Change Blindness


  • [Required] Tye (2009) Consciousness Revisted MIT Press. Ch.7. [intranet:tye-changeblindness.pdf]
  • [Recommended] Ned Block (2007). Consciousness, Accessibility and the Mesh between Psychology and Neuroscience. In Behavioral and Brain Sciences 30, pp. 481-548. link
  • [Recommended] Fred Dretske (2007). What Change Blindness Teaches About Consciousness. Philosophical Perspectives 21 (1):215–220.
  • Daniel Simons & Ron Rensink (2005). Change Blindness: Past, Present, and Future. Trends in Cognitive Sciences 9: 16-20.
  • Christof Koch & Naotsugu Tsuchiya (2007). Attention and Consciousness: Two Distinct Brain Processes. Trends in Cognitive Sciences 11:16-22.
  • Christopher Mole (2008). Attention in the Absence of Consciousness? Trends in Cognitive Science 12 (2):44.
  • Christopher Mole (2008). Attention and Consciousness. Journal of Consciousness Studies 15 (4):86-104.
  • "Did you see the unicycling clown? Inattentional blindness while walking and talking on a cell phone" from Applied Cognitive Psychology

The experiments

  • Change blindness - Failure to notice large changes to the visual scene.
  • ChangeBlindnessExamples - flicker, slow changes, swaps
  • Tye's question - Do subjects (consciously) see the items that have changed?
    • blindness vs inaccessibility
  • Inattentional blindness - Failure to notice prominent items in the visual scene.

The theories

Relevance - the nature of consciousness, connection to attention.

Why is that the case? According to some psychologists and philosophers (the sparse theory):

  1. We do not see the changes.
  2. We see only those things we pay attention to.
  3. We think we see everything in the visual field, but it is an illusion.
  4. Our visual experience is much sparser than is commonly supposed.

The proposal is counter-intuitive. We normally think we see more than what we focus our attention on because:

  1. it seems to us that we see all the details.
  2. we can attend to any area of the visual field and report what we see.
    • Reply - But it might be a case of the refrigerator light illusion.
  3. if we only see what we attend to our visual experience will have gaps.
    • Reply - Visual representations can leave things out by underrepresenting and misrepresenting.

Simons and Rensink: Must rule out these alternatives:

  1. Complete representations exist, but decayed before change perception.
  2. Complete representations exist, but not accessible to change detection mechanisms.
  3. Complete representations exist, but not the right form for change detection (same as above?)
  4. Complete representations exist, but change detection processes have not been engaged (even though they could have).

Note - The different cases might have different explanations.

  • Slow changes might be a failure of memory.
  • Flicker cases might be different.

Against the sparse theory

Landman et. al.

See discussion in Block and Tye.

  • Results: Bad performance for the first task; near 100% correct for the other two.
  • Lamme: The sparse theory is wrong. The role of attention is to get conscious information into (globally accessible) stable working memory.
  • Tye's reply: Information about the orientation was represented in the visual system. But it does not follow that we were consciously aware of the orientation of each of the rectangle.


Can you notice the difference between the two:

you would if the extra brick looks like this

According to Dretske, (a) we know on the basis of how the bricks look to us that none of them are blue or tilted. And ... (b)

@It was, in part, the way Sam looked to you that told you that none of the bricks were blue or tilted.@

Tye objects to (b) but not (a).

Discuss: But how can (b) be true without (a) being true?