In everyday visual search, we are presented with a feature-rich environment that can help guide the search process. For example, Peterson et al. (Psychological Science, 2001) found near-perfect memory when searching a display of 12 items. In contrast, when searching an impoverished environment in which only two possible saccade targets were visible at any one time, memory capacity is reduced to the last 4 items and items at lags 5 and greater are often reexamined as if they had not been previously viewed and rejected (McCarley et al., Psychological Science, in press). A feature-rich environment not only allows for potentially greater spatial localization of examined items through the use of salient landmarks, but also provides knowledge-in-the-world of examined items and future saccade targets. To examine if environmental features can be used to guide search, we used a modified version of the McCarley et al. saccade-target experiment in which several uniquely-colored large static landmarks were added to the display. This allowed us to examine the role that landmarks might play in guiding search when scan path planning and object persistence are unable to guide search. Landmarks appeared in colors different from the search stimuli and were an order of magnitude larger. Surprisingly, the presence of these non-potential targets led to smaller memory spans than when they were absent. This suggests that accidental environmental cues, rather than enhancing memory, instead compete for the memory representation of examined items. In addition, the role of object-persistence and knowledge-in-the-world for examined and to-be-examined items will be discussed.
ASJC Scopus subject areas
- Sensory Systems