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 LHDamaged RH

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 ? ~600 msec BLARK can succeed in spite of great variability of input (“noise”) SOME BASIC FACTS ABOUT HUMAN PATTERN RECOGNITION

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 “domain- specific”

THE POWER LAW OF PRACTICE Speed and accuracy improve, but at an ever-slower rate Task: reading inverted text (Kolers, 1975) Time = 10 x practice a-b

LEARNING DISTINCTIVE FEATURES OF PATTERNS Feature Analysis: Define a small set of features whose presence and arrangement defines the patterns FEATURES Voicing Place of Articulation VoicedUnvoiced Bilabial Alveolar /b/ /p/ /d//t/ e. g.: consonant phonemes

Fig. 3-17, p. 69 FEATURES and RELATIONS Recognizing Objects by Components (Biederman’s RBC model)

ABSTRACTING THE ”TYPICAL” PATTERN (PROTOTYPE) Task: learn to categorize faces: (Reed, ‘72) Category 1 Category 2 Then tested on old and new faces: P2P1

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 ReedBiederman

CARICATURES: Exaggerating distinctive features Celebrity caricatures at About Faces

PRINTED WORDS AS UNITS OF PATTERN RECOGNITION Task: letter detection WARMWBPM###M OR 30 MSEC Then… (1 sec) M #$%& N Reicher (1969): where unitizing helps 70%C58%C62%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. then.. bears beans

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