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Chapter 4

Psychology Chapter 4.docx

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Dax Urbszat

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Psychology Chapter 4: Sensation and Perception Vestibular system  Organs in the inner ear Ian Howard  Involved in space research  Known internationally as a pioneer in sensation and perception research Three types of cues to determine which way is up  Visual  Gravity  Body direction Sensation  Stimulation of our sense organs  Involves the absorption of energy , such as light or sound waves, by sensory organs such as ears and eyes Perception  Is the selection , organization and interpretation of sensory input  Involves organizing and translating sensory input into something meaningful (ex. Your best friends face)  Begins with a stimulus  Stimulus - any detectable input from the environment  What counts as detectable depends on who or what is doing the detecting Psychophysics  Sensation and perception  Study of how physical stimuli and translated into psychological experience  Gustav Fechner o Important contributor to psychophysics o Published a seminal work on the subject in 1860 Threshold  Is a dividing point between energy levels that do and do not have a detectable effect Absolute threshold  For specific type of sensory input is the minimum amount of stimulation that an organism can detect  Define the boundaries of an organisms sensory capabilities JND  Just Noticeable Difference  Smallest difference in the amount of stimulation that a specific sense can detect  Vary by sense  The smallest detectable difference is a fairly stable proportion of the size of the original stimulus Ernst Weber  Weber’s law - states that size of JND is a constant proportion of the size of the initial stimulus  The constant proportion is called weber fraction  Not only applies to weight perception but all of the senses  Different fractions apply to different types of sensory input Fechner’s Law  Which states that the magnitude of a sensory experience is proportional to the number of JND’s that the stimulus causing the experience is above the absolute threshold  an important ramification of this law – constant increments in stimulus intensity produce smaller and smaller increases in the perceived magnitude of sensation Signal Detection Theory  proposes that detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity  Attempts to account for the influence of decision making processes on stimulus detection Subliminal Perception  The registration of sensory input without conscious awareness  Subliminal (below threshold )  Effects are relatively weak and of little or no practical concern Sensory adaptation  Is a gradual decline in the sensitivity due to prolonged stimulation  Ex. Jumping into a cold water pool and eventually becoming adapted to it  Keeps people tuned in to the changes rather than the constants in their sensory input  Most likely a behavioral adaptation that has been sculptured by natural selection The stimulus: Light  Light: o form of electromagnetic radiation that travels as a wave, moving at the speed of light o varies in wavelength (distance between peeks) and amplitude (height) o wavelength affects perception of brightness o amplitude affects perception of color The Eye:  Two main purposes o Channel light to the neural tissue that receives it called the retina o House that neural tissue  Cornea: o Light enters from here  Lens o Transparent eye structure that focuses light on falling on the retina o Accommodation: lens adjusts to visual focus  Close object: lens gets fatter  Far object: lens become flatter  Pupil o Opening in the center of the iris that helps regulate the amount of light passing into the rear chamber of the eye o Constricts: letting less light into the eye but sharpens the image o Dilates (opens): lets in more light but the image is less sharp  Retina o Neural tissue lining inside the back of the surface of the eye o Absorbs light, processes images and sends visual information to the brain  Optic Disk o A hole in the retina where the optic nerve fibers exit the eye o AKA: blind spot o Two types of receptors  Cones • At the center of the retina • Sensitive to fine detail and color (daylight and color vision) o S – blue o M – green o L - red  Rods • At the peripheral of the retina • Sensitive to color but not fine detail (night and peripheral vision)  Receptor field o Of a visual cell is the retinal area, when stimulated, affects the firing of that cell  Lateral antagonism o Occu
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