Early work interested in characterizing what may attract attention toward potentially interesting objects in scenes has suggested that changes in illumination on the retina is a particularly effective cue (Franconeri, Hollingworth, & Simons,
2005; Jonides & Yantis,
1988; Yantis & Jonides,
1996). Indeed, abrupt luminance changes are typically observed when a new object appears in the scene; hence, detecting such low-level physical changes using luminance-tuned visual neurons would often quite effectively guide attention toward interesting novel objects (Kahneman, Treisman, & Gibbs,
1992). Other research suggests that sudden changes in color are also effective in attracting attention (Snowden,
2002; Turatto & Galfano,
2001), although this has been more largely debated (Folk & Annett,
1994; Franconeri & Simons,
2003; Jonides & Yantis,
1988; Theeuwes,
1995). Other influences also are tied to the behavioral task which an observer may be engaged in, for example, a search task (Quinlan & Humphreys,
1987; Treisman & Sato,
1990; Wolfe, Cave, & Franzel,
1989). Indeed, the effectiveness of simple bottom-up information, like color and illumination, in attracting attention can be modulated by task influences to yield complex search patterns (Desimone & Duncan,
1995; Evans & Treisman,
2005; Theeuwes,
1994; Treisman & Sato,
1990; Underwood & Foulsham,
2006; Wolfe,
1994). However, the relative strength of contributions from bottom-up information (e.g., salience) versus top-down information (e.g., relevance to a task) in determining what people find interesting remains largely unknown (Henderson,
2003). Possibly, when no specific search target, no search task, and no particular time or other constraint are specified to an observer, bottom-up information might play a predominant role in guiding attention toward potential generically interesting targets (Itti,
2005). Under such conditions (e.g., under free viewing), bottom-up information could provide a strong indication of what people might find interesting in a given scene.