Cornell Psych 1101 Day 12: Sensation & Perception

The Problem Of Perception

P S YC H 1101 : DAY 11 P ROF. DAVID P IZ AR RO CO R NE L L P S YC H . NE T

Exam Stuff • • • •

Chapters 1-6 (but chapter 5 questions will be only about what I cover today)!

Chomsky reading!

Lectures up to today!

25/25 Lectures/Readings

How Do We Acquire Knowledge About The World?

Sensation •

We acquire basic sensory information (we detect “distal” objects in the world) through the senses:!

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taste! touch ! smell! hearing! vision!

Brain transduces incoming information (e.g., light waves, sound waves, particles)

Are My Sensations The Same As Yours?

Not Necessarily: The Case Of Taste

Perception •

Putting sensory information together to represent the external world is what we mean by perception!

• •

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Identification (what am I seeing?)!

Categorization (what kind of thing is it?)!

How does basic sensory information turn into mental representations?

Objects and people: Where they are and what they are doing

Perception Is A Difficult Problem •

The mind uses a number of tricks in order to make sense of all of the incoming sensory information!

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Visual perception!

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Our mind makes certain assumptions about the environment to help us see accurately despite having limited data to work with!

• • •

Color!

Objects!

Depth

Color

A Simple Assumption • Shadows make surfaces darker!

• When we see a surface in shadow, we automatically assume it is lighter than it looks!

• So we see it as lighter !

• But when you remove cues to shadow, we see it as it really is

Objects

Depth

Depth Perception • One of our more important perceptual abilities involves seeing in three-dimensions!

• Depth perception is difficult because we only have access to two-dimensional images!

• How do we see a 3-D world using only the 2-D retinal images?

Depth Perception Cues • Stimulus characteristics that influence our perceptions! • We are able to see in 3-D because the visual system can utilize depth cues that appear in the retinal images.

Size-Distance Illusions • In each of these examples, the top and bottom lines are actually the same length.!

• In each case the top line looks longer.!

• Why?

(A ) MÜ LLER -LY ER ILLU SI ON

(B ) P ONZO ILLU S ION

Muller-Lyer Illusion • Perceptual psychologists have hypothesized that the top horizontal line looks longer because it also looks farther away.! • Specifically, the inward pointing arrows signify that the horizontal line is closest to you, and the outward pointing arrows signify the opposite case.

Ponzo Illusion • Converging lines indicate that top line is farther away than bottom line