Perceptual Processes

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Perceptual Processes

• Introduction
• Pattern Recognition
• Top-down Processing Pattern Recognition
• Face Perception
• Attention
• Divided attention
• Selective attention
• Theories of attention

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Perception

• Process that uses our previous knowledge to
  gather and interpret the stimuli that our senses
  register

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Pattern Recognition

• The identification of a complex arrangement of
  sensory stimuli

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Patterns
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Glory may be fleeting
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The Letter Z
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Theories of Patter Recognition

• Template Matching Theory
• Prototype Models
• Distinctive Features Model
• Recognition by Components Model

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Template Matching Theory

• Compare a new stimulus (e.g. T or 5) to a set
  of specific patterns stored in memory
• Stored pattern most closely matching stimulus
  identifies it.
• To work must be single match
• Used in machine recognition

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Examples of Template Matching Attempts
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Used in machine recognition
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Problems for Template Matching

• Inefficient - large of stored patterns required
• Extremely inflexible
• Works only for isolated letters and simple objects

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Prototype Theories

• Store abstract, idealized patterns (or
  prototypes) in memory
• Summary - some aspects of stimulus stored but not
  others
• Matches need not be exact

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Forming Prototypes Faces--Faces Animated Version
Examine the faces below, which belong to two
different categories.
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Forming Prototypes of Faces
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Prototypes

• Family resemblances (e.g. birds, faces, etc.)
• Evidence supporting prototypes
• Problems - Vague not a well-specified theory of
  pattern recognition

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Distinctive Features Models

• Comparison of stimulus features to a stored list
  of features
• Distinctive features differentiate one pattern
  from another
• Can discriminate stimuli on the basis of a small
  of characteristics features
• Assumption feature identification possible

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Distinctive Features Models Evidence

• Consistent with physiological research
• Psychological Evidence
• Gibson 1969
• Neisser 1964
• Waltz 1975
• Pritchard 1961

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Visual Cortex Cell Response
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Gibson--Distinctive Features
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Letter Scanning Example
First, scan for the letter Z in the first
column of letter strings. Next, scan for the
letter Z in the second column of letter
strings. Which is easier? Why?
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How a Distinctive Features Model Might Work
Z
A
T
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Distinctive Features

• Theory must specify how the features are
  combined/joined
• These models deal most easily with fairly simple
  stimuli -- e.g. letters
• Shapes in nature more complex -- e.g. dog, human,
  car, telephone, etc
• What would the features here be?

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Recognition by Components Model

• Irving Biederman (1987, 1990)
• Given view of object can be represented as
  arrangement of basic 3-D shapes (geons)
• Geons derived features or higher level features
• In general 3 geons usually sufficient to identify
  an object

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Examples of Geons
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Status of Recognition by Components Theory

• Distinctive features theory for 3-D object
  recognition
• Some research consistent with the model some not

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Support for Biederman
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Summary

• Distinctive Features approach currently strongest
  theory
• Perhaps all 3 approaches (distinctive features,
  prototypes, recognition by components) are
  correct
• Regardless, pattern recognition is too rapid and
  efficient to be completely explained by these
  models

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Two types of Processing

• Bottom-up or data-driven processing
• Top-down or conceptually driven processing
• Theme 5 -- most tasks involve bottom-up and
  top-down processing

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Ambiguous Stimulus -The Man Ran
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Ambiguous Stimulus - The Cat in the Hat
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Fido is Drunk
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Reversible Figure and Ground
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Word Superiority Effect

• We can identify a single letter more rapidly and
  more accurately when it appears in a word than
  when it appears in a non-word.

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Word Superiority- Non-word Trial
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Word Superiority Word Trial
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Single Letter K vs K in a word
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Word Superiority Single Letter Trial
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Word Superiority Word Trial
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Altered Sentences in Warren and Warren (1970)
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The Effect of Varying Sentence Frame Context on
Interpreting an Ambiguous Stimulus
botanist

• The __________ raised (________) to supplement
  his income.

lion tamer zoo keeper botanist dairy farmer
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The Influence of Stimulus Features Sentence
Context on Word Identification
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Attention
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Definitions of Attention

• Concentration of mental resources
• Allocation of mental resources

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Divided Attention
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Reinitz Colleagues (1974)
Divided Attention Condition
Full Attention Condition
Subjects count the dots
No instruction about dots
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Proportion of Responses that were old for Each
of Two Study Conditions and Two Test Conditions
(Reinitz Colleagues, 1994).
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Divided Attention Practice

• Hirst, et. al. 1980
• Spelke, 1976

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Selective Attention
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Selective Attention (Dichotic Listening Task)

• Shadowing
• Irrelevant Channel
• Cocktail Party Effect - Morray (1959)
• Wood and Cowan (1995)
• Treisman (1960)

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Dichotic Listening Task
T, 5, H
LEFT T 5 H
RIGHT S 3 G
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Cocktail Effect -- Ziggy
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Treismans Shadowing Study
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Filter Models of Attention
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Cerebral Cortex Attention
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Capacity Model of Attention
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Diagnostic Criteria for Automatic Processes
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Darwin, Turvey, Crowder