When do I Quit? The Search Termination Problem in Visual Search
In visual search tasks, observers look for targets in displays or scenes containing distracting, non-target items. Most of the research on this topic has concerned the finding of those targets. Search termination is a less thoroughly studied topic. When i
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Abstract In visual search tasks, observers look for targets in displays or scenes containing distracting, non-target items. Most of the research on this topic has concerned the finding of those targets. Search termination is a less thoroughly studied topic. When is it time to abandon the current search? The answer is fairly straight forward when the one and only target has been found (There are my keys.). The problem is more vexed if nothing has been found (When is it time to stop looking for a weapon at the airport checkpoint?) or when the number of targets is unknown (Have we found all the tumors?). This chapter reviews the development of ideas about quitting time in visual search and offers an outline of our current theory. Keywords Visual attention · Visual search · Target prevalence · Radiology · Airport security · Guided search · Search termination · Absent trials Visual searches, great and small, are a continuous part of our lives. As this is being written, I have just searched for Gate 22B at the Denver Airport. I then proceeded to search for an electrical outlet, my power cord, the correct port on the laptop, the link to the internet, and so on. These searches are drawn from the subset of total searches for which I have introspective awareness and some memory. We engage in search because there is too much visual information to fully process. Even if the sign for Gate B22 is in my visual field, I still need to use attentional mechanisms to select that object from the welter of other stimuli on Concourse B because attention is required to read that sign (Rayner 1983). Without worrying, for the present, about who this “I” is that is using attention, it makes some sense to imagine that I was asking my search engine to conduct these specific searches. Even if I am not engaged in what seems like deliberate search, covert attention is selecting one object after another, or maybe a few objects at a time, much as the eyes are fixating on one thing after another. The deployments of attention may be based on the bottom-up, stimulus driven salience of the stimulus (Einhauser et al. 2008; Foulsham and Underwood 2008; Koch and Ullman 1985; Masciocchi et al. 2009) (Is that a bottom-up, attention-grabbing bird flying around in Concourse B? Yes, it is! What is it doing in here?). Alternatively, J. M. Wolfe () Harvard Medical School and Brigham & Women’s Hospital, Boston, MA 02115, USA e-mail: [email protected]
M. D. Dodd, J. H. Flowers (eds.), The Influence of Attention, Learning, and Motivation on Visual Search, Nebraska Symposium on Motivation, DOI 10.1007/978-1-4614-4794-8_8, © Springer Science+Business Media New York 2012
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attention might be guided by top-down task demands (Theeuwes 2010), even if those top-down demands do not usually seem to rise to conscious awareness. Consider the searches that could be involved in avoiding obstacles as you navigate down the concourse (Hamid et al. 2010; Jovancevic-Misic and Hayhoe 2009). The obstacles to be avoided might not be the most salient
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