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Cognition: Lecture 3
Perceptual Processes I (Ch 2)
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Perceptual Processes: Visual &
Auditory Recognition
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Overview of today’s lecture
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Finish lecture from last class
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Theories of visual object recognition
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Bottom-up and Top-down processing
Top-down processing and smart mistakes
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Face perception
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AI and object recognition
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Auditory recognition
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Top-Down Processing: Smart
Mistakes
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Overactive top-down processing can lead to smart mistakes
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Change Blindness
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Failure to detect a change in an object or scene
Stranger-and-the-door study
 https://www.youtube.com/watch?v=VkrrVozZR2c
Inattentional Blindness
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Failure to notice an unexpected but visible object when attending to
something
People are more likely to make intentional blindness errors if the task
is more cognitively demanding
Monkey Business Illusion
 https://www.youtube.com/watch?v=IGQmdoK_ZfY
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Top-Down Processing: Smart
Mistakes
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How can we reconcile these errors with theme 2?
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“Cognitive processes are remarkably efficient and accurate”
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Visual stimuli are not high in ecological validity
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Visual system is not a recording device
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We get the ‘gist’ and focus on important stimuli
Ignore unimportant details
Cognitive errors are due to a rational
strategy
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Face Perception
A unique form of object recognition?
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Face Perception
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Most socially significant form of recognition
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Should be a difficult task
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Faces have similar shapes, features, coloring
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Visual stimuli is not constant
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Changes in expression
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Recognition from a distance and different angles
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Face Perception
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Applied research on face perception
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Focuses on real-life situations that assess our ability to recognize
people’s faces
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High ecological validity
What has this research shown us?
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We tend to recognize faces differently than objects
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Facial recognition abilities appear to be well developed at birth
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Distinct neural circuitry
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Face v Object Recognition
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Faces perceived holistically (Gestalt) not by features
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Tanka & Farah (1993)
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Participants significantly more accurate in recognizing facial
features in the context of a whole face
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Same participants also judged parts of a house
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Accuracy equal alone or as part of a house
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Face v Object Recognition
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Accuracy of facial recognition
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These ‘smart mistakes’ may relate to our difficulty in recognizing
individual facial features
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93% of the time cashiers accepted ID from actual person; 64% of the time
they accepted ID from similar looking person (Kemp et al., 1997)
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Video of known and unknown professors (Burton et al., 1999)
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Face Perception: Infants
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Studies of young infants suggest that face perception is
‘special’
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Aprox. 9 min post birth infants will show eye and head turns in
response to moving stimuli (Coren et al., 1975)
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Greater response to face pattern than scrambled face or blank
A few hours after birth newborns can discriminate between faces
and prefers mother’s face (Bushnell et al., 1989; Pascalis et al.,
1995)
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Face Recognition: Neuroscience
Research
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Much research on individuals with prosopagnosia (face
blindness)
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A disability in which individuals cannot recognize faces but can
recognize objects relatively normally
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Individuals often report various elements of face seem
independent as apposed to unified
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Damage to the fusiform gyrus a portion of the inferotemporal
cortex
"Fusiform gyrus animation" by Polygon data were generated by Database
Center for Life Science(DBCLS)
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Face Recognition: Neuroscience
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Additional Agnosia’s
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Simultagnosia
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Unable to perceive multiple objects in visual field.
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Focus on single object. ‘Can’t see the forest for the tree’
Achromatopsia
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An inability to distinguish colors
These are due to problems in perceptual processing
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Face Recognition: Neruroscience
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Face-Inversion Effect (D’Esposito et al., 1999)
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Faster brain response to faces in upright positions
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Loss of face perception proficiency when inverted
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Evidence for localized brain module for upright faces:
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E.g., fusiform gyrus a portion of the inferotemporal cortex
Ind. with prosopagnosia have better performance with inverted
faces
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Object Recognition and AI
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Visual object recognition seems effortless but this is
something the field of AI has struggled with
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Computer vision
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Science of making computers see and understand what they see
Important practical applications:
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Recognition of postal codes
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Facial recognition
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Image Search
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Autonomous Cars
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Auditory Recognition
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Auditory Recognition: Speech
Perception
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Like visual object recognition auditory recognition is
extremely complex
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Speech perception requires the auditory system to:
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register sound vibrations
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translate vibrations into a sequence of sounds
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We perceive about 900 phonemes per minute during speech
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distinguish the sound pattern of one word from irrelevant words
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separate voice of speaker from background noise
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Characteristics of Speech
Perception
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Phoneme
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The basic unit of spoken language
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The smallest unit of language (sound)
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Ie., Bat v But differ by /a/ and/u/ phoneme
English includes 40-45 phonemes
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Other languages use different sets of phonemes
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Characteristics of Speech
Perception
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Important characteristics of speech perception
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Listeners impose boundaries b/t words
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A pause marks a word boundary approx 40% of the time
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For English speakers we hear clear boundaries between words
but non-English speakers do not hear these pauses
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Listen to these phrases
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How many words are in this sentence?
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Characteristics of Speech
Perception
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Important characteristics of speech perception
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Variability in phoneme pronunciation
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Phonemes can sound very different depending on the speaker
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Ie.,pitch, tone, rate of speech production, accent
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Phonemes not produced in a precise fashion
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Coarticulation: the articulation of two or more speech sounds
together, so that one influences the other
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Dean v Beat
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Characteristics of Speech
Perception
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Important characteristics of speech
perception
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Context allows listeners to fill-in missing
sounds (Phonetic restoration)
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Waren & Waren (1970)
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It was found that the *eel was on the axel
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It was found that the *eel was on the shoe
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It was found that the *eel was on the orange
*cough
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Participants view the sentence as complete
with contextually appr. word
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Unable to report missing
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Characteristics of Speech
Perception
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Important characteristics of speech perception
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Visual cues aid in speech perception
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Visual cues (e.g., lip movements) are normally not necessary;
however, this info is useful with ambiguous sound
McGurk Effect (McGurk & McDonald, 1976)
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Recorded voice articulating a consonant and a face articulating a
different consonant
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Voice: Gag
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Face: Bab
Person reports: Dad
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This is compromise or ‘fusion’ of the conflicting sensory input
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Characteristics of Speech
Perception
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Two main approaches to speech perception
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Speech is special (Special Mechanism Approach)
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Suggests that humans are born with a special device that allows
them to decode speech stimuli
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Phonetic/Speech module
Evidence For
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Categorical Perception
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Phonetic information in between b or p sound perceived as p
or b
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Characteristics of Speech
Perception
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General Mechanism Approach
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Argues we perceive speech sounds using processes similar to
non-speech sounds
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Categorical processing for speech and non-speech sounds
Facilitation of speech recognition by visual cues suggest there is
not a distinct phonetic module