Chapter 3. Perceiving Objects and Recognizing Patterns

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Published on 16 Feb 2011
Central problem of perception is explaining how we attach meaning to the sensory information we receive.
Subdivided into visual, auditory, olfactory, gustatory, and haptic perception categories.
Distal stimulus: an object, event, or pattern as it exists in the world.
Proximalstimulus: reception of information and the registration by a sense organ -for example, retinal images in
the case of vision.
Retinal image: a proximal stimulus for vision, consisting of the projection of light waves reflected from
stimuli and projected to a surface at the back of the eye.
Retina: a layer of visual receptor cells at the rear of the eyeball.
Percept: the outcome of a perceptual process; the meaningful interpretation of incoming information.
Pattern recognition: the classification of a stimulus into a category.
Perception: the interpretation of sensory information to yield a meaningful description or understanding.
One of the most important aspects of visual perception has to do with how we interpret stimulus arrays as consisting of
objects and backgrounds.
Form perception: the process by which the brain differentiates objects from their backgrounds.
Subjectivecontours: illusory outline created by certain visual cues that lead to erroneous form perception. The existence
of this phenomenon suggests that perception is an active constructive process.
Principle of proximity-we group together things that are nearer to each other.
Principle of similarity-we group together elements that are similar to each other.
Principle of good continuity-we group together objects whose contours form a continuous straight line or curved
Principle of closure -we tend to mentally fill the gap to see a closed complete whole figure.
Principle of commonfate-we group together things that move together.
Gestalt principles of perceptual organization: laws that explain the regularities in the way people come to perceptual
interpretations of stimuli. The emphasis is on the apprehension of the whole structures rather than on the detection and
assembly of parts of structures.
This is being formalized with a new theory called minimal model theory.
Law of Pragnanzstates that of all the possible ways of interpreting a display, we tend to select the organization that
yields the simplest and most stable shape or form.
Relatively uninfluenced by expectations or previous learning (the so-called higher-level processes).
Involve automatic, reflexive processing that occurs even when the perceiver is passively regarding the
We will need to have stored an impossibly large number of templates.
Technological advances force us to explain how and when templates are created and how we keep
track of an ever growing number of them.
How do people recognize many patterns as more or less the same thing even when they don't look
the same each time?
Three problems:
Templates: a stored pattern or model to which incoming information is matched in order to be recognized and
Featuralanalysis is the recognition of a whole object depending on recognition of its features.
People use features to recognize letters.
Visual search task: a task in which subjects are asked to detect the presence of a particular target against
an array of similar stimuli.
Pandemoniummodel: a model of letter perception based on a bottom-up hierarchy of feature detectors.
Features: a component, or part, of an object, event, or representation.
Prototype: an abstract representation of an idealized member of a class of objects or events.
An object is "perceived" when a match is found.
When a sensory device registers a new stimulus, the device compares it with previously stored prototypes,
an exact match is not required.
Prototype matching explain perception in terms of matching an input to a stored representation of information,
as do template models.
Bottom-up process: cognitive (usually perceptual) process guided by environmental input. Also called "data-driven"
Two of the biggest problems are:
Top-down process: cognitive (usually perceptual) process directed by expectations (derived from context, past learning,
or both) to form a larger percept, concept, or interpretation. Also called conceptually driven or theory-driven process.
Chapter 3. Perceiving Objects and Recognizing Patterns
Saturday, January 29, 2011
3:39 PM
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