In this study, we used a novel application of the previous paradigm provided by Pomplun to examine the eye movement strategies of using minimal working memory in visual comparison. This paradigm includes two tasks: one is a free comparison and the other is a single sequential comparison. In the free comparison, participants can freely view two horizontally presented stimuli until they judge whether the two stimuli are the same or not. In the single sequential comparison, participants can only view the left-side stimuli one time, and when their eyes cross the invisible boundary at the center of the screen, the left-side stimuli disappear and the right-side stimuli appear. Participants need to judge whether the right-side stimuli are the same as the disappeared left-side stimuli. Eye movement data showed significant differences between the single sequential comparison and free comparison tasks that suggests the use of minimal working memory in free comparison. Moreover, when the number of items was more than three, an average of 2.87 items would be processed in each view sequence. Participants also used the alternating left-right reference strategy that made the shortest scan path with the use of minimal working memory. The typical eye movement strategy in visual comparison and its theoretical significance were discussed.
Keywords: comparative visual search task; eye tracking; minimal use of working memory; saccade strategy.