1. Perceptual Processes I (Ch 2)
Cognition: Lecture 3
Perceptual Processes I (Ch 2)

2. Perceptual Processes: Visual & Auditory Recognition
Overview of today’s lecture
Finish lecture from last class
Theories of visual object recognition
Bottom-up and Top-down processing
Top-down processing and smart mistakes
Face perception
AI and object recognition
Auditory recognition

3. Top-Down Processing: Smart Mistakes
Overactive top-down processing can lead to smart mistakes
Change Blindness
Failure to detect a change in an object or scene
Stranger-and-the-door study
Inattentional Blindness
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

4. Top-Down Processing: Smart Mistakes
How can we reconcile these errors with theme 2?
“Cognitive processes are remarkably efficient and accurate”
Visual stimuli are not high in ecological validity
Visual system is not a recording device
We get the ‘gist’ and focus on important stimuli
Ignore unimportant details
Cognitive errors are due to a rational strategy

5. Face Perception
A unique form of object recognition?

6. Face Perception Most socially significant form of recognition
Should be a difficult task
Faces have similar shapes, features, coloring
Visual stimuli is not constant
Changes in expression
Recognition from a distance and different angles

7. Face Perception Applied research on face perception
Focuses on real-life situations that assess our ability to recognize people’s faces
High ecological validity
What has this research shown us?
We tend to recognize faces differently than objects
Facial recognition abilities appear to be well developed at birth
Distinct neural circuitry

8. Face v Object Recognition
Faces perceived holistically (Gestalt) not by features
Tanka & Farah (1993)
Participants significantly more accurate in recognizing facial features in the context of a whole face
Same participants also judged parts of a house
Accuracy equal alone or as part of a house L

9. Face v Object Recognition
Accuracy of facial recognition
These ‘smart mistakes’ may relate to our difficulty in recognizing individual facial features
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)
Video of known and unknown professors (Burton et al., 1999)

10. Face Perception: Infants
Studies of young infants suggest that face perception is ‘special’
Aprox. 9 min post birth infants will show eye and head turns in response to moving stimuli (Coren et al., 1975)
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)

11. Face Recognition: Neuroscience Research
Much research on individuals with prosopagnosia (face blindness)
A disability in which individuals cannot recognize faces but can recognize objects relatively normally
Individuals often report various elements of face seem independent as apposed to unified
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)

12. Face Recognition: Neuroscience
Additional Agnosia’s
Simultagnosia
Unable to perceive multiple objects in visual field.
Focus on single object. ‘Can’t see the forest for the tree’
Achromatopsia
An inability to distinguish colors
These are due to problems in perceptual processing

13. Face Recognition: Neruroscience
Face-Inversion Effect (D’Esposito et al., 1999)
Faster brain response to faces in upright positions
Loss of face perception proficiency when inverted
Evidence for localized brain module for upright faces:
E.g., fusiform gyrus a portion of the inferotemporal cortex
Ind. with prosopagnosia have better performance with inverted faces

14. Object Recognition and AI
Visual object recognition seems effortless but this is something the field of AI has struggled with
Computer vision
Science of making computers see and understand what they see
Important practical applications:
Recognition of postal codes
Facial recognition
Image Search
Autonomous Cars

15. Auditory Recognition

16. Auditory Recognition: Speech Perception
Like visual object recognition auditory recognition is extremely complex
Speech perception requires the auditory system to:
register sound vibrations
translate vibrations into a sequence of sounds
We perceive about 900 phonemes per minute during speech
distinguish the sound pattern of one word from irrelevant words
separate voice of speaker from background noise

17. Characteristics of Speech Perception
Phoneme
The basic unit of spoken language
The smallest unit of language (sound)
Ie., Bat v But differ by /a/ and/u/ phoneme
English includes phonemes
Other languages use different sets of phonemes

18. Characteristics of Speech Perception
Important characteristics of speech perception
Listeners impose boundaries b/t words
A pause marks a word boundary approx 40% of the time
For English speakers we hear clear boundaries between words but non-English speakers do not hear these pauses
Listen to these phrases
How many words are in this sentence?

19. Characteristics of Speech Perception
Important characteristics of speech perception
Variability in phoneme pronunciation
Phonemes can sound very different depending on the speaker
Ie.,pitch, tone, rate of speech production, accent
Phonemes not produced in a precise fashion
Coarticulation: the articulation of two or more speech sounds together, so that one influences the other
Dean v Beat

20. Characteristics of Speech Perception
Important characteristics of speech perception
Context allows listeners to fill-in missing sounds (Phonetic restoration)
Waren & Waren (1970)
It was found that the *eel was on the axel
It was found that the *eel was on the shoe
It was found that the *eel was on the orange
*cough
Participants view the sentence as complete with contextually appr. word
Unable to report missing

21. Characteristics of Speech Perception
Important characteristics of speech perception
Visual cues aid in speech perception
Visual cues (e.g., lip movements) are normally not necessary; however, this info is useful with ambiguous sound
McGurk Effect (McGurk & McDonald, 1976)
Recorded voice articulating a consonant and a face articulating a different consonant
Voice: Gag
Face: Bab
Person reports: Dad
This is compromise or ‘fusion’ of the conflicting sensory input

22. Characteristics of Speech Perception
Two main approaches to speech perception
Speech is special (Special Mechanism Approach)
Suggests that humans are born with a special device that allows them to decode speech stimuli
Phonetic/Speech module
Evidence For
Categorical Perception
Phonetic information in between b or p sound perceived as p or b

23. Characteristics of Speech Perception
General Mechanism Approach
Argues we perceive speech sounds using processes similar to non-speech sounds
Categorical processing for speech and non-speech sounds
Facilitation of speech recognition by visual cues suggest there is not a distinct phonetic module