Perception - COGS 200 IWA3

Lecture 11; Feb 27 Perception

• In Human Brain

  • Specialized interfaces for each sensory modality with different senses projecting to different brain regions

Vision

• How visual info travels from eyes to brain (Primary Geniculostriate Pathway)

  • Enters through retinal

  • Goes through optic nerve, chiasm, tract

  • Passes through thalamus

  • Optic radiations spreads into multiple channels

  • Arrives at multiple inputs at primary visual cortex V1

• Visual representations in V1

  • Feature detectors; system responding to presence of specific pattern in stimulus 

    • Ex. Specific shape, colour, direction of motion

      • Seeing world as simple line  drawing

      • Colour info present but not integrated

  • Beyond V1

    • Info from V1 passed first to V2 then onward 

• Functional specialization

  • Optic array has many kinds of info like shape, colour, motion, depth

  • Different neural pathways and areas are responsible for processing these info

• Vision for Perception; Ventral Stream

  • Temporal lobes

  • The “what” pathway

  • Connecting sensation to memory

    • Early visual areas in occipital lobe to memory centres in medial temporal lobe

  • Ventral processing; visual illusions

    • Perceptual system takes shortcuts to process things more efficiently

    • Tricks which make perception effective lead to inaccuracies when regularities are violated

    • Size constancy; something far from retinal casts same size retinal image as something close 

      • Far item is bigger than near item

      • Terror Subterra Illusion

      • Ames Room Illusion

    • Afterimages; shows that neural circuits in perception are often faired in opponent pair

      • Cells have specialized stimuli and after long exposure cells become fatigued responding less

        • Opponent wins by default

    • Troxler fading; shows how our perceptual system is designed to detect change

      • We stop processing static things and stop perceiving them at all

      • Efficient way to handle info as only new info is worth processing

    • Motion induced blindness 

    • Apparent motion 

    • Lilac chaser; combo after images and apparent motion

    • Flashing light (Magic Light)

    • Shadow cues

    • Illusion shows how sensory info isn’t perfect

    • Brain relies on heuristics to make sense of world

    • Mistakes in perceptions are illusions

  • Ventral stream; faces are special

    • Invariant aspects; 2 eyes, noses mouth

    • Changeable aspects; expressions

    • Fusiform face area; face selective

    • Familiarity effect; easier to recognize people the more familiar they are

    • Hollow Mask Illusion; experience with face perception leads to hollow mask illusion

    • Prosopagnosia; can’t recognize faces

    • Pareidolia; seeing faces where they don’t exist

    • Faces at perceived holistically via all features together

    • When faces are inverted holistic process is disrupted and fineness feature ok individually so don’t notice configuration problems 

  • Summary of face perception

    • Our skill in distinguishing faces is remarkable (and can be distorted)

    • Familiar faces are perceived more efficiently than faces of strangers

    • It is virtually impossible to see a “hollow” face (hollow mask illusion)

    • We often see faces in non-face images (face pareidolia)

    • We are more efficient in processing upright faces than inverted faces

• Vision for Action; Dorsal stream

  • Parietal lobes

  • The “how” pathway

  • Patient DF; ventral lesion

  • Ebbinghaus Illusion

    • Perceptual judgements(ventral stream) are readily fooled by Ebbinghaus illusion

      • Grasping actions aren’t influenced at all(dorsal stream)

  • Action intention affecting vision

    • Faster detect change in large object with power grip 

    • Faster detect change to small object with precision grip

  • Perihand space

    • Perihand; near or around hands

      • When far, ventral is useful info about identity

      • When near, dorsal important 

      • Moving object into Perihand space can improve visual processing in the case of lesions(brain damage)

  • From eyes to brain

    • Contralateral cortex

      • Ex. Left visual field processed on right side of brain

Lecture 12; Mar 4 Perception of Language

• Cognitive Science

  • Goal; develop theories of mind which are falsifiable along with research methods for testing these theories

• Classical Cognitive Science

  • Computational theory of mind

    • Not the view that the mind is like a computer (mind software, brain hardware)

  • View that the mind is a computational system enabled by brain’s neural activity

    • Computation (in classical cogs meaning); Turing machines

    • Turing machines; abstract computational machines which manipulated symbols according to rules and internal states

      • Has infinite memory space

      • Machine physical details do not matter

        • Computation implementable regardless of physical details

        • Mind = computational system

• Basic tenets of classical cognitive science

  • Thinking is conceptually like computation

  • Intelligence involves mental manipulations (based on rules) of mental representations (concepts of world)

    • Concepts enable knowledge categorization

    • Mental states are also representations

  • Some aspects of mind are not computational (emotions)

• The mind according to classical cognitive science

  • Mind is sole locus of cognition

    • CNS acts as conductor telling rest of body what and how to do it

  • Inputs mind gets from bodies are impoverished forcing brain to fill in blanks with inferences

  • Cognition is a manipulation of symbolic structures which are amodal, abstract, combinatorial

• The Stroop Effect

  • Saying out loud what the colour of the following words as quickly as possible

  • Delay in reaction time between congruent and incongruent stimuli

    • Semantic interference; longer reaction time if colour of word mismatches meaning of word

    • Semantic facilitation; faster reaction times if colour of words matches meaning of word

• The McGurk Effect

  • Perceived; Da da da da da da

  • Audio; Ba ba ba ba ba ba

  • Visual; Ga ga ga ga ga ga

  • Doesn’t work with familiar faces

• Multimodal perception

  • What you see influences what you hear

  • Brain integrates info from auditory and visual modalities

  • Automatic

• Multimodal integration in speech

  • Visual info from face interferes with auditory perception

    • Due to receiving 2 info at same time so unconsciously associate on with the other

  • Tactile info is also important

• Tactile info interferes with speech perception

  • Ex. English has some tiny bursts of aspiration

    • Gick and Derrick applied slight air puffs on right hand or neck

      • Tend to mis hear as a sound that is aspirated

      • Ex. b to p

    • Indirect aspiration can cause people to mishear unaspirated as aspirated

• Visuo-tactile integration in speech

  • 4 conditions; pom vs bomb, with and without candle flicker

  • Associations are learnt very early in language acquisition

    • Keough, Kadhadai, Werker, Gick; replicated puff study with preverbal infants who haven’t started babbling yet

    • Lewkowicz and Hansen Tift; showed infants of 4-8 months of age look at mouths of speaking adults

      • Start looking more at eyes around 12 months

      • If speaking with unfamiliar language, look at mouth

      • Looking at mouths allows access redundant audiovisual speech cues

• Phonemic restoration effect

  • Missing speech sounds are restored by brain and appear to be heard

    • Doesn’t occur when phonemes are just missing

      • Occurs when replaced by noise

      • Brain interprets ambiguous auditory signal as an unambiguous auditory signal 

      • Children show these effects around age 5

• Auditory brain activation without auditory input

  • Brain areas associated with auditory processing activate even when people view silent visual speech

    • No such activation when viewing nonspeech lip and jaw movements

    • Visual info can influence auditory cues processing before categorized into phonemic categories

• Categorical perception

  • Perceptual phenomenon when variable gradually changes on a continuum perceived categorically

    • In speech perception, phenomenon mostly applies to perception of phonemes

    • Cannot discriminate between similar sounds unless at category boundary

  • Voice onset time; movement of physical mouth lips to vocal chords

• Perceptual narrowing

  • Developmental process resulting from neuroplasticity

    • Exposure to experiences shapes perception

  • Narrowing; ability to perceive something we are rarely exposed to

  • Newborns can distinguish all possible phonemes of all human languages

    • Declines and disappears if not exposed to these foreign languages

• Superadditivity

  • Additive; 1 + 1 = 2

  • Superadditive; 1 + 1 > 2

  • Multisensory speech perception is more than a sum of unimodal parts

    • More accurate to audio visual cues than expected sum of responses to visual and auditory cues

• Conclusion

  • Speech perception is multimodal

  • Sensory info can derive from unexpected sources

  • Learn associations between sensory info and correspond speech properties very early in life

  • Possible due to brain plasticity

  • Subsequent perceptual narrowing makes our perception of phonemes categorical

Readings for Lecture 12

Warren (1970) Perceptual Restoration of Missing Speech Sounds

• Experiment; 20 undergrads tested given a stimulus of a tape recording of a sentence

  • Small section deleted and replaced with a cough of the same duration

    • After listening to a cough occurring elsewhere, circle exactly where cough occurred and weather replace or fully replaced

      • All reported speech sounds were present

      • No one chose correct cough position

• Phonemic restoration is linked to language skills enabling listening to detect correct sound

  • When speech sound deleted and not replaced with extraneous sound - gap recognize in proper location

    • Illusory perception did not occur

  • Our lack of awareness of restorative processes and illusory perception of speaker’s utterance shows the perceptual mechanisms underlying verbal organization

Francois Grosjean (2015) When Bilingual Infants look at people talking

• David Lewkowics and Amy Hansen Tift study on infant eye gaze

  • Monolingual Infants watched person utter an english monologue on computer monitor

    • Used eye tracker to see where baby looked

    • 2 main areas on speaker’s face

      • Around eyes and around mouth

        • 4 months old; looked longer at eye

        • 8 months old; looked longer at mouth

          • Learning how to speech so attracted by auditory and visual speech signals

        • 12 months old; equal time

          • Less need to access visual speech cues

          • Focus on social cues

• Ferran Pons and Laura Bosch and Bilingual infants

  • Hypothesis; as need to process 2 languages, use audiovisual speech cues more

    • 4, 8, 12 months similar results for dominant language

    • For secondary language

      • 4 months; equal

      • 8 months; longer mouth

      • 12 months; longer mouth

      • Exploited perceptual info of these cues earlier and longer than monolingual infants

Readings for Lecture 13

• Overview of Epistemology

  • Epistemology; knowledge, truth, memory, and perception

    • Truth is essential to knowledge

    • Memory and perception are crucial in knowledge acquisition

      • Perception; allows us to gain knowledge about the world

      • Memory; retains this knowledge over time

• The problem of visual cognition

  • Science has advanced in understanding how we know things but philosophical issues remain unresolved

  • Philosophical problems are difficult as they resist straightforward scientific solutions 

    • Ex. nature of perception

  • Influence of computer science and info processing models has reshaped the discussion

    • Core issues are the same as those debated by John Locke and early philosophers

• Distinction between seeing objects vs seeing facts

  • Seeing objects; perceiving physical entities

  • Seeing facts; knowing what is seen means something

• Implications for cognitive science

  • Visual perception involves recognizing facts

  • Cognitive perception involves recognition and understanding whereas sensory is mere exposure to visual stimuli

    • Example in cognitive psychology; recognizing a triangle requires realizing it has 3 sides

      • Seeing a shape without knowing it is a triangle is not full cognitive perception

Perceptual objects and knowledge hierarchy

• Mediated vs direct knowledge

  • Many things we see are understood through other perceptions

    • Ex. see we need gas by seeing fuel gauge

  • Some knowledge depends on other knowledge

    • Ex. seeing a frown you will know someone is unhappy

• Direct vs indirect knowledge

  • Some philosophers argue that all knowledge of external reality comes from subjective experiences (only see subjective representations)

  • Ex. seeing a newspaper report about a plane crash

    • Direct or indirect knowledge?

• Skepticism and visual perception

  • Skeptical argument

    • If perception is mediated by subjective experiences can we ever be certain of what we see

    • Dretske’s response

      • Can still see objects even if we don’t know for certain what they are

      • Ex. child can see a cat but mistake for a sweater but still see something real

Theories of Perception

• Direct Realism

  • View; we perceive objects directly as they exist in the world

  • Key idea; objects exist independently of our perception and we see them as they truly are

  • Objection; this ignores illusions, hallucinations, and distortions in perception

    • How to explain cases where perception misleads us

• Representative (indirect) Realism (causal theory of perception)

  • View; we don’t directly perceive objects but instead perceive mental representations of them

  • Key idea; our brains make internal representations of the world based on sensory input

  • Ex; watching a game on TV -> aren’t seeing actual game but rather image of it

  • Objection; if only perceive representations, how can we confirm they accurately reflect reality

• Idealism (Phenomenalism)

  • View; there is no external reality perception everything and everything is a mental construct

  • Objection; radical view is not widely accepted as implies reality does not exist independently of our minds

• Mixed (hybrid) position

  • View; we may perceive physical objects directly (direct realism) but only know them through mental processing (indirect realism)

  • Problems; how do we know how objects look without perceiving our own internal mental images?

    • Debate on nature of sensory vs cognitive perception

• Sensory perception vs cognitive perception

  • Sensory perception; seeing an object without knowing what it is

  • Cognitive perception; recognizing an object as what it is

  • Debate; is there pure sensory perception or is all perception cognitive in some way

    • Can we see something without having any knowledge of what it is

Lecture 13; Mar 11 Sensation and Perception in the Mind

• Goodale and Milner (1992)

  • Optic ataxia;  dorsal path is damaged but ventral is not

    • Subject may say what angle a mail slot is but cannot visually guide hand to correct angle

  • Visual form agnosia; if ventral pathway (vision for perception) is damaged but dorsal is not 

    • Eyes may be able to guide hand to correct angle despite not knowing what the angle is

    • Seeing may not count as perceiving unless goes along ventral pathway to temporal lobe

• Dretske (1990); Seeing, Believing, and Knowing

  • Sensory perception (object vision)

  • Cognitive perception (fact vision)

    • Argues possibility to object see something without fact seeing it (See vs perceive/understand)

• Difference blindness

  • Change blindness

    • Do see difference but don’t know see a difference

• Phonemic restoration effect (filling the gap)

  • Brain fills in absent phonemes to replace the extraneous sound

    • Fill in (gap) of auditory experiences (percept)

      • Brain uses some figment to do filling in

• Classical sandwich model

  • • Agent is distinct from but interacts with its environment

      • 2 kinds of interface between the agent and environment

• Cognitive systems

  • Perception; forms one interface between agent and environment

  • Knowledge representation; memory (data structures) and reasoning (program) are central

  • Action; (behaviour) forms the other interface

• Human Cognitive Systems

  • Representational states and rational processes; acquiring, retaining, and employing info

  • Unified in a way that constitutes a point of view/subjective experience

  • Private, not public

    • Tough to investigate empirically

    • Stimulus and response are mere evidence for cognitive activity

  • Free, autonomous, creative, and morally significant

• Nature of perception

  • Perception is a process that occurs in steps or stages

  • Produces generally accurate perceptual beliefs by means of sensations, images, visual appearances

    • ^ Indirect realism

      • Alternative view; direct realism

      • Drestke applies indirect account to cognitive perception (fact vision) but not to sensory perception (thing vision)

• Purpose of perception

  • Provides experiences of mostly accurate representations of scenes before us

    • Encounter objects in various arrangements

    • Encounters produces perceptual experiences in us which represent our environment

    • Form perceptual beliefs (knowledge representation memories) on basis of these experiences and how we interpret them

  • Muller Lyer Illusion

  • Wordsworth (1807) I wandered lonely as a cloud

  • Thomas Nagel (1974) What is it like to be a bat

    • No reductionist (objective) account of mind is possible

      • Something it is like to be a bat but won’t know from their POV

  • Epiphenomenal Qualia

    • Frank Jackson (1982) argues fully objective physical account of mind is incomplete

      • Mary (vision scientist) raised in black/white room learns all physical facts relevant to colour

        • But only sees colour for first time (learns new fact, what it is like to see red)

          • Physical facts are not all the facts there are about minds

  • Spectrum inversion

    • Same object should make several different ideas in each person at the same time

    • Private experience

      • Only difference is subjective experience of things

• Skepticism

  • By saying mind is a private sphere and our perceptual interactions with environment are indirect -> vulnerable to variety of traditional skeptical hypothesis

  • BIV (Brain in a vat) hypothesis

  • The “zombie” hypothesis

  • Mind body problem

  • Putnam; Reason, truth, and history

• How do you know you are not a brain in a vat?

  • Normal thought process

    • I see (hear, feel, remember) that I am in class now

    • So I know that I am in class now

  • New thinking

    • If I know that I am in class now, then I know I’m not a BIV

    • I don’t know I’m not a BIV

    • So I don’t even know that I am in class now

• Skepticism

  • If can’t cope with skeptical hypothesis → have no way to refute to them → look to underlying assumptions giving rise to skeptical worries

    • Inner area is mind → bad model?

• Nozick’s experience machine

  • Suppose an experience machine exists which can give any experience you desire whilst you float in a tank

    • Should you plug into the machine?

    • Nozick says no:

      • Argues desire to do things is greater than simply experience doing them

        • Watching youtube videos on rock climbing vs actually doing them?

      • Desire to be a certain person

      • Plugging in limits us to a man made reality

    • Cypher in the Matrix says yes:

      • Ignorance is bliss

• The Grand Illusion; ability to acquire and maintain a complete and accurate representation of the scene before us (imagination?)

  • Occurs via;

  • Objective stance; visual image is impoverished

  • Subjective stance; visual image is high definition, full colour

  • Deficits are not noticed but our visual experiences are not as complete as appears

Lecture 14; Mar 13 Perception (Psychology)

• Perception Recap

  • World gives a lot of info and only parts can be processed at a given moment

    • Perception fills in the gaps

  • Not all perception is done in the same way

    • What vs how (ventral and dorsal) streams

      • Some ventral illusions don’t produce illusory perception in dorsal stream

• Audition and Taste

  • Chips perceived as crisper and fresher with louder bite sound (and when high frequencies are amplified)

    • Chips into microphone study

      • Same amplification or lower sound

• Vision and Touch

  • Ex. Drumsticks held in either hand are tapped 1 after another with varying delays

    • Participant to judge which tap was first

  • With hands in a natural resting position, people do well

    • When either hands or sticks crossed, vision and touch conflict makes judgement more difficult

  • Rubber hand illusion

    • Strokes fake rubber hand and real hand at same time → only see rubber hand

      • Then stab the rubber hand → scary

  • The 2 visual pathways are not independent

• How does change blindness occur

  • Initially complete sensation but quickly forgotten

  • Not representation but comparison that fails

  • Initially complete sensation is recoded in a way that precludes comparison

  • Regardless of gaps, perception is a process/computation

• Grand Illusion

  • Perception is impoverished

  • Does not feel so subjectively

• Visual search

  • Interrupted visual search (look for 0.1s, wait 0.9s)

    • Search resumes after interruption

    • Use first glance to build prediction of what to see

    • Either confirm or receive error feedback and amend next prediction

• Predictive coding

• Social perception

  • Attribute mental states to geometrical shapes

  • Sensory input

    • Face identity

      • Expression, identity, gender, age socio-economic status

      • Sometime personality traits

      • Context is needed too

    • Voices, smell, body shape, fashion, what they are doing

    • Gaze info;

      • Can signal attentional state

      • Avoiding eye contact can suggest lack of confidence, feeling guilt or shame

      • Students avoid making eye contact when profs ask a question, don’t know content ot shy

      • If someone’s staring intently → wonder if try to intimidate, belittle, or love you

    • Other nonverbal cues

      • Body posture may show focus

      • Distance between people can infer friendly, intimate, or more distant

• Why is info not treated equally

  • Saliency

  • Cognitive bias; pattern in perception, interpretation, or judgement which is a systematic distortion of objectively available info

    • Negative cognitive bias; negative aspects of one’s behaviour has higher attention to

      • Negativity effect

      • May be due to prioritize survival and negative info is very salient

    • Positive cognitive bias; tendency to evaluate people positively 

      • Pollyanna hypothesis

      • Most behaviours one makes are likely positive as controlled by social norms

        • Ex. bad at lie detection

    • Halo effect; bias by which one attribute influences impression of other, unrelated attributes

      • Ex. Bob is nice → Bob is also smart

        • Can be positive or negative (sometimes called horn effect)

  • Categories and Schemas

    • Role schema; how people carry out certain roles

    • Person schemas; relates to certain types of people like profs, geeks, jocks

    • Event schemas; tells likeliness of occurring of things, when taking transit, going to party, lecture

    • Beneficial for quick access and ease of interaction

      • Also incomplete profiles mostly though

    • Challenges;

      • Cognitive biases (which tend to be inflexible)

      • Primacy effect

      • Belief perseverance; tendency to maintain one’s schema even with direct contradictory evidence

        • Reflets desire to maintain positive self image

      • Confirmatory hypothesis testing; unknowingly creating opportunities for own beliefs to be confirmed and ignore when beliefs are disproven