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:!
• • • • •
•
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!
• •
•
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!
•
Visual perception!
•
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