Perceptual Strategy: a tale of letters and shapes Cees van Leeuwen Laboratory for Perceptual...
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Transcript of Perceptual Strategy: a tale of letters and shapes Cees van Leeuwen Laboratory for Perceptual...
Perceptual Strategy: a tale of letters and shapes
Cees van LeeuwenLaboratory for Perceptual Dynamics, KU Leuven
[email protected] collaboration withThomas Lachmann
Kaiserslautern University of Technology
Overview
• Introduction: two ways in which knowledge influences perception
• Reading deficits as a consequence of learning the wrong strategy
• Differentiation in strategies between nonletters and letters
• Conclusions
Two ways in which knowledge influences perception
1. What we know influences what we perceive
The figure is determined based on familiarity. Peterson & Gibson (1993).
2. Knowledge influences how we perceive
Perceiving items as shapes vs perceiving items as letters
Habitual, as a result of learning to read!
Are Letters Special?
They are perfectly natural!
If letters are normal, why do some children have difficulty in learning to read and write?
Developmental Dyslexia
Reading Errors- Slowness of reading; problems in
understanding written materials- Losing their Line- Omissions, Repetitions, Substitution,
Insertions- Distortions of Words, Parts of Words- Reversal Errors: was ∞ saw b ∞ d
ORTON (1925) Cardinal symptom
The Causes are unknown
After more than 100 years of experimental studies
-------------------------------------------------------------------------------------------------------------Acoustic information processing VERSUS phonological deficitversus versusVisual information processing orthographical deficit
But perhaps it is both, or a more general deficit.
Thomas Lachmann’s Functional Coordination Deficit model
Not a deficit of automatization, but automatization of the wrong strategy
Our participants
57 third/fourth graders School psychologists‘ diagnosis in Grade 2Own diagnosis prior to experiment: Discrepancy Definition (2 SD Reading time SLRT vs. Raven)
The Cardinal Symptom
b vs. d vs. p vs. q
Problem with visuospatial processing of symbols?
Mental Rotation
Cooper & Shepard (1973)
Rusiak, Lachmann, Jaskowski, van Leeuwen (Perception, 2007)
N = 16 DyslexicsN = 12 Controls
R, F, G, e, k (0-180° in 45°)
“normal” oder “mirror images”?
Mental Rotation with Letters
Pressmirrored
500
700
900
1100
1300
0 45 90 135 180
Angle of Rotation
RT
(m
s)Dyslexics
Controls
Mental Rotation with Letters
- Typical Mental Rotation Effect
- Group effect (> 100 ms)
- No Interaction (no visuospatial processing deficit)
The Cardinal Symptom
b vs. d vs. p vs. q
If the problem is not with visuospatial processing, perhaps it has something to do with the structure of the configuration
SYMMETRY
Symmetry
• Makes your world simpler
• Simple patterns have few alternatives
Rotation and Reflection Symmetry Groups
Equivalence Sets (ES)Equivalence Sets Size (ESS)
Garner Patterns
Task
• Serial presentation of pairs of stimuli
ISI = 500 ms• Same or
different• Irrespective of
pattern orientation
General preference for Symmetry
Detailed model predictions possible from Degree of Pattern Symmetry (ESS) and Degree of “Sameness” (IM, CM, or NM)
Lachmann & van Leeuwen (2004) Scientific Psychology Series
Model Fit
Lachmann & van Leeuwen, 2005, Quarterly Journal of Experimental Psychology
Normals vs Dyslexics
Letters vs Shapes
Lachmann & van Leeuwen, 2007, Developm. Neuropsychology
Results
PatternsLetters
RT
(m
s)
1100
1000
900
800
700
600
symmetric
asymmetricPatternsLetters
RT
(m
s)
1100
1000
900
800
700
600
symmetric
asymmetric
Material**; Symmetry**; Group*; Material x Symmetry x Group **
Normal reading children Dyslexics
No effects on error rate No effects on error rate
Model fit*
Predicted RT (ms)
11001000900800700600
RT
(m
s)
1200
1100
1000
900
800
700
600
Dyslexics
Normal
Readers
*Note on Model fit
• Model fit was based on different assumptions for Normals and Dyslexics
• Degree of symmetry for patterns was counted for both Normals and Dyslexics
• Degree of symmetry for letters was counted for Dyslexics but ignored for Normals
• Dyslexics are faster because they give equal importance to Symmetry in Letters and Shapes
------------
Dyslexics:
• Outperform normal readers on this task• The task involves letters
• Why don’t dyslexics read better than normals?
Symmetry?
• Symmetry helps in perceiving shapes, but hinders in perceiving letters
• Strategy, based on reading practice
• When learning to read is difficult anomalous strategies
letter symmetry may be suppressed actively
Configurations
Emergent Properties (J.R. Pomerantz)
( ( (( ()
Configurations
Difficulty of recognizing the letter “E” when embedded in a Good
figure
Configurations
Some Congruence Effects
GREEN
RED
Push the button on the
Right
Letters
versus
Shapes
Letters vs Shapes
Congruent versus Incongruent
Van Leeuwen & Lachmann, Perception & Psychophysics, 2004
435
440
445
450
455
460
465
470
475
480
Letters Shapes
CongruentIncongruent
Binary Classification
Van Leeuwen & Lachmann, Perception & Psychophysics, 2004
410
420
430
440
450
460
470
480
490
Letters Rotated Letters Pseudo-Letters
CongruentIncongruent
Binary Classification
Binary Classification
• Rotated letters Pseudo-letters, and Geometrical Shapes show Congruence Effects.
• Letters show Negative Congruence Effects.
• Is the effect related to the response alternatives?
Contrasting Response Categories
Similarity
Press Left Button: C or Circle or L or Rectangle
Press Right Button: H or Square or A or Triangle
No Similarity
Press Left Button: C or Square or L or Triangle
Press Right Button: H or Circle or A or Rectangle
Similarity
0
100
200
300
400
500
600
Letters Shapes
CongruentIncongruent
455
460
465
470
475
480
485
490
495
Letters Shapes
CongruentIncongruent
Contrasting Response Categories
No Similarity
• What about less experienced readers?• What about developmental dyslexics?
In normal adult readers:
Dissociation in Early Visual IntegrationProcesses of Letters and Shapes
Binary Classification
Normal ReadingChildren
537541 553531 546547N =
MATERIAL
shapeletter
95
% C
I R
T
560
540
520
500
480
460
CONINCON
iso
con
incon
648642 651620 669638N =
MATERIAL
shapeletter
95
% C
I R
T
600
590
580
570
560
550
540
530
520
CONINCON
iso
con
incon
• Weaker dissociation in normal children than in adults
• Dyslexics have increased response times and variance AND an adult dissociation pattern
PUZZLE
DyslexicChildren
RT (ms)
RT (ms)
Puzzle
Normal reading children have a weaker dissociation than adults strategy differentiation not yet well established?
Dyslexics probably do not have more reading experience dissociation should be same or even weaker
Quod Non!
Puzzle
Our Dyslexics sample has:
-slow response rates
-strong dissociation
Does this mean that all individuals in the sample have both these characteristics?
Puzzle
Perhaps:
-slow response rates Subpopulation I
-strong dissociation Subpopulation II
Subtypes of Dyslexia?
Analogy with Lachmann (2003, 2005)
Puzzle
Diagnostic subgroups
Reading test: SLRT (Landerl, Wimmer, & Moser, 1997) word and non-word reading subtests
Non-Word Reading Impaired (NWRI):at least reading time in non-word reading > 2 SD
Frequent Word Reading Impaired (FWRI):reading time in frequent word reading > 2 SD, but normal non-word reading time (within 1 SD)
Puzzle
FWRI NWRI
Fuchs &Lachmann (2003)
Lachmann (2007)
Lachmann et al.(2005)
Delayed auditory/visualsyllable discrimination
Delayed letter identification
Attenuated mismatchnegativity syllables
Pronounced fast-same effect in visual conditions
Normal mismatch negativity
Large modality effects
increased response times but normal between conditions effects
specific effects enhancedmostly involvingvisuo-auditory coordination
Same-Different Task• Sequential presentation of
two items
• First always isolated, second isolated or in congruent or incongruent surroundings
• Letters, Pseudo-letters, Shapes; No mixed-category pairs
• Adults, normal reading children, FWRI vs NWRI dyslexics
Material x congruence x group.
Group MaterialCongruence
Isolated Congruent Incongruent
Normal reading adults
Letters 478 483 483
Pseudo-letters 501 498 515
Shapes 459 482 519
Normal reading Children
Letters 690 673 722
Pseudo-letters 698 737 771
Shapes 694 724 746
FWRI-dyslexics
Letters 1006 965 1059
Pseudo-letters 990 1015 1085
Shapes 1016 1035 1122
NWRI-dyslexics Letters 745 836 755
Pseudo-letters 792 797 774
Shapes 712 784 842
Summary
• No differences in visuospatial manipulation• Dyslexics sometimes even better than Normals
• Letter/Non-letter Dissociation
• Anomalous in Dyslexics
• Subgroups can be identified:
-- “General Slowing down” in FWRI
-- Enhanced Dissociation in NWRI
Hot from the PressFernandes, T., Vale, A.P., Martins, B., Morais, J., & Kolinsky, R. (2014) Processing in
Developmental Dyslexia: Combining evidence from dyslexics, typical readers and illiterate adults. Developmental Science.
To clarify the link between anomalous letter processing and developmental dyslexia, we examined the impact of surrounding contours on letter vs. pseudo-letter processing by three groups of children – phonological dyslexics and two controls, one matched for chronological age, the other for reading level – and three groups of adults differing by schooling and literacy – unschooled illiterates and ex-illiterates, and schooled literates. For pseudo-letters, all groups showed congruence effects (CE: better performance for targets surrounded by a congruent than by an incongruent shape). In contrast, for letters, only dyslexics exhibited a CE, strongly related to their phonological recoding abilities even after partialling out working memory, whereas the reverse held true for the pseudo-letter CE. In illiterate adults, the higher letter knowledge, the smaller their letter CE; their letter processing was immune (to some extent) to inference from surrounding information. The absence of a letter CE in illiterates and the positive CE in dyslexics have their origin in different aspects of the same ability, i.e. phonological recoding.
A straightforward replication but with more straightforward results
Conclusion
Possible mechanisms:
•Letter treated same as non-letter shapes?
•Problems with surrounding noise suppression?
Thanks to:
• Prof. Thomas Lachmann, TU Kaiserslautern
and his students: Jessika Wüst, Katrin Berg, Sabine Jenke, Sandra Schlademann, Patricia Rusiak, Dave Barton e.a.
• Third Primary School Leipzig
…and to you for your patience!