Week 4: Sensation & Perception PDF

Week 4: Sensation & Perception Prosopagnosia: sensing & perceiving are connected, but different Prosopagnosia Cognitive disorder of face perception Diffi...

Week 4: Sensation & Perception Prosopagnosia: sensing & perceiving are connected, but different Prosopagnosia Cognitive disorder of face perception Difficulty perceiving/recognizing faces Face blindness Intact vision Oliver Sacks, neurologist  Sensation & perception Sensation: detection of physical energy by the sense organs Perception: the brain’s interpretation of raw sensory data  Sensory systems Sensory receptors: specialized neurons that respond to different types of stimuli Our sensory systems provide information about our surroundings, allowing us to navigate and interact with our environments Photoreception: light Mechanoreception: pressure, vibration, movement Chemoreception: chemical  Transduction Conversion of one energy form into another RECEIVE SENSORY TRANSFORM THE DELIVER THE NEURAL INFORMATION VIA STIMULATION INTO INFORMATION TO THE SENSORY RECEPTOR NEURAL IMPULSES BRAIN CELLS (ACTION POTENTIALS)  The multitasking brain Bottom-up: perception based on building simple input into more complex perceptions Top-down: a perceptual process in which memory and other cognitive processes are required for interpreting incoming sensory information All you hvae to do is mkae a snetnece raedalbe is to mkae srue taht the fisrt and lsat letrtes of each word saty the smae.  Sensory adaptation Activation is highest at first detection, then sensory adaptation occurs Sensory receptor cells become less responsive to a stimulus that is unchanging, becomes less noticeable Adaptive — conserve energy, focus on novelty & changes!  Psychophysics: the measurement of sensation Sensation begins with a detectable stimulus Absolute threshold: minimum intensity of a stimulus that a person can detect half the time 1 tbsp of A candle 48 sugar in km away on 7.5 L of a clear night water Subliminal perception Perception of stimuli that are presented at below absolute threshold Perception ≠ persuasion, little practical application (e.g., self-help tapes)  Just Noticeable Difference (JND)/Difference threshold The degree of difference that must exist between two stimuli before the difference is detected Many decisions rely on our ability to detect small differences! 40 dB 45 dB Weber’s law: JND between 2 stimuli is not an absolute amount, but an amount relative to the intensity of the first stimulus. 110 dB 115 dB The more intense the initial stimulus, the larger the difference needs to be  JND & Marketing JND applies to what we buy! Marketers are concerned that: Positive changes are discernible (at or just above JND) Negative changes are not discernible (below JND) Changes subtle enough to keep current customers The role of attention in S&P Flexible attention is critical! Selective attention Focusing on a specific aspect of sensory input while ignoring other stimuli in the environment Attention as bottleneck The other channels are still being processed at some level Cocktail party effect  The role of attention in S&P We are poor at detecting stimuli in plain sight if our attention is focused elsewhere! Inattentional blindness Failure to detect an unexpected stimulus in plain sight Limited attentional resources, focus on what we deem important The role of attention in S&P Change blindness Failure to detect changes in your environment Limited resources further constrained by… Age Distraction Simons & Levin (1998)  Inattentional & change blindness: real world examples Davies & Hine, 2007; Hyman et al., 2009; Nelson et al., 2011 Senses Vision Vision starts with light, the physical energy that stimulates the eye Transduction: photoreceptors (rods & cones) The eye Retina: light-sensitive back inner surface of eye – nerve Iris: muscle ring that controls cells here! pupil size Contains rods & cones Controls amount of light entering eye (via the pupil) Optic nerve: carries neural impulses from eye to brain Cornea: light enters through Blind spot: point where optic cornea, passes through pupil, nerve leaves the eye, no and hits lens receptor cells Lens: Focuses light rays into image on eyeball’s retina  The eye: vision’s window Iris’ main job is controlling light that enters BUT also… The eye adjusts to imaginary light! Iris constricts with disgust or when you’re about to say “NO” Dilates with romance or trust (autonomic arousal) Find your blind spot Scan the QR code Rotate your phone/tablet horizontally Close your left eye and look directly at the dot – bring the phone closer and farther away from your face until the cross disappears – this is your blind spot! Rods & cones Retinal receptors Rods (100-125 mil): detect black, white, and gray and are sensitive to movement Peripheral & twilight vision Low light situations Located in periphery Cones (5-6 mil): sharp focus, colour perception, detail Work well in daylight Cluster around fovea Experience the rod-cone difference Look at or near any of the 12 black dots and you can see them, but not in your peripheral vision. Vision: How We Perceive Shape and Contour Feature detectors: cells in visual cortex that respond are sensitive to specific features of env’t Some cells respond to lines in specific orientations Simple cells – lines, angles Some cells respond to particular shapes (e.g., bulls-eyes, spirals, faces) Colour vision Different theories of colour perception Trichromatic theory: retina contains red, green & blue receptors – when stimulated, these receptors can produce perception of any colour Consistent with three types of cones in eyes Explains colour blindness BUT not afterimages Colour blindness Colour vision Opponent process theory: we perceive colours in terms of three pairs of opponent colours: red or green, blue or yellow, and black or white Colour vision Colour processing combines the trichromatic theory and the opponent processing theory Two stages: The retina’s red, green, and blue cones respond in varying degrees to different colour stimuli The cones’ responses are processed by opponent-process cells When we can’t see Blindness can result in reorganization of other sensory cortices and changes in other senses (i.e., compensation) Echolocation might improve following blindness Visual agnosia: object recognition deficit: damage to higher visual cortical areas Blindsight: above-chance visual performance of cortically blind individuals with damage to area V1 Visual agnosia Perceptual organization How do we organize and interpret sights so they become meaningful perceptions? Perception is a constructive process – we go beyond the stimuli that are presented to construct a meaningful situation! We don’t passively respond to visual stimuli that fall on the retina, we actively try to organize and make sense of what we see Gestalt Principles Principles that determine how we organize information into meaningful wholes We are born with built in tendencies to organize incoming sensory info in certain ways “the whole is more than the sum of its parts”  Peeled faces (closure) The Papal Palace (proximity) Perceptual constancy The recognition that objects are constant and unchanging even though sensory input about them is changing Moon appears larger when it is close to the horizon due to perceptual cues! High in the sky = by itself Near horizon = perceptual cues of terrain and objects produce misleading sense of distance Perceptual constancy Colour Constancy The ability to perceive an object as having relatively the same colour under varying illumination conditions Illusion can occur when this adjustment leads to misperception of colour!  How do we perceive depth? Monocular depth cues rely on one eye, e.g: Relative size Texture gradient Overlap Shading Height in field of view Linear perspective Depth & distance perception Binocular depth cues require both eyes Convergence Disparity Depth Perception Visual cliff Hesitation as young as 6 months old Demonstrates that depth perception is partly innate and a result of experience Culture shapes visual attention (top-down) East Asians & European/North Americans process visual information differently! Eastern à holistically (context & relationships) Western à analytically (salient objects) Hearing (audition) Sound is movement of air molecules brought about by vibration of an object Physical aspects of sound Frequency = pitch (Hz) Amplitude = loudness (dB) Hearing loss & hearing damage Sensing sound (1) The outer ear (pinna) Reverse megaphone – funnels sound in toward eardrum Eardrum (aka Tympanic membrane) Part of the ear that vibrates when sound waves make contact Transmits vibrations to middle ear Middle ear Tiny chamber containing 3 tiny bones (stirrup, anvil, hammer) that act as mechanical amplifier Sensing sound (2) Cochlea Hair cells Coiled tube in ear filled with Tiny cells that are bent by fluid that vibrates in response vibrations – transmit neural to sound message (transduction happens here!) Basilar membrane Runs through center of cochlea – divided into two chambers, covered with hair cells  Infant hearing program When we can’t hear Conductive deafness: malfunctioning of the ear especially a failure of eardrum or ossicles Nerve deafness: due to damage to auditory nerve Nerve-induced hearing loss: damage hair cells due to repeated loud noises Sociocultural influences on auditory perceptions Culture & social life provide framework for interpretation of stimuli Sine wave speech experiments – what people hear depends on expectations  The Multitasking Brain Bottom-up processing Begins with sensory receptors We sense basic features of stimuli and integrate them Top-down processing Guided by higher-level mental processes Previous experience and expectations are used to interpret what senses detect Perception is built from senses and influenced by experiences, biases, and culture. Perceptual sets Predisposition or readiness to perceive something in a particular way (top-down influence) Experiences, expectations, emotions etc.  Perceptual sets: examples M IT Lee at al., 2007 Robinson et al., 2007  Context effects on perception Recall your own perceptions in different contexts (e.g., driver versus pedestrian) Context helps form perception and interpretation of a situation  Cultural context effects Gregory & Gombrich, 1973  Emotions can sway our perceptions Sad music predisposes us to Anger increases likelihood Worrying about panic leads perceive sad meanings that neutral items will be to interpreting physical (mourning vs. morning) mistaken as a weapon sensations as panic Halberstadt et al., 1995; Balcetis & Dunning, 2006; Proffitt et al., 2003  Motives & perception Desired objects Closeness can seem closer when increase desire motivated Balcetis & Dunning, 2010; Shin et al., 2019 Social distancing, loneliness & perception of social threat COVID-19 lockdowns In UK, within a few weeks of lockdown # of adults who reported loneliness doubled, 18 – 24 at highest risk Loneliness is driven by perception! Perception of one’s social life falling short of expectations (i.e., you can still have many friends) Lonely people are more sensitive to social threats (e.g., images of social rejection Social distancing --> loneliness à sensitivity to social threats  Bias & perception Children as naïve, innocent, afforded certain protections Goff et al., (2014) Perceptions of age can be influenced by race 264 university students involved in the study Overestimated the age of Black children by 4.5 years (i.e., 12 à 16-year-old) Black children over the age of 10 judged as significantly “less innocent” than white children of the same age. Associated with anti-Black prejudice & dehumanization Cross talk between senses Many examples McGurk effect Rubber hand illusion Synesthesia Stimulation of one sense evokes another Sounds with colour, colours with taste Synesthetes "I have a condition called synesthesia where I see sounds. Everything I sonically make is a painting. I see it. I see the importance and the value of everyone being able to experience a more beautiful life.”