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Psychology - Sensation & Perception.docx

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PSYC 2510
Richard N Lalonde

October 3, 2012 Psychology - Lecture #5 Sensation and Perception Definitions:  Sensation: process where a stimulus excites a receptor which changes info. into a neural message  Perception: selection, organization and interpretation of a sensory experience  Sensation – physical experience  Perception – cortical integration Steps in sensation:  Stimulus (physical energy)  Accessory structures: o Sense receptors- transduction o Conversion of physical energy into neural activity  Coding: translating physical properties into patterns of neural activity Sensation and Perception Processes Sensation – Specific Nerve Energies  Different sensory systems – signals received by sense organs stimulate different nerve pathways to different areas of the brain  Synesthesia o Stimulation of one sense evokes another  Graphic syn. – letters/numbers perceived as inherently coloured  Nabokov complained to his mother: red ‘A’ block should be blue – he sensed the letter “A” to be blue  Can see numbers and letters in terms of colour and sounds Senses  Audition (hearing)  Taste  Vision  Touch  Smell  Movement (kinesthetic & vestibular systems) Hearing  Energy: sounds waves  Accessory structures: from pinna (outer ear) to cochlea (inner ear) & organ of Corti  Transduction: hair cells (cilia) on basilar membrane (cochlea floor) bend as fluid movies – signal to auditory nerve  Coding of waves: o Amplitude = loudness (decibels) o Length (frequency) = pitch (hertz) o Purity = timbre (flute to oboe) Taste (gustation)  Energy: food  Accessory structures: papillae (taste buds)  Transduction: cells in taste buds (10,000)  Coding: o Salty o Sour o Bitter o Sweet o Umami – savoury Taste Perception  People have different tastes (interpretation) o Genetics (sensation level) o Culture o Learning o Food attractiveness Sensation in Vision  Energy: light waves  Accessory structures: parts of the eye  Transduction: photoreceptors (rods and cones) – rods for black & white, cones for colour  Coding of light waves: o Length = colour (hue)  Red is long o Amplitude = brightness o Purity = saturation  Pure (one length) to unsaturated (white) Parts of the eye:  Cornea – protects interior & bends light  Pupil – opening in iris; controls amount of light  Lens – focuses light (flat-far & round – near); called the process of accommodation – ciliary muscles  Retina – point of transduction o Rods: (100-125 million) black and white photoreceptors periphery o Cones: (5-6 million) RGB concentrated in fovea o Receptive field – collection of rods and cones that funnel signals to a ganglion cell o Optic disk (blind spot) – rods and cones exiting the eye form the optic nerve Connections in Vision  Main pathway: photoreceptors (rods & cones) – bipolar cells – ganglion cells – axons of gang. Form optic nerve – optic chiasm (point of cros-over) – LGN lateral geniculate nucleus (thalamus) – primary visual cortex (occipital lobe)  Mnemonic – Take a photo of the bipolar gang who have the nerve to opt for chi tea across the street where they genuflect to get a prime view of the ocspital. The Structures of the Retina Theories of colour vision 1. Young-Helmholtz trichromatic theory  3 types of cones (R, G & B) & all colours are combos of these  “colour deficient” – cannot distinguish between red & green (Colour blind)  Problem: negative afterimage (what was white in original image shows up black after) 2. Hering’s opponent-process theory  3 opposing systems (red vs. green; blue vs. yellow; black vs. white)  Pairs inhibit each other  Negative afterimage – lateral antagonism – intense neural activity in a cell opposes activity in surrounding cells (when one set stops firing, the other starts and vice versa) Both theories have support  Tricromatic works at the level of cones  Opponent process theory at the level of ganglion cells (as well as
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