1 Perceptual Processes Introduction –Pattern Recognition –Top-down Processing & Pattern Recognition –Face Perception Attention –Divided attention –Selective attention –Theories of attention

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

3 Pattern Recognition The identification of a complex arrangement of sensory stimuli

4 Patterns

5 Glory may be fleeting…

6 The Letter Z

7 Theories of Patter Recognition Template Matching Theory Prototype Models Distinctive Features Model Recognition by Components Model

8 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

9 Examples of Template Matching Attempts

10 Used in machine recognition

11 Problems for Template Matching Inefficient - large # of stored patterns required Extremely inflexible Works only for isolated letters and simple objects

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

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

14 Forming Prototypes of Faces

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

16 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

17 Distinctive Features Models: Evidence Consistent with physiological research Psychological Evidence –Gibson 1969 –Neisser 1964 –Waltz 1975 –Pritchard 1961

18 Visual Cortex Cell Response

19 Gibson--Distinctive Features

20 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?

21 T Z A How a Distinctive Features Model Might Work:

22 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?

23 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

24 Examples of Geons

25 Status of Recognition by Components Theory Distinctive features theory for 3-D object recognition Some research consistent with the model; some not

26 Support for Biederman

27 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

28 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

29 Ambiguous Stimulus -The Man Ran

30 Ambiguous Stimulus - The Cat in the Hat

31 Fido is Drunk

32 Reversible Figure and Ground

33 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.

34 Word Superiority- Non-word Trial

35 Word Superiority: Word Trial

36 Single Letter ‘K’ vs ‘K’ in a word

37 Word Superiority: Single Letter Trial

38 Word Superiority: Word Trial

39 Altered Sentences in Warren and Warren (1970) Sentence that was presentedWord 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

40 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

41 The Influence of Stimulus Features & Sentence Context on Word Identification

42 Attention

43 Definitions of Attention Concentration of mental resources Allocation of mental resources

44 Divided Attention

45 Reinitz & Colleagues (1974) Divided Attention Condition Full Attention Condition Subjects count the dotsNo instruction about dots

46 Proportion of Responses that were “old” for Each of Two Study Conditions and Two Test Conditions (Reinitz & Colleagues, 1994). Study Condition Test Condition Full AttentionDivided Attention Old Face Conjunction Faces.48.42

47 Divided Attention & Practice Hirst, et. al Spelke, 1976

48 Selective Attention

49 Selective Attention (Dichotic Listening Task) Shadowing Irrelevant Channel Cocktail Party Effect - Morray (1959) Wood and Cowan (1995) Treisman (1960)

50 Dichotic Listening Task T, 5, H LEFT T 5 H RIGHT S 3 G

51 Cocktail Effect -- Ziggy

52 Treisman’s Shadowing Study

53 Filter Models of Attention

54 Cerebral Cortex & Attention

55 Capacity Model of Attention

56 Diagnostic Criteria for Automatic Processes

57 Darwin, Turvey, & Crowder