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When Does Repeated Visual Search in Scenes Involve Memory? (2011)

When Does Repeated Visual Search in Scenes Involve Memory? (2011). Melissa L-H. Vo & Jeremy M. Wolfe. Quinn, Chelsea, Christine. Background. Knowledge about a given scene can speed search within the scene…

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When Does Repeated Visual Search in Scenes Involve Memory? (2011)

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  1. When Does Repeated Visual Search in Scenes Involve Memory? (2011) Melissa L-H. Vo & Jeremy M. Wolfe Quinn, Chelsea, Christine

  2. Background • Knowledge about a given scene can speed search within the scene… • This study aims to understand the acquisition of that knowledge and the role memory plays in scene searches.

  3. Previous Research has shown: • Observers can remember both the spatial context of a scene & the specific positions of the local objects after prior exposure to a scene. (Hollingworth) • Observers may not use always use memory to make a search more efficient, such that when recalling objects, it turns out to be more efficient to search the same scene again rather than reactivating stored display representations. (Kunar, Flusberg & Wolfe)

  4. Previous studies have had observers perform search tasks in novel scenes for each trial. • This study has observers perform multiple search tasks in the same scene, while recording eye movements.

  5. Hypothesis & Predictions That merely looking at objects does not speed search for these objects in later searches

  6. Purpose These experiments were performed in order to find out if memory played a role on visual search

  7. Experiment 1: Method • There were 3 blocks • Observers searched for 15 different objects in the same scene • There were 10 scenes • They did 150 searches per block

  8. Experiment 1 • Observers had 15 trials, and on each trial they were tasked with finding a different object on each trial • Observers then did the same 15 trials again per block • This was done in order to see if their search for the object was faster after having found the object already the first time

  9. Experiment 1: Visual aid

  10. Experiment 2: Methods • Block 0 • Observers had 15 random letters superimposed over future targets • A letter was cued for observer to search for that letter • 15 trials, each letter cued and searched for once 10 different scenes • 150 trials

  11. Experiment 2: Visual aid

  12. Experiment 2: Methods • Blocks 1 and 2 were similar to experiment 1 • Block 0 was necessary to see if the target letters the observers were searching for cued future targets to the observers

  13. Experiment 2 • Observers were tasked with locating letters in a scene that were superimposed over objects that would later become search targets • This was done in order to find out if the preview of a future target will influence search speed while observers are unaware that the preview will be a future target

  14. Results- Experiment 1 • Quick Review: • 15 different objects • Across a single unchanging scene • Each item 3x (1/block) • How the data was organized: Time to first fixation Block 1 750 • 3 epochs • searches 1-5 • searches 6-10 • searches 11- 15 • 3 blocks • Block 1 • Block 2 • Block 3 Block 2 500 msec 250 Block 3 1 2 3 Epochs

  15. Results- Experiment 1 • No main effect of search epochs • Significant search improvement when observers search for the SAME object from Block 1, again in Block 2 and Block 3 • Target fixation dropped 300msec from Block 1 to Block 2 • Only dropped 50 msec from epoch 1 to epoch 3 all within Block 1 Time to first fixation Block 1 750 Block 2 500 msec 250 Block 3 1 2 3 Epochs epoch 1: searches 1-5; epoch 2: searches 6-10; epoch 3: searches 11-15

  16. Discussion- Experiment 1 • Memory for previous search targets reduces chance of refixating on these objects when searching for a new target • Object Information  During Search ≠ functional for guiding initial searches HOWEVER…

  17. Discussion- Experiment 1 • Evidence for memory guidance when the search target is repeated • By Block 3, search appears to be guided by search target memory • First saccade goes to target (generally)

  18. Results- Experiment 2 “But what happens if an object shared the location of an earlier search target, but was not the search target itself?” “When that object later became the search target would we observe a search benefit from having looked at the shared location?”

  19. Experiment 2: Visual aid

  20. Results- Experiment 2 • Block 1 of Exp. 2 similar to Block 1 of Exp. 1 • Previous scene exposure during letter search did NOT speed search for objects Time to first fixation Exp 1 750 Block 1 500 msec 250 Block 2 1 2 3 Epochs

  21. Discussion- Experiment 2 • Block 0 = average 30sec exposure to scene w/ fixation of the location of an eventual target object • ^ Produced NO transfer to search task • If only looking at an object, it does not automatically create a representation that can guide search

  22. Drawbacks? • Letters hiding targets too much? • Letters becoming a distraction? • Letters overpowering the actual background scene of the image?

  23. Possible Future Studies… • Instead of just repeatingobjects… • How many times does one need to view the object before the location is set to memory? • And for how long?

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