A great deal of prior work has focused on identifying the factors that drive saccadic decisions while inspecting static scenes or performing visual or visuomotor tasks (e.g., Epelboim et al.,
1995; Epelboim & Suppes,
2001; Hayhoe & Ballard,
2005; Johansson, Westling, Bäckström, & Flanagan,
2001; Kibbe & Kowler,
2011; Kowler,
2011; Land & Hayhoe,
2001; Land, Mennie, & Rusted,
1999; Malcolm & Henderson,
2010; Motter & Belky,
1998; Najemnik & Geisler,
2005; Pelz & Canosa,
2001; Steinman, Menezes, & Herst,
2006; Torralba, Oliva, Castelhano, & Henderson,
2006; Turano, Geruschat, & Baker,
2003; Wilder, Kowler, Schnitzer, Gersch, & Dosher,
2009; Yarbus,
1967). Much of the discussion has surrounded the relative role played by
bottom-up versus
top-down factors in controlling saccadic decisions. Bottom-up factors refer to the properties of the visual stimulus itself, typically, the contrast of visual features of the display (Koch & Ullman,
1985). Top-down factors encompass everything else, including voluntary attention, the judged importance or relevance of different locations, the constraints imposed by limitations of memory, and (in the case of visuomotor tasks) the coordination of eye and arm. Tatler, Hayhoe, Land, and Ballard (
2011) concluded on the basis of a recent review that top-down factors are more important than bottom-up factors in driving saccadic decisions but that an understanding of the nature and operation of the relevant top-down factors is a complex endeavor that is still at a relatively early stage.