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Cyclical vs. Stochastic Visual Search Models Andrew Elias 11 Aug 2011 NRL Code 7440 branch meeting How a Target’s Effect on the Eye Varies with Distance &

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Eye Tracking Fixations: eye stops (avg. 400 ms) Saccades: jerky eye movements, no data intake

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The Experiment 30 FA18 pilots 72 images 24 distinct maps With/without targets sorted: 3 clutter levels High/low local clutter near target Target:

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Cyclical vs. Stochastic Visual Search Models Cyclical: avoid re- examining things Stochastic: don’t worry about re-examining things

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Disclaimer: Examination Radius (parameter) chosen to make Stochastic model fit the best

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…now choose parameters to make Cyclical model fit the best

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Conclusion Stochastic model is correct. (at least for the majority of our trials)

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Further Research Comparing clutter levels or pilot experience levels: do models/parameters change? Using model parameters as a new measure of global clutter (!!!) or pilot skill Analyze subjects/maps individually to see if some use/allow Cyclical model.

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How a Target’s Effect on the Eye Varies With Distance Purpose: fixation “size” small?large?fuzzy?

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How long are saccades?

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At what distance does saccade length change? 120 px 55 px Map Edge

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Successful Saccade (n.) a saccade which ultimately brings the subject closer to the target

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Seeing or remembering P(Success) P(Success | Not Seeing) Distance to Target (px) P(Seeing)

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“Bayesian” derivation of P(Seeing)

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Successful Run-of-Saccades L : the number of saccades into the future that we observe

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Conclusions 55 px is the threshold for glance-away saccades Attention-grabbing radius may be fuzzy (at least for a large group), but probably spans a subset of the the 55- 450 px zone. Maybe ~120 px These values may be target-dependent and map- dependent. –‘450 px’ value is especially map-dependent. Reaction “time” is less than two saccades.

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a visualization: 44 (±3) px/deg

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Further Research Remove all after-target fixations and see if 2 nd bump disappears, and if 1 st bump gets clearer Blend distributions to model the control-group function

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Acknowledgments Maura Lohrenz, 7441 section head Melissa Beck (LSU) Todd, Stephanie, Mike, Jeremy fellow students! experiment participants

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somebody ask a question!

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The end

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Some initial readings…

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