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

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 https://www.youtube.com/watch?v=VkrrVozZR2c 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 https://www.youtube.com/watch?v=IGQmdoK_ZfY

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

Face Perception A unique form of object recognition?

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

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

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

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)

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)

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)

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

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

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

Auditory Recognition

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

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 40-45 phonemes Other languages use different sets of phonemes

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?

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

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

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

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

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