Some researchers argue that Perception is a biological necessity. Individuals in a coma or persistent vegetative state appear to lack sensation and perception. If you were unable to proce
Some researchers argue that Perception is a biological necessity. Individuals in a coma or persistent vegetative state appear to lack sensation and perception. If you were unable to process and respond to sensory information, what form of perception would you be willing to give up?
Introduction To Perception
Learning objectives: By the end of this presentation you will be able to…
describe the role of bottom-up (sensation) and top-down processes in perception; explain how “perception makes sense of sensory information.”
identify problems that perception must overcome and give examples; recognize these as part of the more general problems of cognition.
By describing top-down processes that make sense of bottom-up (sensory) information, explain the perception of 1) objects, 2) speech and 3) pain
I. Bottom-Up (Sensory) & Top-Down Processes in Perception
EXPERIENCE
PERCEPTION
SENSATION
Bottom-up process whereby
sensory receptors receive
stimulus energy, convert
that energy into neural impulses, and deliver that information to higher levels of mental processing for integration
Top-down process whereby higher-level mental processes
organize and interpret sensory
information; the “mental glue”
that “makes sense” of sensory
information.
Introduction To Perception
Introduction To Perception
II. Problems For Perception
the problems for perception are the problems for cognition generally, that the environment is ambiguous.
example 1: inverse projection problem…
inverse projection problem -problem (faced by the mind) of working backwards from the retinal image to determine the shape of the originating object.
Introduction To Perception
II. Problems For Perception
the problems for perception are the problems for cognition generally, that the environment is ambiguous.
example 1: inverse projection problem…
example 2: incomplete information…
Whose face is this?
Can’t tell? Try looking obliquely; try squinting.
Why would squinting improve recognition? Squinting reduces sensory information.
Reducing sensory information allows perception to play a greater role making sense of sensory information.
Introduction To Perception
II. Problems For Perception
the problems for perception are the problems for cognition generally, that the environment is ambiguous.
example 1: inverse projection problem…
example 2: incomplete information…
Introduction To Perception
III. Examples of Perception At Work
note: look for how top-down processes make sense of bottom-up (sensory) information
A. Object Perception
Can you identify the objects in the following photgraphs?
Caption: “Multiple personalities of a blob.” What we expect to see in different contexts influences our interpretation of the identity of the “blob” inside the circles.
Introduction To Perception
III. Examples of Perception At Work
note: look for how top-down processes make sense of bottom-up (sensory) information
A. Object Perception
B. Speech Perception
Introduction To Perception
speech segmentation- ability to tell where one word ends and another begins even when there is no physical segmentation in the sound energy, as in…
segmentation is dependent on “top-down” interpretation of language (we cannot segment speech in a foreign language)
Introduction To Perception
III. Examples of Perception At Work
note: look for how top-down processes make sense of bottom-up (sensory) information
A. Object Perception
B. Speech Perception
C. Perception of Pain
placebo effect- the decrease in pain from a substance that has no pharmaceutical effect. Due to expectation that the substance will reduce pain.
pain resides in the brain; so does the placebo effect…
Introduction To Perception
Review: For each, what is the top-down process that makes sense of bottom-up (sensory) information?
A. Object Perception: Personalities of a Blob?
context influenced the interpretation of a blob
B. Speech Perception: Speech Segmentation
language enabled speech segmentation
C. Perception of Pain: Placebo effect
expectations of relief caused placebo effect
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How Perception Works: Theories of Object Perception
Learning objectives: By the end of this presentation you will be able to…
recognize that proposed processes of object perception offer complementary explanations of how we make sense of sometimes ambiguous sensory information using heuristics.
describe how, according to Helmholtz, applying the likelihood principle enables unconscious inferences that resolve stimulus ambiguity.
identify several Gestalt rules of form that resolve stimulus ambiguity.
explain how experience with regularities in the environment may provide the basis of our perceptual assumptions; give examples of physical and semantic regularities.
How Perception Works: Processes of Object Perception
I. Overview
Accurately perceiving objects requires that we make sense of sometimes ambiguous sensory information; recall inverse projection problem…
inverse projection problem -problem (faced by the mind) of working backwards from the retinal image to determine the shape of the originating object.
How Perception Works: Processes of Object Perception
I. Overview
Accurately perceiving objects requires that we make sense of sometimes ambiguous sensory information; recall inverse projection problem…
The way that cognitive processes resolve ambiguities is by using satisficing heuristics.
Three processes of object perception, which operate as heuristics are covered, unconscious inference, rules of form, and environmental regularities; they are to be viewed as complementary rather than as alternatives…
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
According to Helmholtz’s theory of unconscious inference…
perception is the result of unconscious inferences (assumptions) we make about the environment.
likelihood principle: we perceive the world in the way that is “most likely” based on our past experiences
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization
proximity
proximity- objects that are close to each other are perceived as a group.
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization (Grouping)
proximity
similarity
similarity- objects that are similar to each other are perceived as a group.
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization (Grouping)
proximity
similarity
good continuation
good continuation- objects that form a continuous straight or curved line are perceived as a group.
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization (Grouping)
proximity
similarity
good continuation
pragnanz
pragnanz- objects that form a pattern that is regular, simple, and orderly are perceived as a group (meta-principle)
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization (Grouping)
proximity, similarity, good continuation, pragnanz
Above principles operate as heuristics
Where Do They Come From?
originally conceived as “intrinsic rules”
modern cognitive psychologists believe they are learned from experience…
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization
C. Experience with Environmental Regularities
physical regularities- regularly occurring physical properties (horizontals and verticals, not obliques)
Some Physical Regularities & Their Effects
horizontals and verticals and the oblique effect-poorer discrimination among oblique objects than among horizontal and vertical ones; due to fewer oblique feature detectors.
Some Physical Regularities & Their Effects
horizontals and verticals and the oblique effect
light from above and the light from above assumption
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization
C. Experience with Environmental Regularities
physical regularities
semantic regularities- characteristics regularly associated with a given scene.
Semantic Regularities
Which Object Does Not Belong In The Scene?
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
A. Unconscious Inference
B. Gestalt Principles of Perceptual Organization
C. Experience with Environmental Regularities
physical regularities
semantic regularities
Environmental regularities are the basis of the assumptions & organizing principles (heuristics) that guide perceptions.
How Perception Works: Processes of Object Perception
I. Overview
II. Processes of Object Perception (look for heuristics)
III. Recap: How do the three processes of object perception illustrate the use of heuristics to resolve the problem of an ambiguous environment?
unconsciously inferring the most likely cause is a heuristic process
Gestalt principles are heuristic rules
environmental regularities provide the basis of assumptions, which are used heuristically.
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Experience-Dependent Plasticity
Learning objectives: By the end of this presentation you will be able to…
define experience-dependent plasticity and describe how it illustrates the influence of experience on bottom-up processing.
describe classic studies of experience-dependent plasticity
Experience-Dependent Plasticity
I. Overview
last time we discussed processes of object perception and learned that experience plays a role in top-down processing (likelihood from experience, rules of form from environmental regularities)
Today we will briefly consider two studies, which show that experience influences bottom-up processing of sensory information.
studies concern experience-dependent plasticity- a change in brain structure as the result of experience
Experience-Dependent Plasticity
I. Overview
II. The Research
A. Blakemoore & Cooper (1970) “kittens in tubes”
To summarize…
reared 3wk-3month old kittens in environments with either horizontal or vertical lines.
kittens failed to respond to stimuli that did not match their rearing environment.
visual cortex of kittens lacked feature detectors tuned to stimuli that did not match their rearing environment.
exposure to normal visual environment within the sensitive period restored vision.
Experience-Dependent Plasticity
I. Overview
II. The Research
A. Blakemoore & Cooper (1970) kittens in tubes study
B. Gauthier et al.’s (1999) Greebles study
measured activity of neurons in FFA, known to respond to faces.
created experts by exgtensively training participants in “Greeble recognition” over a 4-day period…
measured activity of FFA cells again…
that training increased responding to greebles to the same level at which they respond to faces suggests experience plays a role in tuning cells in FFA.
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