VISUAL PERCEPTION Flashcards
stimuli through
sensory organs
sensation
brain processing and
interpreting stimuli.
typically relate to
identity & form,
pattern & movement
perception
brain determining
future goal
cognition
DISTAL OBJECT
- INFORMATIONAL MEDIUM
- PROXIMAL STIMULATION
- PERCEPTUAL OBJECT
james gibson 1966-1979
object in the external
world
distal object
carries info to the person
informational medium
sensory organ receives
info
proximal stimulation
mental image
perceptual image
mental representation of the stimuli received
percept
we can never
experience the exact
same set of stimuli as
we experienced it
before
stimuli may exist but
without anyone to
sense it, it will not
stabilized images
receptor cells adapt to constant
stimulation by not firing until change in
stimulation
presence of stimulus is not detected
senosry adaptation
gray field replacing stimulus
after senses adapt
ganzfeld effect
em light is transduced &
converted to neural
electrochemical impulses
retina
image is rotated
and falls here
fovea
color
cones
light and dark
rods
light energy to
electrochemical
energy
photoreceptors
- ascends to parietal lobe
Dorsal Pathway (Where)
- descends to temporal lobe
Ventral Pathway (What)
what object is & where it
is
WHAT-WHERE
HYPOTHESIS
what object is & how it
functions
spatial information, how
we situate ourselves
with the object
WHAT-HOW
HYPOTHESIS
- eyes-to-brain perception
- data-driven (stimulus-driven)
BOTTOM-UP THEORIES
- driven by high-level cognitive process, existing
knowledge, & prior expectation
TOP-DOWN THEORIES
- sensory info is all we need to perceive
- “ecological perception”
- sufficient contextual info exists to make perceptual
judgement uwu
Texture Gradients - depth & distance - relative proximity/distance & object parts
+ 30-100ms after visual stimulus, mirror neurons start firing +
GIBSON’S THEORY (1979)
- mind stores templates & patterns that we recognize
- obtaining chunks of knowledge to long-term storage can later be accessed for fast recognition
+ letters & letters are different. left fusiform- letters +
CHUNK-BASED THEORY
FOUR TYPES OF DEMONS:
● Image Demons
● Feature Demons
● Cognitive Demons
● Decision Demons
We attempt to match features of a pattern to features stored in memory, rather than to match a whole pattern to a template or prototype
FEATURE-MATCHING THEORY
● Oliver Selfridge
● Metaphorical “demons”
with specific duties
receive and analyze the
features of a stimulus
THE PANDEMONIUM
THEORY
feature that
give a form its overall shape
Global Feature:
when the letters are close
together at the local level,
people have problems
identifying the local stimuli
(small letters) if they are not
concordant with the global
stimulus (big letter).
Global Precedence Effect:
constitute the
small-scale or detailed aspects
of a given pattern
Local Feature:
when the letters on the local
level are relatively far apart
from each other, it is harder for
people to identify the global
stimulus (big letter) if it is not
concordant with the local
stimuli (small letters)
Local Precedence Effect:
Research showed that the visual cortex contains specific neurons that respond only to a particular kind of stimulus, and only if that stimulus fell onto a specific region of the retina.
Cells seem to show hierarchical structure; At the lowest level, cells respond to lines; at a higher level, they respond to corners and edges, then to shapes, and so forth.
As evidence of this hierarchy, there were once believed to be just two kinds of visual cortex neurons, simple cells and complex cells
NEUROSCIENCE AND
FEATURE-MATCHING THEORIES
we quickly recognize objects by observing the edges of them and then decomposing the objects into geons
Recognition-by-components (RBC) Theory:
According to Irving Bierderman, we recognize 3-D objects by manipulating geometric shapes called
geons.
Studies have found neurons in the inferior temporal cortex that are sensitive to just those viewpoint-invariant properties.
Many neurons, however, respond primarily to one view of an object and decrease their response gradually the more the object is rotated.
This finding contradicts the notion of Biederman’s theory that we recognize objects by means of viewpoint-invariant geons. As a result, it is not clear at this point whether Biederman’s theory is correct.
NEUROSCIENCE AND
RBC THEORY
Also known as Intelligent Perception
The perceiver builds (constructs) a cognitive understanding (perception) of a stimulus
The concepts of the perceiver and his or her cognitive processes influence what he or she sees. The perceiver uses sensory information
as the foundation for the structure but also uses other sources of information to build the perception
Higher-order thinking plays an important role in perception; also
emphasizes the role of learning in perception
CONSTRUCTIVE PERCEPTION
The percepts are based on the following:
● What we sense (the sensory data)
● What we know (knowledge stored in memory)
● What we can infer (using high-level cognitive processes)
The process by which we
unconsciously assimilate
information from a number of
sources to create a perception
Unconscious Inference
Objects presented in certain
configurations are easier to
recognize than the objects presented
in isolation, even if the objects in the
configurations are more complex
than those in isolation
Configural-superiority effect
A target line that forms a part of
a drawing of a 3-D object is
identified more accurately than a
target that forms a part of a
disconnected 2-D pattern
Object-superiority effect
indicates that when people are
presented with strings of letters,
it is easier for them to identify a
single letter if the string makes
sense and forms a word instead
of being just a nonsense sequel
of letters.
Word-superiority effect
Individual stores the way the object looks
to him or her
Viewer-centered perception
Individual stores a
representation of the object
Object-centered perception
Information is characterized by its
relation to a well-known or prominent
item
Landmark-centered perception
● Useful for understanding how we perceive groups of objects or even
parts of objects to form integral wholes
● Kurt Koffka, Wolfgang Kohler, and Max Wertheimer
GESTALT LAWS
We tend to perceive any
given visual array in a way
that most simply
organizes the different
elements into a stable and
coherent form
LAW OF PRAGNANZ
Other Gestalt principles:
● Figure-ground
perception
● Proximity
● Similarity
● Continuity
● Closure
● Symmetry
Specializes in recognizing parts of objects and in assembling those parts into distinctive wholes
Feature Analysis System
Specializes in recognizing larger configurations, not analyzing
parts of objects or the construction of the objects
Configurational System
The fusiform gyrus is activated when one examines items with which one has visual expertise.
Expert-individuation hypothesis:
inability to recognize faces
Prosopagnosia:
- Occurs when our
perception of an
object remains the
same even when
our proximal
sensation of the
distal object
changes
(Gillam, 2000)
perceptual constancy
- The perception that an object maintains the
same size despite changes in the size of the
proximal stimulus.
SIZE CONSTANCY
- The perception that an object maintains
the same shape despite changes in the
shape of proximal stimulus.
SHAPE CONSTANCY
Depth is the distance from a surface, usually using your own body as a reference surface when speaking in terms of depth perception.
DEPTH PERCEPTION
- It can be represented in just two dimensions and observed with just one eye.
Monocular depth cues
- It is based on the receipt of sensory information in three dimensions from both
eyes.
Binocular depth cues
Your two eyes send increasingly disparate (differing) images to your brain as objects approach you.
Binocular disparity
Your two eyes send increasingly turn inward as objects approach you.
Binocular convergence
- Trouble perceiving sensory information. It is often are caused by damage to the
border of the temporal and occipital lobes. - People who suffer from visual-object agnosia can see all parts of the visual field,
but the objects they see do not mean anything to them.
Agnosia
An individual is unable to pay attention to more than one object at a time.
SIMULTAGNOSIA
Severely impared ability to recognize human faces.
PROSOPAGNOSIA
- An impaired ability to use the visual system to
guide movement. - Ataxia results from a processing failure in the
posterior parietal cortex, where sensorimotor
information is processed. - People with this deficit have trouble reaching for
things.
Optic Ataxia
Color perception deficits
are much more common in
men than in women, and
they are genetically linked.
ANOMALIES
IN COLOR
PERCEPTION
- Least common, people with this condition have no color vision at all.
- In this condition the cones are nonfunctional.
Rod monochromacy / achromacy
- Only two of the mechanisms for color perception work, and one is
malfunctioning. - People with this form of color-blindness have difficulty in
distinguishing red from green although they may be able to
distinguish, for example, dark red from light green.
Dichromacy
- The extreme form of red-green color blindness
Protanopia
- Trouble seeing greens with symptoms similar to protanopia.
Deuteranopia
- Confusions of blues and greens, and yellows that disappear or
appear as light shades of reds
Tritanopia
