Download - Kelly Shen and Martin Par é
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“Nothing average ever stood as a monument to progress. When progress is looking for a partner it doesn't turn to those who believe they are only average. It turns instead to those who are forever searching and striving to become the best they possibly can. If we seek the average level we cannot hope to achieve a high level of success. Our only hope is to avoid being a failure.”
- A. Lou Vickery
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Guidance of Eye Movements During Visual Conjugation Search: Local and Global Contextual Effects on Target Discrimination
Kelly ShenandMartin Paré
Presented by:Jason Chanfor joeLAB
July 15,2008
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Introduction
• Attentional resources required for analysis of visual images
• Focal attention not important for feature search tasks, is important for conjunction search tasks
• Previous studies did not measure spatial allocation of attention; detailed information can be derived from eye movements
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Key Questions
1. Are visual search strategies influenced by composition of stimuli?
2. Are visual search strategies influenced by arrangement of stimuli?
3. Is the timing of an initial saccade influenced by target discriminability?
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Methods
• 3 female rhesus monkeys• Magnetic search coils or infrared camera• Primate chair
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8-stimulus display
Adjacent distractor randomized
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12-stimulus display
Colour-similar to colour-different distractor ratio randomized
0:11 ratio
Feature search based on colour
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12-stimulus display
Colour-similar to colour-different distractor ratio randomized
8:3 ratio
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12-stimulus display
Colour-similar to colour-different distractor ratio randomized
11:0 ratio
Feature search based on form
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Results – Conjunction characteristics
• Conjunction less efficient than single feature• Longer search time for conjunction due to
increased # of saccades, not delayed response• Conjunction task only involved attentional
resources for saccade production
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Results – Local contextual effects
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Results – Local contextual effects
# of colour changes in display had no effect on accuracy or search time
Target colour = attentional bias
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Results – Global contextual effects
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Discussion – Display composition
• Flanking task effect: less visual processing necessary to identify stimulus
• Masking effect: deter identification of target
• CTVA (CODE theory + visual attention) account for local contextual effect
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Discussion – Visual guidance
• Colour guiding feature for target search, esp. when proportion of same-colour stimuli low
• Search strategy = target-feature + salience
• Strategy not guided by only bottom-up
• Colour more discriminable than form
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Discussion – Initial responses
• Initial responses from automatic process
• When & where based on limited visual information processing from display
• Visual processing limited: attentive scanning has limited opportunity to occur
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1. Search strategies influenced by composition of stimuli?
• YES
2. Search strategies influenced by arrangement?• YES
3. Timing of an initial saccade influenced by target discriminability?
• NO
Conclusion
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THE
END
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Next Week @ Journal Club:
McCOLLOUGH EFFECT
the