A Study on the Effect of Free-Viewing Eye Movement on Microsaccades

Recently, several attempts have been made to quantitatively evaluate covert attention, using microsaccades. Simultaneously, the number of reports on microsaccade-detection algorithms has also increased. In particular, the EK method proposed by Engbert et al. in 2003 and the OM method proposed by Otero–Millan et al. in 2014 are still being utilized in many works. However, most of the microsaccade-detection algorithms proposed so far assume that the measured eye movement data do not include blinks or saccades, and there are very few reports on the detection of microsaccades using measurement data obtained during free viewing, which include such information. If microsaccades can be detected from the measurement data obtained during free viewing, in which blinks and saccades are mixed, it will be possible to evaluate potential attention without requiring fixation in experimental protocols. This can further the applied research on microsaccades. Therefore, in this study, we investigate an algorithm for detecting microsaccades in the measurement data obtained during free viewing, and conduct experiments on the effect of free-viewing eye movements on microsaccades. The results suggest that a combination of a microsaccade-detection algorithm using the EK method and an amplitude threshold may be able to detect microsaccades in free-viewing data as well as fixed-point viewing data.