Perception
• We are at the beginning of a new section of the
course. While the first section focused on the
underlying physical/biological basis of our behavior,
the focus of this section will be on our thinking.
• We will start with the input to the process, sensing
the world. This of course was also an issue in the last
section of the course where we saw that behavior
often began with a stimulus that had to be sensed
(think of the knee jerk example, or a taxis).
• Big question: Why don’t we see the world as it is: the
Missouri issue!
Perception
• The nativist-empiricist debate (does all information come in
via the senses or is some innate)?
• Top-down and bottom-up perception and the issue of why
we don't see the world as it is.
• The ear and audition.
• Volley and Place theories of hearing.
• Operating characteristics of the auditory system
• Psychophysics: measuring the response of sensory systems,
including absolute and difference thresholds.
• The just noticeable difference (jnd) and Weber's and Fechner's
law.
• Power functions (Stevens) and its neural counterpart.
Nativism-Empiricism
Empiricists: All information is acquired
via experience, thru the senses
The mind as a blank slate
British movement, John Locke
Nativists: Some information is innate
Nothing in the mind but the mind itself
German movement, Immanuel Kant
The perceptual challenge
• Constructing a perception of the distal
stimulus from the proximal stimulus
• Top-down and bottom-up perception
– Bottom up: start with distal stimulus
(sensory data) and build up representation
– Top down: start with expectations &
context to help sense/interpret incoming
data stream
Automaticity of the process:
The Stroop Effect
Perception
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The nativist-empiricist debate (does all information come in via the
senses or is some innate)?
Top-down and bottom-up perception and the issue of why we don't see
the world as it is.
The ear and audition.
Volley and Place theories of hearing.
Operating characteristics of the auditory system
Psychophysics: measuring the response of sensory systems, including
absolute and difference thresholds.
The just noticeable difference (jnd) and Weber's and Fechner's law.
Power functions (Stevens) and its neural counterpart.
The McGurk Effect
http://www.wimp.com/mcgurkeffect/
Theories of Audition
• Volley Theory (aims at temporal
orientation of auditory sense)
• Place Theory (Von Bekesy)
• Concept of lateral inhibition
Perception
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The nativist-empiricist debate (does all information come in via the
senses or is some innate)?
Top-down and bottom-up perception and the issue of why we don't see
the world as it is.
The ear and audition.
Volley and Place theories of hearing.
Operating characteristics of the auditory system
Psychophysics: measuring the response of sensory systems,
including absolute and difference thresholds.
The just noticeable difference (jnd) and Weber's and Fechner's
law.
Power functions (Stevens) and its neural counterpart.
Pschophysics (Mind-World
Relationship)
• Absolute threshold
• Difference threshold (jnd) = just
noticeable difference
• Weber’s Law
• Weber-Fechner Law
Modified View of all this…
• Magnitude Estimation
• Steven’s Law: Power Function
• Cross Modality Match
Power Functions (vs. Weber)
(r)a = (s)b
• Magnitude Estimation
• Steven’s Law: Power Function
• Cross Modality Match
Visual system characteristics
• Retina: 120 million rods & 6 mill. Cones
• Retinal distribution meaningful
System operating
characteristics
• Color
• Sharpness or acuity: 1 sec. line (1 inch
at 3.5 miles)
• Sensitivity (range (candle at 10 mi. to
noon sun 10,000,000,000,000:1)
• Differential course of adaptation
Duplex Theory of Vision
• Two systems:
– Rod based
• Sensitive
• Low acuity
• Monochromatic
– Cone based
• High threshold
• High acuity
• Color
Adaptation
• Overall range of light 1013 : 1
• Adaptation range of eye 105 : 1
We’re not from Missouri!
• Color Vision ( Perceptual constancies/neural
interactions)
• Feature Detection--the analysis of visual input
– Limulus
– Cats
– Humans
• Top-down perceptual processes and their
interactions with bottom-up
Active processing
• Sentence
• Necker Cube
• Gestalt principles
Brief Story
• The large black dog was chasing the
the pretty little groundhog who was very
much afraid of him across the carpet.
Feature Detection: The
Analysis of Visual Input
Bottom-up perceptual processes (lateral inhibition)
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Limulus (Hartline & Ratliff)
Frogs (Matarana, Lettvin, McCullough & Pitts)
Cats (Kuffler, Hubel & Weisal)
Humans
• Top-down perceptual processes and their
interactions with bottom-up
Top-down processes:
Some examples and a
mechanism
Word Superiority Effect & its Mechanism
Conclusion
• Perception is an active process that
tries to extract a more or less coherent
iinterpretation of the world from the
barrage of stimuli impacting us.
• It focuses on change (temporal or
spatial).
• In order to quickly extract info from the
deluge, it must distort the world to
attempt to see it for what it is!!