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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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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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Examine the faces below, which belong to two different categories.

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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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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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T

ZA

How a Distinctive Features Model Might Work:

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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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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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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)

Sentence that was presented Word Heard

It was found that the *eel was on the axle

It was found that the *eel was on the shoe

It was found that the *eel was on the orange

It was found that the *eel was on the table

wheel

heel

peel

meal

*Denotes the replaced sound

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The Effect of Varying Sentence Frame Context on Interpreting an Ambiguous Stimulus

The __________ raised (________) to supplement his income.

lion tamer

zoo keeper

botanist

dairy farmer

botanist

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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).

Study Condition

TestCondition

Full Attention Divided Attention

Old Face .81 .48

ConjunctionFaces

.48 .42

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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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Treisman’s 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 and Controlled ProcessesAutomatic Controlled

1. The process occurs withoutintention , wit hout a consciousdecision.

2. the mental process is not open toconscious awareness orintrospection.

3. The process consumes few i f anyconscious resources; that is, itconsumes littl e if any consciousattention.

4. (Informal) The process operatesvery rapid ly, usually w ithin onesecond.

1. The process occurs only withintention , wit h a deli beratedecision.

2. The process is open to awarenessand introspection .

3. The process uses consciousresources; that is, it d rains the poolof conscious attentional capacity.

4. (Informal) The process is relativelyslow, taking more than a second ortw o for completion.

Part ial Autonomy/ AutomaticityA process is said to be partially autonomous if it can begin automatically butrequi res a more conscious set of operations for completion (see Zbrodoff &Logan, 1986).

Diagnostic Criteria for Automatic Processes

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Darwin, Turvey, & Crowder