Chapter 27 - Saccadic search: On the duration of a fixation

Abstract

This chapter answers the question that is it the fixated stimulus element or the fixation history that determines fixation duration. It measured 93,922 fixations to investigate how fixation times are adjusted to the demands of a visual search task. Subjects had to search for an O between C's. The C's could have a large gap or a small gap. The proportions of both types of C's in the displays were varied. The main results are that: fixation time depended on the element fixated, fixation time on large gap C's decreased with increasing proportion of large gap C's in the display, and fixation time on large gap C's depended on the gap size of the previously fixated element. The chapter concludes that fixation time depends both on the fixation history and on the current fixation element. The contribution of both components on fixation time may depend on the task and the amount of useful information in the displays. Pre-programming of fixation times appears to be conservative such that extension of fixation time occurs in the next fixation whereas shortening of fixation time appears to be delayed.