4. Perception

Lesson 1

• Empiricism• Common-sense realism• Perceptual illusions

Perception

“awareness of things through our 5 senses”

Choose a sense to lose!

Choose a sense to lose!

• Which sense did you choose? Why?• Which sense is most identified with

knowledge? Why?

Empiricism

All knowledge is ultimately based on perceptual experience

The subjects you study?

Can you list the role perception plays in your different IB subjects? Are there any areas of knowledge where perception plays NO role?

Common-sense realism

Perception is passive and gives us an accurate picture of reality

Do you think our senses give us an accurate picture of how the world really is?

http://www.grand-illusions.com/opticalillusions/impossible_motion/

Perception is a complex process

Sensation and interpretation

Interpretation: Context

Interpretation: Expectations

Interpretation: Expectations

• The following four slides will be shown very quickly. Try to remember what the four cards are.

Can you name them?

Can you name them?

Illusions from other senses?

Can you think of any illusions from our other senses?

Perceptual illusions

Pass the two blocks around. Which one is colder?Put ice cubes on the blocks and watch

Perceptual illusions

How did your sense of touch score?!

Lesson 2

• Selectivity of perception• Seeing and believing• Distinguishing appearance from reality

Selectivity of perception

• Discuss in groups how the following picture would be interpreted through the eyes of a religious figure, a physicist, a painter or a farmer?

Selectivity of perception

• Discuss in groups how the following picture would be interpreted through the eyes of a biologist, logger, environmentalist, a native American?

Selectivity of perception - emotionThere’s

someone for everyone.

Seeing the world clearly?

In what emotional state do we see the world clearest? Why?

Selectivity of perception - education

What do you see? What would a doctor see?

Selectivity of perception - education

What do you see? What would a musician see?

Selectivity of perception - education

What do you see? What would a dentist see?

Selectivity of perception - education

What do you taste? What would a wine expert taste?

Seeing/believing

• In the 19th century scientists believed there is a planet between Mercury and the sun. Some believed it so much they said they had seen it in their telescopes. No such planet exists.

Seeing/believing

Seeing/believing

Seeing/believing

Seeing/believing

• YouTube - Godless Comedy from That Mitchell and Webb Look

Eye witnesses

• YouTube - Impossible eye witness funny sketch - A Bit of Stephen Fry & Hugh Laurie – BBC

• YouTube - The Eyewitness Test: How do you stack up?

Distinguishing appearance from reality

How can we trust our senses?

Confirmation by another sense

It looks like poo, it smells like poo. I’ll

taste it just to make sure.

Coherence

Independent testimony

Lesson 3

• Extension of the senses• Ultimate reality• What is really out there?• Theories of reality• What should we believe?

Extension of the senses

Electromagnetic spectrum

λ ≈ 700 - 420 nm

λ ≈ 10-7 - 10-8 m

λ ≈ 10-9 - 10-11 m

λ ≈ 10-12 - 10-14 m

λ ≈ 10-4 - 10-6 m

λ ≈ 10-2 - 10-3 m

λ ≈ 10-1 - 103 m

Ultrasound

What is really out there?

What is really out there?

• Does the “sweetness” exist in the coke or only in your mouth?

What is really out there?

Where is the green in the grass? In the grass or in your eye (or brain?)

If we had evolved differently, sensitive to electromagnetic radiation of different frequencies we would not see grass as green at all…….in conclusion the world really has no colour at all!

What really is out there?

If a tree falls in a forest, and nobody is there is hear it, does it make a sound?

Two types of sound?

• Physical – vibrations in the air• Experienced – the sound we hear/experience

in our brains

No experienced sound before life on earth?

A rose with no colour?

Does anything exist independent of our experience?

Theories of reality

Common-sense realism

The way we perceive the world mirrors the way the world is

Can you outline the main arguments against common sense realism?

Scientific realism

The world exists as an independent reality, but very different from how we perceive it.

Phenomenalism

This comes from empiricism. We cannot say there are tables in a room, only that if we go into a room we will have various table experiences!

The world does not exist

independent of our experience

of it

Phenomenalism

If you believed in phenomenalism, what difference would it make to your practical life?

The world does not exist

independent of our experience

of it

Are you bothered?Does it bother you that we can’t know anything about what the Universe is like independent of our existence of it?

Quotation walk

• Around the lower school corridors are posted various quotations about perception. Choose one as a starting point for your next TOK essay. Explain what the quotation means, link it to at least two IB subjects you are studying, and link it to at least two experiences from your own life. Due ………………