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Oct 1st - John Logan

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Carleton University
PSYC 1001
John Logan

Psychology Oct 1st 2013 Sensation Vs. Perception • Sensation • Sensory Receptors • Transduction - results of info in environment, and transferred into action potentials • Perception • Interpretation of sensory information based, in part, on previous experiences. (i.e. listening to someone speak a foreign language. You can hear the sound, but it does not register as words) • Discriminate Among The Senses • sensory receptors are specialized to absorb a particular type of energy. • sensory receptors have different neural pathways • loss of sensory channel often results in enhanced sensory skills in another area •blind people are more accurate at locating a sound source and are more sensitive to touch. • Perception • Brain automatically perceives the information it receives from the sense organs (reading) • bottom-up processing vs. top-down processing. •bottom-up: sensory processing •top-down: interpretation • Psychophysics link between physical properties of stimuli and a person’s experience of stimuli • (sensation -> perception) • sensation begins with a detectable stimulus • Gustave Fechner: the concept of the threshold •Absolute Threshold - lower limit for detecting presence of stimulus •Absolute Thresholds aren’t really absolute •The probability of detecting a stimulus increase gradually with stimulus intensity, as shown in red; an “absolute” threshold is defined as the intensity level at which the probability of detection is 50%. •Examples: • Candle flame at 30 miles on a dark clear night • Hearing a ticking watch at 20 feet under quiet conditions Psychology Oct 1st 2013 •Smell one drop of perfume diffused through-out three rooms •Taste a teaspoon of sugar in 2 gallons of water •Touch the wing of a fly falling on your cheek from a distance of one centimeter • Environment is seldom ideal •Noise (Any extra stimulus) is an irrelevant and competing stimulus • Individuals have different absolute thresholds Subliminal Perception • • Individuals can detect information that is below the lebel of conscious awareness • Fowler et al. (1981) • presented words subliminally (e.g. lodge) • asked which of two words was most like subliminal word (e.g. hotel or book) • results: usually picked correct word. • There is no evidence subliminal perception affects conscious thoughts and behaviour • Difference Thresholds • Just Noticeable Difference (JND) • smallest difference in stimulation required to discriminate one stimulus from another 50% of the time • Weber’s Law Two stimuli must differ by a constant proportion for the difference to be • detected. (e.g. 100lbs weight compared to another weight must be 10lbs or up and constant to get accurate detection) •proportion varies with type of stimulus • Signal Detection Theory • Detection of a stimulus depends on a variety of factors besides the physical intensity of the stimulus and the sensory abilities of the observer • fatigue, expectancy and urgency affect detection. • Vision • Light = Electromagnetic Radiation • wavelength: perception of colour • amplitude: perception of bri
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