1. Attention

2. Looking without Seeing

15. Why Have Attention? Limited resources –Too much information Attention: 1. selects important/relevant information 2. modulates it in the context of the task at hand

16. Attention Mechanisms Top-Down –Goal-driven Bottom-up –Stimulus-driven (“attention capture”) –There is debate if total bottom-up really exists Attention capture is shown to be modulated by task goals Early Selection vs. Late Selection

17. Visual Attention © Stephen E. Palmer, 2002 Evidence for Early Selection in Audition Shadowing paradigm What can be followed? Position (left/right)? Pitch (male/female)? Language (English/French)? 15.1 + + X --> Early Selection

18. Visual Attention © Stephen E. Palmer, 2002 Evidence for Late Selection in Audition Cocktail Party phenomenon Unselected information can get in: Subject’s own name Words expected from context --> Early and late selection 15.1

19. Visual Attention © Stephen E. Palmer, 2002 Inattention Paradigm (Mack & Rock) What do we see without attention? 15.1

20. Visual Attention © Stephen E. Palmer, 2002 Inattention Paradigm Results: 15.1

21. Visual Attention © Stephen E. Palmer, 2002 Inattentional Blindness: 15.1 On many trials, subjects report seeing NOTHING if the test object is at fixation. Square at Fixation: 50-75% IB Own Name at Fixation: 5% IB Other’s name at Fixation: 35% IB Variant of own name at Fixation: 60% IB (e.g., JECK instead of JACK)

22. Show movie…

23. Visual Attention © Stephen E. Palmer, 2002 Change Blindness 15.1

24. Visual Attention © Stephen E. Palmer, 2002 Change Blindness 15.1

25. Eye Movements Q: Why? A: Limitations of the eye – only fovea is high-res enough for many tasks Two types: –Saccades Rapid motion (25-30 ms) between fixations Saccades occur every 250-300 ms Also evidence for “micro-saccades” –Smooth-pursuit (tracking) movements Require feedback

26. Eye-Tracking Alfred Yarbus

27. goal-attenuated Alfred Yarbus

28. Saliency Maps Itti et al proposed that bottom-up attention can be predicted from low-level visual features. Eye-tracking can be used to validate the predictions What are the problems with this idea?