Ch. 5 notes

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University of Toronto Scarborough
Steve Joordens

-Somatosenses (body senses): dendrites of Ch. 5 Sensation neurons respond directly to physical stimuli (no - learning: detection by sensory organs nerves receptor cells) brain - sensory organs and nerves: provide us w. Useful SENSORY CODING (codes by which brain info of external world - differences bw sourcesof info in evn = transmits info) Anatomical coding: (location, type of stimulus, important consequences for the way the sensory system prcessesthat info activation of specific nerve fibre of other) - Johannes Muller: doctrine of specific Ex. seeing(rapid scene changes) vs. Hearing (gradual changes as we move) the world. energies - Diff sensory organs send messages to dif places in the brain Sensory processing - The way the nervous system represents Sensation: detection of simple properties of information stimuli (brightness, colour, warmth, sweetness) - Ex. rubbing eye... light receptors Perception: activations... action potentials... see - detection of objects (animate, inamiate), starts... their - Therefore, sensory coding for the body - location of objects surface is anatomical - movements of objects - Tells where the body is being touched - backgrounds of objects Temporal coding: (richness in messages due to Before: psychologists... belief: perception pattern of firing) depended on learning, sensation inate - A way by which the nervous system codes physiological mechanism information in terms of time - Simple sensations no boundry established - Simple form of temporal code: time... still complex perceptions rate... light touch = low firing... - Tells the intensity of touch through the TRANSDUCTION*(highlight of chapter) rate of firing Brain: cerebrospinal fluid, meninges sheaths, thick skull, has: only some receptors: detect PSYCHOPHYSICS temperature, salt [] of blood Psychodynamics: (physics of the mind) 1. Sense organs located outside the brain gather measure of quantitative relation bw physical info from the external world, through stimuli: stimuli and perceptual experience light, sound, taste, touch The principle of just noticeable difference: 2. Neural impulses (axon potentials) transmit information of stimuli to brain (Ernest Weber) - How do humans discriminate bw dif Transduction: process: sense organs convert energy from the environmental events neural stimuli? - Measured: jnd (smallest change in activity magnitude of a stimulus that a person can Receptor cells: release neurotransmitters that detect) stimulate other neurons alter rate of firing of - Discovery of principle: jnd is directly axons related to magnitude of stimulus - Presented 2 lights... Made one brighter - a mathematical theory of the detection of slowly... you tell him to tell you when he stimuli, which involves discriminating a signal notices the difference in light from the noise in which it is imbedded - Jnd is the magnitude of the first point at - measuring the sensitivity of cognitive system by which he notices the difference... 0... minimizing bias 0.01.... 0.02.... 1=dif noticed=jnd Ex. Sitting in quite room. Flash of light followed - Waber fractions: ratio bw jnd and the by pop (maybe) - light followed by pop... yes... yes... yes.... magnitude of a stimulus (140...) - Ex. start at 40... 40.1.... 4.5... 41 difference - overtime... pop gets lighter... hard to detect. noticed!... 400... 401... 402... 403... 410 differencenoticed! -yes no is biased - hits = correct yes when pop is present Conclusion (reading graph): -when looking at a brighter light, you - miss =incorrect no when pop is present need more of a difference to seea difference - correct negative = correct no when pop - Dim light needs less of a difference to not present seea But amount more is constant. - false alarms = incorrect yes when no - Internal event was reliably measured!... pop is present mind can now be studied. - blind, cant perceive anything: hit rate = false Signal detection theory: (alternative method alarm rate to measure a persons sensitivity to signals - not blind folded: hit rate > false alarm rate regardless of bias... minimize bias) - false alarm rate is never higher unless some1 is Threshold: line bw not perceiving and being silly perceiving - a persons response bias seriously affects an Absolute threshold: min value of stimulus that investigators estimate of the threshold of can be detected detection Difference threshold: min detectable diff bw 2 - person with a response bias to avoid false stimuli (jnd) alarm may show a higher sensitivity ... Subliminal perception: point where its a little Solution: set intermediate conditions below the point where person does not process it - Ex. $1 for every hits, -$0.50 for misses but it is in there somewhere.... (used in Receiver operating characteristics curve marketing) (ROC CURVE): Curve: shows performance - psychologists realized: threshold was not a fixed when sound difficult to detect value - The concept of threshold is not used in this - some participants may seesomething that method others dont - Person decides wether a stimulus occurred Convention: threshold = detection 50% of the - Above horizontal line = null sensitivity... - hit rate > false alarm... person is time - activity of the nervous system is variable (non actually percieving stimuli avtivation or no activation for very dim signals) - Theory emphasises: sensory experience involves factors other than the activity of the sensory Jastrows (1897): subliminal perception card experiment systems (motivation and prior experience) Signal Detection theory: contd
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