Title: Perception and Pattern Recognition
1Chapter 3
- Perception and Pattern Recognition
2Visual Perception
CHILVR Cornea, aqueus Humor, Iris, Lens,
Vitreous humor, Retina
3Eye Anatomy
- Iris
- Cilliar Muscle
- Aqueous Humor
- Pupil
- Lens
- Cornea
- Retina
- Vitreous Humor
- Fovea
- Blind Spot
- Optic Nerve
- Rod
- Cone
- Ganglion Cell
- Bipolar Cell
- Horizontal Cell
4The Fovea
- Light from direct focus lands in the Fovea.
- Contains almost all cones.
- Acuity -- accurate, precise vision-- is best in
the fovea. - Rods are abundant at the sides (periphery) of the
fovea.
5Sensation versus Perception
- Sensation
- The reception of energy from the environment, and
its initial encoding into the nervous system. - Perception
- The process of interpreting and understanding
sensory information.
6Sensation Perception
7Gathering Visual Information
- Saccades Rapid eye movements.
- Last between 25 and 100 msec.
- Fixations Pauses between saccades.
- The eye takes in visual information during
fixations. - 200msec
8Gathering Visual Information
- Change Blindness The failure to notice changes
in visual stimuli (e.g. photographs) when those
changes occur during a saccade. - Inattentional Blindness We sometimes fail to
see an object we are looking at directly, even a
highly visible one, because our attention is
directed elsewhere.
9Visual Sensory Memory
- Also known as Iconic Memory.
- Visual persistence The apparent persistence of a
visual stimulus beyond its physical duration (To
demonstrate Rapidly wobble a pencil between two
fingers).
10Sensory Memory
- How do you study sensory memory?
- Because it is so brief it is difficult to study
- Sperling (1960) hypothesized that we have a
visual memory - He couldnt prove it because it always faded
before people could report it - What to do?
11Sperlings Experiment (Overview)
- Used a tachistoscope to rapidly present images to
the eyes. - Subjects saw a 3 x 4 grid of letters, presented
very briefly (50 ms). - Subjects were asked to recall all the letters
(Whole Report) - Whole report performance was poor (about 37
accuracy).
12Whole Report
?
A N X B L F S M R P K V
(5-500ms)
(50ms)
13Sperling (1960)
- In the whole report condition, subjects had to
recall all the letters they could - Performance was poor
- 4.5/12 letters
- 37 accuracy
- The span of immediate memory
- The number of individual items recalled after a
short delay
14Sperling (1960)
- But is this correct?
- All the letters might be available initially, but
then fade before they can be reported - If this is correct then subjects should be
accurate reporting on any one row (before too
much fading takes place)
15Sperlings Experiment
- The partial report condition, in which only one
of the rows was to be reported - A tone was used as a cue
- A high pitch tone cued recall of the top row
- A medium pitch tone cued recall of the middle row
- A low pitched tone cued recall of the bottom row
16Sperlings Experiment
- Partial report accuracy was much better
- 0 ms delay 76 accuracy
- So memory for entire display is about 76
- A lot more information is there, than can be
reported - 250ms delay 36 accuracy
- Like the whole report condition
17Sperlings Experiment
18Sperlings Experiment(Continued)
- In the partial report condition, a tone was
sounded right after the letter grid disappeared. - A high pitch tone cued recall of the top row a
medium pitch tone cued recall of the middle row
a low pitched tone cued recall of the bottom row. - Partial report accuracy was at 76.
19Sperlings Experiment(Conclusion)
- Why did Sperling argue that decay rather than
interference is the loss mechanism in iconic
memory? - How long does information remain in iconic
memory?
20Lab Journal - Overview
- Only write up experiments on syllabus
- Single Page per Expt
- Number Pages -- everyones page 23 should have
the same one. - Use graphs when possible (picture 1000 words)
- Turn in at Midterm (for review) and then at Final
Exam for scoring
21(No Transcript)
22One subjects results on the number of letters
available for report
23Erasure and Masking Averbach and Coriell (1961)
- Presented two rows of eight letters each.
- Used a visual cue, above or below the
to-be-recalled letter. - The circle-maker cue masked perception of the
letter. - Backward Masking When a later visual stimulus
affects perception of an earlier one.
24 X R F T L W Z P C A K N D E W J
50 ms
25 X R F T L W Z P C A K N D E W J
50 ms
26Averbach Coriell (1961)
- With the bar cue accuracy was similar to
Sperlings original findings - High performance with short delays
- Lower performance with longer delays
- Effective duration of about 250 ms
27Averbach Coriell (1961)
- With the circle cue performance decreased
dramatically - Accuracy was at chance
- Participants did not even see a letter in that
location, they only saw the circle - The circle erased or masked the memory for that
letter
28Averbach Coriell (1961)
- Backward Masking When a later visual stimulus
affects perception of an earlier one - Incoming information (circle) masked information
that was already in iconic memory (letter) - Implicit priming Information is still being
processed, even though it has not been
transferred into awareness
29Ecological Validity and the Icon
- Haber (1983)
- The iconic memory is irrelevant to real-world
perception. - Data are useful only if reading in a lightning
storm - Criticisms of Haber?
- 1. Text reading task shows that perception
actually is like reading in a lightning storm
-- we only fixate for 50msec - 2. Reductionism
30Pattern Recognition
- How do we assemble visual input into meaningful
shapes? - Recognition of Letters
- Pandemonium
- Recognition of Objects
- Recognition by Components
- Context and Connectionism
- Visual Agnosia
31Models of Pattern Recognition
- The Template approach
- Feature analysis / Feature detection
- Connectionism
- Recognition by components (object recognition)
32Template Matching
- Categorize based on a Template (stored
representation of all patterns) - To perceive meaning, simply match the sensory
input with a stored patten. When a match is
found, you are done.
33Template Matching
34Template Matching Problems
- Only possible in very limited domains (such as
reading numbers 012345679) - How would training work?
- Evidence clearly shows you can recognize (pattern
match) objects youve never seen before. - Conclusion -- probably not how the brain works,
and probably not a great way to program a
computer either.
35Feature Analysis ? Letters
- Categorization by features
- A simple fragment or component that can appear in
combination with other features - Recognize letters by breaking them apart into
features -
- H A T L F
36Feature Analysis ? Letters
- We recognize the features of letters (lines,
curves) not the letters themselves - Pandemonium Model (Selfridge, 1959)
- Decision Demons
- Cognitive Demons
- Computational Demons
- Data Demons
37Pandemonium
38Pandemonium Model(Selfridge, 1959)
- Demons Mental mechanisms that process visual
stimuli ? Shout as they identify patterns - Data Demons Encode a pattern
- Computational (Feature) Demons Feature
analyzers each has a single feature it tries to
match - Cognitive Demons Each represents a letter of
the alphabet wait for the right combination of
features - Decision Demon Has the final say in recognizing
the pattern
39Pandemonium Model
- Each node has only one simple job to do
- Includes parallel-processing
- Neurologically valid
40Context Effects
- Data Driven (bottom-up)
- Processing is driven by the stimulus.
- Conceptually Driven (top-down)
- Processing is driven by higher level knowledge.
41Examples of Top-Down Processing
42Connectionism
- Input Units
- Hidden Units
- Output Units
- Back Propagation
- Delta Rule
- Distributed Representation
- Local Minima
- Massively Parallel Processing
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44Feature Analysis ? Objects
- Recognition by Components (RBC)
(Biederman, 1987, 1990) - All objects are a combination of geons ? Look up
the combination to see which object matches - Geons
- Feature detectors identify the geons based on
45Geons The Objects They Make
46Evidence for RBC
- Data on Non-Recoverable Drawings
- Impaired recognition if not able to identify the
geons - Degraded so no intersections
- Performance at chance
- When the same percentage of information was
deleted but NOT at intersections (recoverable
drawings) performance was at 75 accuracy
47RBC
- Limitations of the model
- Only allows for data-driven processes (parsing
and assembling) - Whole vs. part perception
- Suggests that the whole is perceived by
identifying the parts first ? but people perceive
the overall shape as quickly and accurately as
they perceive the components - Neuropsychological evidence
- Object recognition is a joint effort between two
mental processes ? one for features, one for
global shape
48Recognition by ComponentsBiederman (1987)
- Geons building blocks of visual objects.
- Data on Non-recoverable Drawings.
- Limitations of the model
- Over-reliance on data-driven processes?
- Whole versus part perception?
- Neuropsychological evidence?
49Agnosia
- Failure or deficit in recognizing objects. Not
blindness or poor vision. - Apperceptive Agnosia (patterns)
- Associative Agnosia (meanings)
- Prosopagnosia Associative agnosia for faces
50Example of Copying by a Patient with Apperceptive
Agnosia
51Neuropsychology of Object Recognition
- Associative Agnosia
- Can copy drawings
- Can combine the features into a whole pattern,
but cannot associate the pattern with meaning - Can copy a drawing of an anchor and give an
accurate definition of an anchor - Cannot draw the anchor from memory nor identify
the drawing that he copied - Damage to both hemispheres (temporal lobe)
52Example of Copying by a Patient with Associative
Agnosia
53Neuropsychology of Object Recognition
- Prosopagnosia
- The Man Who Mistook His Wife for a Hat Ch1
- Associative agnosia that is specific for faces
- May not recognize self, or familiar friends and
family - Dissociation between face recognition and object
recognition - Are faces special?
54Material not covered in class
55Auditory Perception
56Ear Anatomy
- Outer Ear
- Inner Ear
- Middle Ear
- Eardrum
- Ossicles
- Semicircular Canals
- Cochlea
- Oval Window
- Basilar Membrane
- Hair Cells
- Organ of Corti
- Round Window
- Auditory Nerve
57Auditory Sensory Memory
- Also known as Echoic memory.
- Studying ASM
- Three-eared man technique
- Modality Effect
- Suffix Effect
58Auditory Pattern Recognition
- Templates
- --the problem of invariance?
- Feature Detection
- Conceptually Driven Processing
- --Warren and Warrens (1990) study
59Summary of Major Topics Covered in Chapter 3
- Visual Perception
- Pattern Recognition
- Object Recognition
- Agnosia
- Auditory Perception