Searching in the Dark: Cognitive Relevance drives attention in real-world scenes

1. Searching in the Dark: Cognitive Relevance drives attention in real-world scenes J.M. Henderson, G.L. Malcolm, & C. Schandl 2009 Emily, Ben, and Caitlin

2. Background Visual Salience Hypothesis-bottom up processing-we look at scene locations on the basis of image properties Cognitive Relevance Hypothesis-top-down control-knowledge about the tasks influences visual attention Region of Interest (ROI)-rectangular areas around key objects in scene (salient or target object)

3. Past Research • Past research has supported both hypothesis • Henderson, Weeks, and Hollingworth, 1999. • Henderson, 2003. • Used an algorithm formulated by Itti and Koch (2000) that determines salience in images

4. The Question: • Does visual salience or cognitive relevance guide our visual search? • If the Visual Salience hypothesis is true: • Gaze will be captured by the most salient ROI • Finding target item will be more difficult if not salient • If cognitive relevance hypothesis is true: • Should be able to ignore salient objects if not the target item

5. Methods • 24 participants (12/experiment) • 60 scene photographs • 22/24 critical scenes in Experiment 1 and 2, respectively • In critical scenes, the targets were non-salient while scene contained highly salient ROIs at other locations • Search target appeared in semantically appropriate locations • In noncritical scenes, targets items were salient • Eye tracker used to monitor movements of right eye • Participants were cued for target items with either an image or word cue

6. Methods

7. Procedure • Central Fixation • Cue • Word or image • Image cues were exact images of search targets • Scene appears • Participants were asked to find target as fast as possible and to press a response key

8. Experiment 1 vs. Experiment 2 • In Experiment 1, participants were familiarized with the target items before the search trials • In Experiment 2, no familiarization process occurred • This was to explore the possibility that visual salience can be overridden by feature similarity to a search template in memory • Or that, salience takes control in situations of unfamiliarity with targets

9. Results Target ROIs were fixated a much greater proportion of trials than salient ROIs Target ROIs were fixated first far more often than salient ROIs Results exhibited the same pattern for both experiments

10. Results, cont.

11. Discussion • Toward a Cognitive Relevance Theory • Knowledge-based control • Potential saccade targets are ranked based on relevance to the task • Mental creation of object based map • Likely a 2-D image • Figure-ground Distinction made and ranking applied to objects in map • Attention is guided to regions based on the ranking

12. Discussion, cont. Visual salience is used to help create the map, but cognitive ranking directs our attention

13. Conclusions • The experiment doesn’t really hit on unfamiliarly—uses familiar objects and scenes • Fails to measure salience in an unfamiliar scene • Detective Work • Future Work: • Search tasks involving novel objects rather than everyday objects • Would salience be more of a factor?