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Chapter 3: Sensation & Perception We understand world thru our senses, our “windows” on the world Our reality= dependent upon 2 basic processes: oSensation: gathering info & recording by sensory structures ; mechanical process oPerception: interpreting info; interpretation of sensory info by the brain ; active process Perception does not offer an exact replica of the world outsidebrain subjectively constructs the world using innate & learned assumptions & principlesDetectionQuestion: concerned w/ the limits on our ability to detect very faint signals How intense does a light have to be for us to see it? How intense does a sound have to be for us to hear it?oAbsolute threshold: minimum amt of energy in a sensory stimulus that’s detected 50% of the timeoSubliminal stimulus: stimulus that’s detected only up to 49% of the time Any effects of subliminal persuasion = short-lived w/ no long-term consequences onour behavioroSignal detection theory: detection of faint sensory stimuli depends upon person’s physiologicalsensitivity to a stimulus AND upon decision criterion for detection, which is based onnonsensory factors DifferenceQuestion:concerned w/ limits on our detection abilities; our ability to detect very small differences b/w stimuliWhat is the smallest difference in brightness b/w two lights that we can see? What is the smallest difference in loudness b/w two sounds that we can hear? odifference threshold(just noticeable difference(jnd)): minimum difference b/w 2 stimuli that’s detected 50% of the timeoWeber’s Law: for each type of sensory judgment, the difference threshold = a constant fraction of the standard stimulus value used to measure itScaling Question: concerned w/ how we perceive magnitudes (intensities) of clearly detectable stimuli What is the relationship b/w the actual physical intensities of stimuli & our psychological perceptions of these intensities? oSteven’s Power Law: perceived magnitude of a stimulus = equal to its actual physical intensity raised to a constant power for each type of judgmentto perceive a light as twice as bright, its actual intensity has to be increased between and 8 and 9 timesif an electric shock is doubled in intensity, we perceive it as being about 10 times more intenseoSensory adaptation: disappearance to repetitive or unchanging stimuliSurvival value—its more imp to detect new stimuli (can signal danger) than constant stimuliHue: color experienced Wavelength: distance in 1 cycle of a wave, from 1 crest to next ohuman can see wavelengths of ~400- 700 nanometersAmplitude: amt of energy in a wave (its intensity) which is the height of wave @ its crest; determines its brightnessosmall amplitude= soft sounds: dull colors ogreat amplitude= loud sounds ; bright colors osound waves loudness= amplitude expressed in decibels (dB) frequency