Stimulate Onset Asynchrony (SOA) – the time between one stimuli onset and a second stimuli onset • Target Template- mental display of where the searching target may be found • Top-down Guidance- using previous experience, existing knowledge, or the context to search for a target • Salient Scene Region- the part of a visual field that may “pop-out” and draw attention Definitions Background
Eye movement guidance • Image features • Cognitive knowledge • What determines where we direct our eyes? • Salient scene regions • Fails in real-world scenes • Top- down guidance • Using previous experience, context to guide search • Target template • Mental representation of the target Previous Studies Background Visually Salient Scene
Limitations of Previous Research Previous research demonstrates that target template’s specificity affects real-world visual search performance Shorter RTs for picture cues than word cues What is the role of target template’s specificity on eye movements during the search process?
Real World Search • Abstract Cue (word) OVEN MITT • Specific Cue (visual)*
Research Question • This study investigates how target template’s specificity affects real world search • What subprocesses does target cue affect? • Target template set up time • Activation map • Speed of comparison processes
Present Study: Measurements • In order to reveal the effect that target template specificity has on the search process, Malcolm and Henderson divided search into three behaviorally defined epochs • Search initiation time • Scanning time • Verification time
Present Study: Manipulations • Cue • Picture (specific) • Word (abstract) • SOA • - Long • - Short *
Present Study: Measurements • Number of Regions visited during Scanning • Measures activation map’s selection of target-probable regions • Improved activation map results in fewer regions viewed
Present Study: Measurements • Mean Scanning Fixation Duration • Measures process of matching fixated object to an internal representation • Faster processing results in decreased fixation duration
PredictionsIf more specific cues benefit… • …visual search, then total trial duration should be reduced. • …target template set-up, initiation time should be shorter than word cues with short SOAs. • …activation map’s selection of target probable regions, then fewer regions will be fixated on during scanning . * • …comparison processes, then mean scanning fixation time should be shorter. *
First Experiment • The purpose of the first experiment was to show if cue type and/or SOA benefit or affect visual search • Method: • 12 participants • 60 picture cues and 60 word cues • 60 real-world scene photographs with search targets • Subjects eye movements tracked with eye-tracker equipment • Word or picture cue shown on screen • Photograph then shown after SOA times of 300 and 1000 ms • Participant asked to locate target as quickly as possible and press response key when target was found
First Experiment: Results • Faster response times for picture cues than word cues • Search was facilitated by ability to establish a more precise target template • Scanning and verification times shorter for picture cues • Advantage for more precise target template • SOA failed to influence total trial duration • However, search initiation time was faster given longer SOA • Supports research stating that responses are faster given more warning time to prepare
Second Experiment • Why the second experiment? • Previous research claimed that specific cues reach their full advantage with longer SOAs • Shorter SOA may have been too long to reveal effect • Method: • 13 participants • Same methods as previous experiment with SOAs of 200 or 800 ms
Second Experiment: Results • Trial duration again faster for picture than word cues • Pattern of results were identical to Experiment 1 • Reduced SOA failed to produce a main effect
Third Experiment • Why a third experiment? • A possible explanation of the null effect of the SOA could be related to the familiarity of the targets. • In previous studies, subjects had been familiarized with the cues. • If failure to find evidence for varying target template set up time was due to lack of familiarity with the pictorial properties, then this experiment should show interaction between cue specificity and SOA.
Third Experiment: Method • 15 participants • Same procedure as the first 2 experiments • SOA time was reduced again to 125 ms along with the 800 ms • Participants shown all possible target pictures four times each prior to experiment • Materials that were believed to be too easy (ceiling effect that might mask SOA effect on scanning) replaced with more difficult scenes
Third Experiment: Results • Data analyses mirrored the first two experiments • Even with familiarization, SOA only affected general preparatory processes. • Results seem to be consistent with hypothesis that search initiation time reflects general preparatory process rather than time needed to set up target template
Hypothesis Review • Conclusions • Again, looking for, “What guides eye movements during search?” • This study looked at how target template specificity affected the search process • Results DID support that a target template CAN guide real-world search • Top- down manner • Agrees with other findings that picture cues used less fixation duration than word cues
Improvement • Conclusions • An actual study containing depth • Current study had 2-D real- world scenes • What about the actual 3-D real- world?
Possible Future Studies • Conclusions • Present study = effect of target template specificity in isolation • Future study = effect of target template specificity with 2 or more information sources • More beneficial for real- world search • Guided search model does NOT explain how attention is distributed • Real- world search model • Must integrate fixation durations • Distribution of attention changes