PERCEPTION AND PATTERN
RECOGNITION
• Making sense of sensation
– Local vs. Global scope
– Data-driven (sensory, bottom-up) vs.
Concept-driven (knowledge, “top-down”)
• Organizing the perceptual world
– Gestalt “strategies” of grouping
• Recognizing familiar patterns
– Changes in performance and process as
we practice
• Impairments of pattern recognition
skill
GESTALT “STRATEGIES” OF
PATTERN ORGANIZATION
PROXIMITY
SIMILARITY
CONTINUITY
CLOSURE
ASYMMETRIES IN
HEMISPHERIC PROCESSING
One hypothesis:
Left Hemisphere specialized for
“local detail,” fine-grained analysis
Right Hemisphere specialized for
“global form” and wide scope
Damaged LH
Damaged RH
SOME BASIC FACTS ABOUT
HUMAN PATTERN RECOGNITION
• vast number of distinct patterns can
be learned
– e.g., over 60,000 spoken or written
words
• recognition can with practice by
very fast and “automatic”
– e.g., Lexical Decision Speed
BLACK
BLARK
?
~600 msec
• can succeed in spite of great
variability of input (“noise”)
PRACTICE AND PATTERN
RECOGNITION SKILL
• speed and accuracy improve
• requires less attention and effort
• becomes more “noise resistant”
• “distinctive” features are learned
• “prototype” patterns may be learned
• larger “units of recognition” emerge
• skill, and impairment, are “domainspecific”
THE POWER LAW OF PRACTICE
Speed and accuracy improve,
but at an ever-slower rate
( L O Gm ) i n / p a g e
Task: reading inverted text (Kolers, 1975)
19
16
13
10
7
4
1
2
4
8
16
32
64 128
# of pages read (LOG)
m in / p a g e
100
10
1
2
4
8
16
32
64 128
# of pages read (LOG)
Time = 10
a
x
practice
-b
LEARNING DISTINCTIVE
FEATURES OF PATTERNS
Feature Analysis: Define a small set
of features whose presence and
arrangement defines the patterns
e. g.: consonant phonemes
FEATURES
Voicing
Place of
Articulation
Voiced
Unvoiced
Bilabial
/b/
/p/
Alveolar
/d/
/t/
FEATURES and RELATIONS
Recognizing Objects
by Components
(Biederman’s RBC model)
Fig. 3-17, p. 69
ABSTRACTING THE ”TYPICAL”
PATTERN (PROTOTYPE)
Task: learn to categorize faces: (Reed, ‘72)
Category 1
Category 2
Then tested on old and new faces:
P2
P1
EVIDENCE FOR PROTOTYPE
ABSTRACTION (Reed, 1972)
• “Studied” prototypes are classified
more quickly and accurately than
other studied patterns
• Even if prototype had not been
studied,
– it was still the easiest to classify
– and was often falsely identified as
“studied” in an old/new decision
Reed
Biederman
CARICATURES:
Exaggerating distinctive features
Celebrity caricatures at
About Faces
PRINTED WORDS AS UNITS OF
PATTERN RECOGNITION
Task: letter detection
Reicher (1969): where unitizing helps
30 MSEC WARM
OR WBPM
OR ###M
M
#$%&
N
Then…
(1 sec)
70%C
58%C
62%C
Johnson (1987): where unitizing hurts
“is first letter an “R”?
BEAN faster than BEAR
but BFXN equal to
BFXR
STIMULUS FEATURES AND
SENTENCE CONTEXT
(Rueckl & Oden, 1986)
Task: read sentence contexts,
The { lion tamer / dairy farmer } raised
____ to supplement his income.
s e e in g { b e a r }
then. .
beans
.......
bears
100
80
Dairy Farmer
60
Lion Tamer
40
%
20
0
Stimulus feature (in bea_s)
IMPAIRMENTS OF PATTERN
RECOGNITION SKILL
• Skills, and impairments, tend to be
“domain-specific” to codes or
modality:
– ALEXIA WITHOUT AGRAPHIA
• can’t read, but can write
– PROSOPAGNOSIA
• can’t recognize familiar faces
–MOTION AND COLOR AGNOSIA
•objects appear still, or “grey”
–AMUSIA
•can’t recognize/match familiar melodies
DEVELOPMENTAL DYSLEXIA
• defined as a selective slowness in
reading acquisition and speed
• estimates range from 2% to 10% of
school population
• similar numbers of boys and girls
• not a problem of visual perception
•
perceiving and representing rapid
sequences of speech sounds
• predicted by “phonological
awareness” tests
• reading and complex phonology
remain problems into adulthood