Sensation and Perception 9-22-10

Sensation and Perception 9-22-10 - Sensation and Perception...

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Unformatted text preview: Sensation and Perception • Sensation: stimulus detection process where our sense organs respond to and translate stimuli into nerve impulses sent to the brain. • Perception: active process of organizing stimulus input and giving it meaning (is something sad? Happy?) • Stimulus Detection: How intense does a stimulus need to be for us to recognize its presence? – Defining what them measure you are going to use to distinguish a phenomenon • Absolute Threshold: the lowest intensity at which a stimulus can be detected at least 50 percent of the time Absolute Threshold Sense Modality Absolute Threshold vision candle flame @ 30 miles on a clear night hearing watch ticking @ 20 feet in a quiet room taste 1 tsp sugar in 2 gallons of H20 smell 1 drop of perfume in 6(3) room apt touch wing of bee on cheek dropped from 1 cm • Signal Detection Theory: various factors influence our sensory judgment; often involves a process of decisions in addition to sensation – Because you watched a scary movie, you find yourself listening to things and focusing on the door screeching – Right after 9/11 plane was flying you hear it • Difference Threshold: the smallest difference between two stimuli that people can perceive 50 percent of the time-- is the sand paper rough or extra rough • Weber’s Law: the difference threshold is directly proportional to the magnitude of the stimulus to which the comparison is being made. – Eg. Value for weight is 1/50 – Backpack example (if your backpack weighs 50 pounds and you put a small book in it you probably wont feel it. PROPORTION Fechner’s Law: larger and larger increases in physical energy are required to produce equal increases in perception-eg. Light bulb example. - you have to burn a lot of popcorm to make the smell • Just noticeable difference: the smallest difference in which you can detect a difference threshold • Sensory adaptation (habituation): over time neurons decrease activity in response to a constant stimulus – Like watching TV Sensory Systems: Vision • The normal stimulus for vision is electromagnetic energy or light waves • Light waves are measured in nanometers • Our visual system is sensitive to wavelengths extending from ~700 nanometers (red) to ~ 400 nanometers (blue-violet) • ROY G BIV: (higher to lower wave lengths) The Human Eye • Light waves enter the eye through the cornea • The pupil: behind the cornea, the pupil adjusts to control the amount of light that enters the eye • The iris: the pupil’s size is controlled by muscles in the colored iris that surrounds that pupil •...
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This note was uploaded on 02/02/2011 for the course PSYCH psych 111 taught by Professor Shellyschreier during the Fall '10 term at University of Michigan.

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Sensation and Perception 9-22-10 - Sensation and Perception...

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