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Psychology of visual perception
COMMUNICATION DESIGN,
ANIMATED IMAGE
2014/2015
Lesson #5: Oct. 20th 2014
Lecture plan:
PERCEPTUAL CONSTANCY
GENERAL ASPECTS
SHAPE CONSTANCY;
SIZE CONSTANCY;
COLOUR CONSTANCY;
NATURE AND FUNCTION OF PERCEPTUAL CONSTANCY
Extended lesson summary:
PERCEPTUAL CONSTANCY
GENERAL ASPECTS
DEFINITION:

Perceptual constancy, also called Object Constancy, or Constancy Phenomenon,
refers to the tendency to see familiar objects as having standard shape, size,
colour, or location regardless of changes in the angle of perspective, distance, or
lighting. The impression tends to conform to the object as it is or is assumed to
be (distal stimulus), rather than to the actual stimulus (proximal stimulus).
Perceptual constancy is responsible for the ability to identify objects under
various conditions, which seem to be “taken into account” during a process of
mental reconstitution of the known image. For example, snow appears white in
the low illumination of moonlight, as well as in sunlight 800,000 times as bright.
Perceptual constancy is reduced by limited experience with the object and by
decreasing the number of environmental cues that aid in identification of the
object.
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Our knowledge of the world is not elementary. It is categorical (we do not see
concrete singular objects, we see categories:- a car, a chair, a tree, etc.).
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PSYCHOLOGY OF VISUAL PERCEPTION
2014/2015
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Process with 2 steps:
o Forming of categories – from permanent, specific and essential
characteristics of objects;
o Inclusion in a category.
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Problem of perceptual constancy:
o Categories = stable and simple characteristics;
o Vision depends on fluid and complex elements;
o There is no direct correspondence between physical image (proximal
stimulus) and the psychological image.
SHAPE CONSTANCY
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The percept of the shape of objects:
o remains constant despite changes in the image that is projected on the
retina;
o follows the characteristics of the distal stimulus-not the proximal
stimulus.
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If we were asked the shape of the door in the three images above we would say: rectangular, even though we only see really a rectangle on the first image.
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PSYCHOLOGY OF VISUAL PERCEPTION
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2014/2015
Shape constancy is related to object recognition. If we see a coin in the first row
above we see it having a round shape in the four instances.
In the row bellow, as we cannot recognize any familiar object, we would naturally
see an oval shape.
Explanatory theories:
o Gestalt theory (top/base):
 the constancy of the form involves a relationship between
perceived shape and orientation of the object;
 the processes of categorization and conceptualization are top-base
processes.
o Gibson Ecological theory (base/top):
 the constancy of shape is based on purely optical data (optical
flows, gradients of texture and projection invariants);
SIZE CONSTANCY
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Two Facts:
o Retinal image size varies inversely with the distance;
o The perceived size of an object is the same, be it near or away;
Two factors:
o Perceived distance;
o Familiarity with the subject.
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PSYCHOLOGY OF VISUAL PERCEPTION
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2014/2015
In the images above the perspective lines provide depth cues that makes our
visual system perceive the figures that are higher in the visual field as being at a
greater distance from the observer that the figures that are lower in the visual
field. So, if at a greater distance, the retinal stimulus is the same, so the figures
should be bigger.
COLOUR CONSTANCY
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The color of the objects tends to remain constant regardless of the luminosity
level that hit the objects surface.
BRIGHTNESS CONSTANCY
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The brightness of an object remains constant despite variations in the level of the
amount of light that falls on it;
An bright object dimly lit (less luminosity) will seem allways more clear than a
dark object well lit (more light over it);
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PSYCHOLOGY OF VISUAL PERCEPTION
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The constancy of clarity is due to the albedo of surfaces in our environment.
Albedo (al-bee-doh) is a measure of how much light that hits a surface is reflected
without being absorbed. Something that appears white reflects most of the light
that hits it and has a high albedo, while something that looks dark absorbs most
of the light that hits it, indicating a low albedo.
NATURE AND FUNCTION OF PERCEPTUAL CONSTANCY
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Perceptual constancy:
o Keeps us in touch with the real things in a perfectly solid and stable way;
o It's not a unique process – several aspects involving different cues;

Stability and perceptual consistency is obtained from categorization and
conceptualization processes.

Functions-of perceptual constancy:
o simplify our perception, making the complexity manageable;
o accelerate recognition of shapes, sizes and colors;
o reduce the effort of learning;
o allow the optimization of past experience;
o allow inferences about subsequent attributes;
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PSYCHOLOGY OF VISUAL PERCEPTION
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2014/2015
make events predictable;
support the systematization and the regularity of processes;
facilitate the linkage and coordination of social behaviors because they
provide shareable conceptual frameworks;
adapt the world to our needs and objectives;
make the world seem more significant.
Faro, 16/10/2014
Professor in charge of CU:
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