2What eye movements tell us…and what they don’t They tell us…areas of interestnumber of fixations for a given timescan patterns and hot spots, etc.They don’t tell us…What information the viewer is extracting upon fixationWhat is happening in the brain whilst the person is viewing a sceneIf perception has occurred
3Distraction and eye movements Increased cognitive workload leads to changes in visual scanning patterns.Tunnelled visionTask demands can dictate visual behaviourIndividuals may be unaware of such changesPeople can look but not see (LBFS errors)
4Driving research How does visual behaviour alter when dual tasking? Do different types of secondary tasks affect eye movements differently?What elements of the secondary task are most distracting?How do we allocate out attention?Can we learn to moderate behaviour?
5Imagery experimentView films from driver’s perspective. Some contained hazards (central or peripheral), some didn’t. Participant had to react when they saw a hazardHalf also completed a secondary, concurrent, imagery task via hands free telephone.Eye movements measuredscan patterns (position of hazard)Variance of fixations in given time frameAreas of interestReaction times for hazardsNumber of hazards reacted toExplain imagery context first.
7ResultsControls detected significantly more hazards than dual taskers (DT).For those hazards they detected, DTs took significantly longer to react than controls.For all central hazards, DTs took significantly longer to react than controlsNo sig difference in RTs between controls and DTs for peripheral hazards……but that’s because the DTs didn’t perceive them!
8Results DTs made significantly more LBFS errors than controls More results based on position of hazard and fixation variance. E.g. when imagery task led fixation away from position of hazard. Sig effects but no time to discuss!
9ResultsSignificant difference in variance of fixations between controls and DTs: controls increased eye movements when a central hazard was presented , DTs decreased their eye movements.Controls showed wider range of fixations.DTs demonstrated visual tunnelling
10Representative examples Undistracted Dual taskingRound up: imagery can selectively interfere with visual perception in a driving scene. Eye movements are affected by increased CWL. Cognitive and visual tunnelling can occur resulting in poorer overall driving performance. Moving on to look at forensic applications using the flicker paradigm shown earlier, along with a change blindness approach to the weapon focus effect.
11Things to consider You get a LOT of data from eye tracking! Need a good sample sizeData collection can take a long time…but it’s worth itNeed really clear research questions from the outsetYou won’t need a lot of the data you collect!Think carefully about how you will analyse your dataBe careful about the conclusions your draw