1. Attention & Change Blindness

2. What is attention? How is the word used? Examples:
something bright caught my attention
I didn’t see you, I was paying attention to the game
I struggled to pay attention to the lecture
I don’t remember even cleaning the table, I must not have been paying attention
Attention refers to many different kinds of mechanisms

3. Attention and limits on information
We need attention to limit the amount of information that is processed
Why are there limits on the amount of information we can process?

4. Attention and limits on information
Human information processing is massively parallel, up to a point  Serial bottleneck
limited sensory systems
limited effector systems
movements must be planned sequentially
words can only be spoken sequentially
After bottleneck, it is the allocation of our attention that determines what is analyzed
Often, we are unable to process information that is unattended  inattentional blindness

5. Magic trick to Demonstrate Inattentional Blindness
Please choose one of the six cards below.
Focus on that card you have chosen.
Best way to demonstrate inattentional blindness is by performing a quick magic trick.
If you have seen it before don’t spoil it for those that haven’t!
Choose one of the six cards below.
Really focus on that card you have chosen.

6. Can you still remember your card?
Magic trick (2)
I’ve shuffled the cards and removed the one which I think was your card.
I’ve shuffled the cards and removed the one that I think was your card.
Can you still remember what your card was?
Keep focusing on that card.
Can you still remember your card?

7. Here are the remaining five cards, is your card there?
Magic trick (3)
Here are the remaining five cards, is your card there?
Okay here are the five remaining cards.
Is your card there?
Nope then I must have got it right.
Now what is the probability that all the people in this room choose the same card –
very little so how did I do it?
Did I guess right? Or is it an illusion?

8. Magic trick – The Explanation
You just experienced Inattentional Blindness
None of the original six cards was displayed!
You just experienced inattentional blindness.
When I asked you to select a card you were focusing your attention onto that single card.
Thus you suffered inattentional blindness to the other cards.
When the remaining five cards were shown you immediately looked for your card only - and it's not there.
How -
None of the original six cards are there
but due to inattentional blindness you didn't attend to the other cards
and therefore can't remember them to check against the five remaining cards.
Thus it looks like only your card was missing!

9. Inattentional Blindness
Attention involves selective processing of visual information
Sometimes, we seem unaware of the selectivity: inattentional blindness
Lots of demos:
Airplane demo
Dinner demo

10. Some of these demos are from: Simons & Levin, 1997, TINS, 1, 261-267

11. Inattentional Blindness
Why is it hard to notice the change (initially)?
When motion detection is disrupted, it is very difficult to observe changes to unattended image locations
Brain makes reasonable assumption that things do not change unexpectedly (in the absence of motion cues).

12. DVD Demo of basketball players
Task: count the number of times the white team passes the ball to each other
Important to pay close attention to task
(Simons & Chabris, Perception, 1999, 28, 1059 – 1074)

13. Other demo’s
    Dan Simons (University of Illinois):
see also letter task:

14. Inattentional Blindness
Results demonstrate:
Remarkable gaps in our perception
Human’s interpretation of the visual field is much sparser than the subjective experience of “seeing” suggests
Perception of objects requires considerable effort / resources – Attention is needed to see the change
If attention is elsewhere (even temporarily), changes can be missed  implication for drivers?

15. The role of similarity
Percent of participants detecting unexpected objects as a function of similarity between their luminance or brightness and that of target objects. From Most et al. (2001)

16. Role of prior attention to the object
Percent correct change detection as a function of form of change (type vs. token) and time of fixation (before vs. after change); also false alarm rate when there was no change. From: Hollingworth and Henderson (2002).

17. Selective Attention

18. Focused Auditory Attention
Colin Cherry
The cocktail party effect
Cherry (1953) found that this ability involves using physical differences to maintain attention to a chosen auditory message
Moray (1959)
Unattended auditory information receives practically no processing

19. Dichotic listening/ Shadowing tasks

20. Dichotic listening demo
Focus your attention on (or shadow) the left ear, and try to remember only the details in the left ear.
Quiz:
1. John ate breakfast with his father True False
2. A man shook his head and frowned. True False
3. Birds were singing when John awoke. True False
4. Miles Davis was singing when John awoke. True False
You probably recall the facts from the left ear's dialog much better than those of the right ear; you may not remember any of the right ear's dialog!

21. What gets through? What happens to unattended message?
Not much, we seem to remember mostly low-level information (human voice or not, changes in gender, not a change in language)
(Colin Cherry)
 Subjects names get through (30% of the time)
The same word can be repeated without being noticed
(Moray, 1959)

22. Broadbent’s Filter Theory
Sensory information is processed until a bottleneck is reached
One of the inputs is then allowed through a filter on the basis of its physical characteristics, with the other input remaining in the buffer for later processing
Early selection theory (select message by ear)

23. Some semantic processing though in unattended ear …
People notice their own name at parties
Treisman experiment:
 Problem for early selection theories

24. Treisman’s Attenuation theory
Messages are attenuated but not filtered on the basis of physical characteristics
Semantic criteria can apply to all messages, attenuated or not
Semantic criteria are harder to apply to attenuated messages, but still possible

25. Deutsch & Deutsch Late Selection theory
Capacity limitations are in response system, not the perceptual system
All information is processed completely unattenuated

26. Critical Experiment (Treisman & Geffen, 1967)
Asked to shadow one ear and tap a button when a certain word is heard in either ear, people do much worse at word detection in unshadowed ear.
 against late selection theory

27. Selective Visual Attention

28. Location-based Attention
Posner (1980)
Attentional spotlight: a theory which holds that we can move our attention around to focus on various parts of our visual field
The spotlight can span varying degrees of visual angle
Erikson & St. James (1986): zoom-lens model

29. The Cue Validity Task
Posner presented either a central cue or a peripheral cue before a target appeared.
Cues valid on 80% of the trials, invalid on 20% of the trials or vice-versa

30. The Cue Validity Task
When cues were valid, response times were faster than when cues were invalid.

31. The Zoom Lens analogy Spotlight has fixed size
Zoom lens is flexible in size
Experimental subjects can control whether they focus on a specific target (the middle letter of a five letter word) or spread their attention (across all the letters) (La Berge, 1983)

32. Evidence in Favour of the Zoom-lens Model
Mean reaction time to the probe as a function of probe position. The probe was presented at the time that a letter string would have been presented. Data from LaBerge (1983).

33. Experiments Demonstrating Split Attention
Awh and Pashler (2000).
(a) Shaded areas indicate the cued locations and the near and far locations are not cued; (b) probability of target detection at valid (left or right) and invalid (near or far) locations.