Textbook Notes (362,767)
Canada (158,052)
Psychology (4,729)
Psychology 1000 (1,558)
Dr.Mike (659)

5 - Sensory and Perception.docx

13 Pages
Unlock Document

Western University
Psychology 1000

Chapter 5 Sensation and Perception Sensory Processes  Synesthesia: mixing of the senses o Experience sounds as colours o Tastes as touch sensations with different shapes o Women are more likely to experience this o Activity in one part of the brain evokes responses in another part dedicated to another sensory modality o Theory  Pruning of neural connections that occurs in infancy did not occur  Deficit to keep input from one sensory from inhibiting another sense and ends up stimulating it o Binding Problem: how do we bind all our perceptions into one while keeping sensory separate  Sensation o stimulus-detection process o sense organs respond to and translate environmental stimuli into nerve impulses that are sent to brain  Stimulus received by sensory receptors  Transduction - receptors translate stimulus properties into nerve impulses  Feature detectors: neurons break down, analyze features of stimuli once transduction occurs  Stimulus features are reconstructed into neural representation  Neural representation is compared with previously stored information in brain  Matching process results in recognition and interpretation of stimuli  Perception  Perception o Active process of making “sense” of what our senses tell us o Creative - same sensory input may be perceived in different ways at different times o Perception of characters influenced by context that preceded and followed them o How do we perceive the world around us?  Psychophysics  relation between physical stimulus and psychological response  Absolute limits/range of sensitivity  Fechner: “father” of psychophysics o Can determine a just noticeable difference (JND) in intensity  Psychophysiology  Stimuli of senses is different to each animal due to adaptation to environment in which it lives  Receptors in brain watch chemical composition of blood  Immune system can sense foreign invaders  Senses o Vision o Audition o Touch (pain, pressure, temperature) o Gustation (taste) o Olfaction (smell) o Balance and body position Stimulus Detection: The Absolute Threshold  Absolute Threshold: the lowest intensity at which a stimulus can be detected correctly 50% of the time o The lower the more sensitive Signal Detection Theory  factors that influence sensory judgements causing a person’s apparent sensitivity can fluctuate o Shows that perception is in part a decision  No fixed absolute threshold o No single point on intensity scale that separates nondetection from detection of stimulus  Decision Criterion: range of uncertainty, standard of how certain they must be that a stimulus is present The Difference Threshold  Smallest difference between two stimuli that people can perceive 50% of the time  Amount of change for just noticeable difference (jnd)  Weber’s Law: difference threshold or jnd is ∝ to magnitude of stimulus with which comparison is being made o The smaller the Weber fraction, the more sensitive  Most sensitive to brightness (1/60) o Size of difference threshold relative to physical intensity of test is constant o I = JND (consider ± values of I) I = starting value C = constant  Fechner’s Law o Sensation increases with the logarithm of intensity o S = k log O o Compare ∆I = CI o More general and cognitively economic o Linear relationship only works if very sensitive  Steven’s Power Law N o S = k log I  More predictive across a variety of sensations Sensory Adaptation  Sensory neurons respond to constant stimulus o decreasing activity and diminishing sensitivity to an unchanging stimulus  Habituation (adaptation)  Stabilized image o Maintain constant position on retina o Clear at first o Begins to fade and reappear in meaningful segments as receptors fatigue and recover The Neuroscience of Subliminal Perception and Prosopagnosia  Subliminal Stimulus: so weak or brief that it cannot be perceived consciously even though received by senses o Well below absolute threshold o Stimuli can affect attitudes and behaviour without us knowing  James Vicary o Experiment where flashed messages to drink coke and eat popcorn o Increased 50% sale o Consumer behaviour where persuasive stimuli is more influential than subliminal  William Tapley o In general, no evidence that subliminal cuts influence consumer behaviour  Bruce and Valentine (1986) o names are not very good aids for priming the recognition of objects or faces o prosopagnosia: cannot recognize faces  Fitzsimons et al. o 36 msec exposure to apple and IBM logo o The people exposed to apple logos were more creative in the task  J.K. Steeces o Recognize objects through colour and texture information but not size, shape and orientation o Can recognize objects by using other information even tho brain is damage  Biasing perception o subliminal cues can bias what we perceive consciously o may alter our conscious experience of those stimuli The Sensory Systems  Accessory structures - E.g. outer ear  Transduction - receptors  Coding - E.g. frequency  Interaction - Physiological and psychological Vision  Visual system sensitive in electromagnetic energy or light waves (violet) 400 nm – 700 nm (red) The Human Eye  Cornea o Focus light that enters through transparent protective structure at front of eye  Pupil o Behind cornea o Adjustable opening controlled by coloured iris that can dilate to let more light in when dark or constrict  Lens o Elastic structure behind pupil  Retina o lens focuses image on light sensitive area of this o multilayered tissue at rear of fluid-filled eyeball  Ganglion  Bipolar  Receptor - Output to optic nerve at the back of eye o Horizontal cell  Between receptors and bipolar  Enhance images and edges  Lateral inhibition – capacity of an excited neuron to reduce the activity of its neighbours  image is reverse from right to left and top to bottom when projected to retina  brain reconstructs the visual input into the image that we perceive  Phantom spots o Spectral sensitivity - caused by how eyes respond to light and dark areas o area is surround by light, your eye "turns down" the brightness  making you see darkened blobs due to inhibition of the central ganglion cell  Myopia: near sightedness, focus image in front of retina  Hyperopia: farsightedness, lens does not thicken enough so focuses on a point behind retina  Aging causes eyeball to shorten  hyperopia Photoreceptors: The Rods and Cones  Duplex theory o light level and dual retinal function and refers only to the rod and cone photoreceptor cell systems  Light sensitive receptors o Rods o Cones  120 million  6 – 7 million  best in dim light (low intensity)  best in bright light (high intensity)  Monochrome (Black and white)  Colour receptors  500 times more sensitive  Insensitive for brightness  E.g. night creatures (owls)  Eg. daytime creatures (pigeon)  Peripheral retina  Fovea (central retina)  Cannot pick up weak images  helps pick up weak images  Fovea: small area in centre of retina that contains only cones o Most sensitive part of retina o ↓ cones when farther from centre  Bipolar cells: synaptic connections with rods, cones o Ganglion cells:  Synapse with bipolar cells  axons form optic nerve  Rods, cones not only form rear layer of retina o Light sensitive ends point away from direction of entering light so receive only a fraction of light that enters eye  Many rods are connected to same bipolar cell o Additive effect may be enough to fire o Detect faint stimulus better if look to the side  Image does not fall on fovea but on peripheral portion where more rods  Cones in fovea have their own “private line” to a single bipolar cell o Visual Acuity: ability to see fine detail is greatest when the visual image projects directly onto fovea o Focusing causes firing of large number of cones and their private-line bipolar cells  Optic nerve through back of eye not far from fovea, producing a blind spot (no photoreceptors nor transductor) o Unaware of blind spot because perceptual system “fills in” missing part of visual field Visual Transduction: From Light to Nerve Impulses  Rods and cones translate light waves into nerve impulses through photopigments o Absorb light  chemical reaction  changes rate neurotransmitter release o ↑change in transmitter release = ↑ stronger signal passed to bipolar cell and in turn, to ganglion cells o If nerve responses are triggered at each of the three levels (rod/cone, bipolar, ganglion)  Instantaneous message to visual relay station in thalamus and then to visual cortex of the brain  How do they work? o Visual pigments  Photo sensitive  Break down when light hits them o Rods: rhodopsin  Break down into 2 molecules  Generate action potential o Cone pigments  Chlorolabe - green  Erythrolabe - red  Cyanolabe - blue Brightness Vision and Dark Adaptation  Rods have more brightness sensitivity than cones except red  Cones are most sensitive to greenish-yellow range  Dark Adaptation: progressive improvement in brightness sensitivity occurring over time under low illumination o After absorbing light, a photoreceptor is depleted of its pigment molecules for a period of time o During dark adaptation, photopigment molecules are regenerated and receptor’s sensitivity increases o Two part curve where you shine light  First part – dark adaptation of cones causes it to gradually become more sensitive to light  ↑ time in dark = threshold intensity decreases to an asymptote at 10 minutes  Second part – start after first part ends, rods have slower regeneration time but more sensitive  Reach max 30 mins later o Work in rooms with red light if you want better night vision  Red light stimulates cones  Rods remain in state of dark adaptation Single Retinal Ganglion Cell Recording  Maximum response – middle  Minimum response – outer ring  Every ganglion cells has a site where excites it or turns it down Recording From the Visual Cortex (Hubel and Wiesel)  Retinal ganglion cells response to spots of light  In cortex, cortical cells response to slit of light in specific orientations and motions  Simple cell e.g. straight line o Fires to a slit at a particular orientation on a specific retinal location  Complex cell e.g. parallelogram o Moving slits at particular orientation  Hypercomplex cell e.g. facial recognition o Combination of stimulus features and recognizable shapes Colour Vision  Distinguish many different colours due to small difference thresholds for light wavelengths  The Trichromatic (Young-Helmholtz) Theory o Additive colour mixture – combination of wavelengths o Cones are most sensitive to blue, green or red o Receptor sends messages to brain based on extent they are activated by light energy’s wavelength  If all 3 cones are equally activated – pure white colour o Did not fit theory  Red + green = yellow  Red green colour blindness can experience yellow  Afterimage (image in diff colour appear after a colour has been viewed steadily and withdrawn)  Opponent-process Theory by Ewald Hering o 3 types of cones respond to two different wavelengths  Red or green  Blue or yellow  Black or white o Stare at picture for a long time  Receptors to colours become fatigued  Opposite colour responded when look a white blank space (reflect wavelengths)  Dual Processes in Colour Transduction (Combine both theories) o Trichromatic – right about cone sensitivity to blue, red and green wavelengths o Opponent – do not occur at level of cones  Certain ganglion cells in retina, some neurons respond by altering rate of firing  Green light – slow firing  Red, green and blue trigger their own colour opponent process  Activity of blue-sensitive cones directly stimulates blue processes  Yellow is stimulated by red and green sensitive cones  Trichromats – normal colour vision  Colour-Deficient Vision - deficiency in red-green and/or yellow-blue system o Absence of hue-sensitive photopigment in certain cone types o Dichromat – colour blind to one system o Monochromat – black and white system Analysis and Reconstruction of Visual Scenes  Feature Detectors: fire selectively in response to stimuli that have specific characteristics  Parallel processing: overlapping modules constrict unified image of its properties  Retina  optic nerve  thalamus  primary visual cortex  visual association cortex o Fovea produces high visual acuity in large area of visual cortex o nerve impulses from rods and cones to recognizing learned interpreted by memory and knowledge Audition  sound waves (mechanical energy) are stimuli  sound – pressure of waves in medium  vibration from compression and expansion waves in air  frequency – number of sounds waves or cycles/s o 1 hertz = one cycle per second o Higher frequency = higher pitch o 20 hz – 20 000 hz  Amplitude o High amplitude = louder = higher level of decibel o Amplitude in levels of decibels (db) by 10  measure of physical pressures that occur at the eardrum Auditory Transduction: From Pressure Waves to Nerve Impulses  Sound waves travel into auditory canal to eardrum (movable membrane vibrates in response to waves)  Middle ear – tiny bones create pressure at oval window to set fluid inside cochlea into motion o the hammer (on eardrum) – malleus bone o incus – anvil shaped bone o stapes - small stirrup-shaped bone in middle ear, transmitting vibrations from incus  inner ear o vibrations of bones amplifies sound waves  Inner ear (cochlea) o coil, snail shaped tube filled with fluid o fluid waves result vibrate the basilar membrane (sheet of tissue) and membrane above it o organ of Corti – resting on basilar membrane that contains many tiny hair cells (actual sound receptors)  hair cells synapse with neurons  auditory relay station  auditory cortex in temporal lobe  causing bending of hair cells in the organ of Corti  trigger release of neurotransmitter substance into synaptic space between hair cells and neurons of auditory nerve, resulting in nerve impulses sent to brain  within auditory cortex, detector neurons respond to specific kinds of auditory input Coding of Pitch and Loudness  loud = high amplitude waves o hair cells bend more o release more neurotransmitter substance = higher rate of firing in axons of auditory nerve  coding of pitch o Low frequency below 1000 hertz = slower wave– frequency theory is true o High frequency above 1000 hertz = abrupt wave – place theory is true o Frequency Theory: pitch perception, nerve impulses sent to brain match frequency of sound wave  However, neurons are limited in rate of firing o Georg von Bekesy – Place Theory  Auditory cortex has tonal frequency “map” at specific areas of cochlea representing a pitch Sound Localization  time and intensity differences of sounds arriving at the two ears to locate the source of sounds  Binaural (two- eared) ability to localize sounds is sensitive Hea
More Less

Related notes for Psychology 1000

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.