Perception, the Brain, and Consciousness

1. Perception, the Brain, and Consciousness Minds and Machines

2. Our Eyes as a Window to the World

3. The Myth of ‘Perfect’ Perception • The myth of perception is that as long as: • Our eyes are functioning properly • We’re not wearing rose-colored glasses • We’re not drugged • We’re not subjected to some visual illusion • We’re not in the Matrix • … (other exceptional/rare situations) • … we perceive the world exactly as it is. • Wrong!

4. Our Senses are Limited • Our eyes only perceive a very small part of the electromagnetic spectrum; we don’t see infrared, ultraviolet, X-Rays, Gamma-Rays, Micro-waves, Radio-Waves, etc. • Similar for our other senses. • OK, but what we do perceive, is still exactly as it is, right? • Wrong!

5. The Checker Board Shadow Illusion A B

6. The Checker Board Shadow Illusion A B

7. Which Perception is ‘Correct’? • But is it wrong to perceive A to be darker than B? • If it is a chess board, then A really is darker than B in some real physical sense, even if the raw stimulus happens to be the same. • And that’s just it: perception is an interpretation of the raw sensory stimuli. • Perception = f(sensory stimuli)

8. Perception as an Inversion Problem • We can look at perception as an inversion problem: our mind/brain has to figure out what is going on in the world ‘out there’, given the raw incoming sensory stimuli. • But this inversion problem is inherently underspecified: that is, at all times, an infinite number of scenarios can produce the incoming sensory stimuli we get. • Hence, we have to make a guess, i.e. perception is inherently inferential (and non-deductively so!)

9. The Blind Spot X X

10. Color Contrast A B

11. Devils, Angels, Aliens, Jesus, Mary, and … Illinois! Devil Man on Mars Cranky Guy Mary Angel Jesus

12. Expectations, Fears, and Wishes • What we perceive is effected by: • Our expectations • Corridor Experiment • Our fears • Person in the shadow • Our wishes • St. Nick • And probably many other states of mind

13. Summary:Perception is Constructive! • At all times, how we perceive things is a construction of our mind (brain). • Perception = f(raw sensory input, attention, beliefs, expectations, …) • A very complex function! • It is estimated that about a third of our brain is dedicated to visual processing alone!

14. Why Perception Doesn’t Feel Constructive • Two big reasons: • We are, under normal circumstances, getting a lot ‘right’ • I rarely get contradicted in my constructions of reality and how I subsequently act on that • We consistently perceive the world in the same way (i.e. we’re stuck in Plato’s cave) • But what if things go wrong? • Video discusses interesting cases of brain damage revealing pretty strange perceptions

15. Some Philosophical Questions • Is the ‘self’ a mere perception? • So what are things really like? • How is knowledge and science possible? • How do I know what it is that you perceive? • Do you have any conscious perceptions? • Do animals and machines have any conscious perceptions?

16. Perception of ‘Self’ • We don’t just perceive the outside world. • We also perceive things about our self • Interoception (hunger, pain) • Proprioception (balance, body posture) • But again, what we perceive about our self is a construction of our self • Video: Phantom Limb Syndrome • Video: God Syndrome • Is the self a mere construct?

17. What is Really out there? I see a tree ?

18. What do You See? I see a tree ?

19. Invertoids I see a tree ?

20. Weirdoids I see a tree

21. Who’s the Invertoid? I see a tree ?

22. ‘Publicly Observable’ 1 tree E = mc2 !

23. The Puzzle of Consciousness • Some brain activity ‘leads to’ conscious experiences, but other activity does not. Why? • Indeed, if we can process so much visual information unconsciously, why do we have any conscious visual experiences at all??

24. Zombies I see a tree!

25. The Zombie Paradox I have a conscious experience of seeing a tree

26. Blindsight I don’t have any conscious experience, but I think there is a tree

27. Blindsight and Animal Consciousness • Blindsight is often explained by pointing to the fact that there are two neural pathways from our eyes to our visual processing centers in (the back of!) our brain: one evolutionary old pathway (through the brain stem), and one new (through the thalamus) • Does this mean that animals without the new pathway do not have conscious experiences? • And again, why does one pathway lead to conscious experiences and the other not?

28. Materialist Theories of Consciousness • Consciousness is: • quantum collapses in microtubules internal to neurons (Penrose, Hameroff) • thalamically modulated patterns of cortical activation (Llinas) • left hemisphere based interpretative processes (Gazzaniga) • emotive somatosensoryhemostatic processes based in the frontal-limbic nexus (Damasio) • synchronous neural oscillations at 40-70Hz (Crick, Koch) • spatiotemporal patterns in electro-magnetic field produced by brain (McFadden, Pockett) • global workspace of cognitive activity (Baars) • integrated information (Tononi)