krueger et al (2019) the mental load was induced trough a mental arithmetic task requiring no visual information processing and the visual load was induced through a visual task requiring some mental information processing. Krueger et al (2019) found that the increase in visual load lead to an increase in microsaccade rate.…”

“…In summary, previous research has shown that task load modulates microsaccade rate; visual load is associated with an increase in microsaccade rate while mental load is associated with a decrease in microsaccade rate (c.f. Krueger, et al, 2019). But it is not clear yet whether inducing visual or mental load is decisive for changing microsaccade rates.…”

“…In this context, the considerable interest in research (e.g. Hicheur, Zozor, Campagne, & Chauvin, 2013;Siegenthaler et al 2013;Gao, Yan, & Sun, 2015;Dalmaso, Castelli, Scatturin, & Galfano, 2017;Krueger et al, 2019). However, the result pattern of studies addressing the relation of microsaccade rate and task load is rather diverse and complex.…”

“…Although results of some initial studies comparing different types of cognitive load (e.g. Krueger et al, 2019;Xue et al, 2017) indicate that the visual component of the load is highly important for microsaccade occurrence, there is still some lack of clarity regarding the influence of non-visual task load.…”

“…Research on microsaccades has been very popular in the past decade ( 1 , 2 ), with a considerable deal of effort being put into investigating causes for the modulation of microsaccade rate ( 3 , 4 ). In this context, the influence of task load on microsaccade rate attracted considerable interest in research ( 5 , 6 , 7 , 8 , 9 ). However, the result pattern of studies addressing the relation of microsaccade rate and task load is rather diverse and complex.…”