1. Selective Attention A tale of bottlenecks and basketballs

2. Two Distinct Processes There are two processes which get bundled into our idea of attention: –orienting - shifting attention (usually in space, but also to non-spatial features such as pitch) –selection - what attention does to perception These are often confused and used interchangeably We’ll switch back and forth between the two, but we’ll try to keep them separate First: the consequences of selection

3. Information Theory: ~1950’s: Psychologists began to think of the human perceptual mechanisms as “information processors”

4. Information Theory: ~1950’s: Psychologists began to think of the human perceptual mechanisms as “information processors” Began asking questions such as “how much information can the human mind handle at once?”

5. Information Theory Donald Broadbent - earliest systematic investigations of selective attention

6. Information Theory Donald Broadbent - earliest systematic investigations of selective attention x x xx oo o o o

7. Information Theory Donald Broadbent - earliest systematic investigations of selective attention

8. Information Theory Donald Broadbent - earliest systematic investigations of selective attention –when simultaneous questions were asked, subject performed poorly on all questions

9. Information Theory Donald Broadbent - earliest systematic investigations of selective attention First principle of human information processing: capacity is limited

10. Information Theory Donald Broadbent - earliest systematic investigations of selective attention

11. Information Theory Donald Broadbent - earliest systematic investigations of selective attention –when simultaneous questions were asked from physically separate speakers, and subject instructed in advance which question to answer, performance was nearly perfect

12. Information Theory Donald Broadbent - earliest systematic investigations of selective attention Second principle of human information processing: information sources can be selected

13. Shadowing Many early studies employed variations on a paradigm called “shadowing” “Four score and seven years ago…” “It was the best of times, it was the worst of times…” “Four score and seven years ago…”

14. Shadowing Many early studies employed variations on a paradigm called “shadowing” –subjects could easily recall details of the shadowed passage but not of the ignored passage

15. Shadowing Many early studies employed variations on a paradigm called “shadowing” –subjects could easily recall details of the shadowed passage but not of the ignored passage –led to the idea that the perceptual mechanisms involve one or more “filters” to shut out unwanted information

16. Stages of Selection Broadbent: Early Selection - a bottleneck exists early in the course of sensory processing that filters out all but the attended channel Alternative theory: Late Selection - the bottleneck exists not at the lowest stages, but at the highest - such as response planning, memory and consciousness

17. Stages of Selection

18. Testing Early Selection Theory - what prediction can be made?

19. Stages of Selection Testing Early Selection Theory - what prediction can be made? Information (such as words) in unattended channel shouldn’t be processed for meaning

20. Stages of Selection Testing Early Selection Theory - what prediction can be made? Information (such as words) in unattended channel shouldn’t be processed for meaning Demonstrates that Early Selection Theory is not entirely correct

21. Stages of Selection Testing Early Selection Theory - what is another prediction that can be made?

22. Stages of Selection Testing Early Selection Theory - what is another prediction that can be made? Should be able to find differences in brain activity in primary sensory areas (A1, V1)

23. Stages of Selection Electrical activity recorded at scalp (EEG) shows differences between attended and unattended stimuli in A1 within 90 ms Hansen & Hillyard (1980)

24. Stages of Selection Evidence exists for both early and late selection mechanisms –One interpretation: early reduction in “sensory gain” followed by late suppression of unselected information

25. Next Time Read article by Anne Treisman