“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

Guidance of Eye Movements During Visual Conjugation Search: Local and Global Contextual Effects on Target Discrimination Kelly Shen and Martin Paré Presented by: Jason Chan for joeLAB July 15, 2008

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

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?

Methods 3 female rhesus monkeys Magnetic search coils or infrared camera Primate chair

8-stimulus display Adjacent distractor randomized

12-stimulus display Colour-similar to colour-different distractor ratio randomized 0:11 ratio Feature search based on colour

12-stimulus display Colour-similar to colour-different distractor ratio randomized 8:3 ratio

12-stimulus display Colour-similar to colour-different distractor ratio randomized 11:0 ratio Feature search based on form

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

Results – Local contextual effects

# of colour changes in display had no effect on accuracy or search time Target colour = attentional bias

Results – Global contextual effects

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

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

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

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

THE END

Next Journal Club: McCOLLOUGH EFFECT the