Chapter 6 Sensation and Perception Visual and hearing most important for midterm Visual illusions why Sensation stimulation of the sense organs Pure incoming information Passive process Stimulus energy neural impulse Perception selection organization and interpretation of sensory input Active process What info is imp How Gives meaning to what we sense Brain damaged patient can sense but cannot perceive Transduction moving from sensation to perception SENSATION the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment PERCEPTION the process of organizing and interpreting sensory information enabling us to recognize meaningful objects and events Sensing the World Some basic Principles Sensation and perception one continuous process BOTTOM UP PROCESSING analysis that begins with the sensory receptors and works up to the brain s integration of sensory information Enables our sensory systems to detect the lines angles and colors that form the horses rider and surroundings painting page 180 Details whole pic Sensory receptors brain Eyes mouth nose a face TOP DOWN PROCESSING information processing guided by higher level mental processes as when we construct perceptions drawing on our experiences and expectations We consider the painting s title The Forest Has Eyes by Bev Doolittle notice the apprehensive expressions and the direct our attention to aspects of the painting that will give those observations meaning expectation changes what you perceive Experience gives meaning Stored knowledge alters our perception o Recognition eg My face friend s face Thresholds to cut out the unimportant information Evolution survival sensing change ABSOLUTE THRESHOLDS the minimum stimulation needed to detect a particular stimulus 50 of the time Very sensitive to some kinds of stimuli standing on top of a mountain on an utterly dark clear night most of us could see a candle flame a top another mountain 30 miles away Baby s cry Bee s wing falling on your cheek skin is very sensitive Some things are sensed but not perceived SUBLIMINAL STIMULATION below one s absolute threshold for conscious awareness We still perceive it Penetrate our unconscious speak to our brain directly Help lose weight stop smoking or improve our memories Masked by soothing ocean sounds unheard messages I am thin will they say influence our behavior Assumptions We can Unconsciously sense subliminal stimuli Without our awareness these stimuli have extraordinary suggestive powers Do they actually influence us o Brief effects on mood o But we don t really act on it DIFFERENCE THRESHOLDS the minimum difference between 2 stimuli required for detection 50 of the time We experience the difference threshold as a just noticeable difference jnd differs depends on the stimulus Tells when a stimuli changes Parents must detect the sound of their child s voice amid other children s voices The detectable difference increases with the size of the stimulus WEBER S LAW for their difference to be perceptible 2 stimuli must differ by a constant proportion NOT a constant amount Change blindness if its slow or subtle we may not notice it Unintentional blindness we do not perceive unimportant things information Subtle stimuli we tune out a lot of stuff do we still perceive any of it Cocktail party effect single convo in the noise Priming Activating associations in memory Memory web of associations Activating a prime recall of related material Bargh eg priming elderly stereotypes walk slowly Sensory Adaptation SENSORY ADAPTATION our diminishing sensitivity to an unchanging stimulus When you smell a bad odor you can sense it only for some time after which the odor is gone your nose no longer senses it it has adapted to it Reduces our sensitivity ve Benefit freedom to focus on informative changes in our environment without being distracted by the constant chatter of uninformative background stimulation Vision Our culture loves sight Vision truth and goodness o Good students bright o Good answers illuminating o the eyes are the windows to the soul The Stimulus Input Light Energy What strikes our eye is NOT color but pulses of energy that our visual system perceives as color color different wavelengths Visible light is a thin slice of the whole spectrum of electromagnetic energy 2 physical characteristics of light help determine our sensory experience of light Wavelength the distance from the peak of one light or sound wave to the peak of the next Intensity the amount of energy in a light or sound wave which we perceive as brightness or loudness as determined by the wave s amplitude The Eye Object Light cornea protects the eye and bends light to provide focus pupil a small adjustable opening surrounded by the iris muscle which constricts and dilates to regulate how much light enters the eye lens focuses incoming light rays into an image on the retina by changing its curvature in a process called accommodation muscle attached adjusts the lens retina multilayered tissue on the eyeball s sensitive inner surface The object is reversed on the retina fovea RETINA the light sensitive inner surface of the eye containing the receptor rods and cones plus layers of neurons that begin the processing of visual information Receptor cells rods and cones the light energy trigger chemical changes that would spark a neural impulse activating bipolar cells bipolar cells activate ganglion cells axons from the network of ganglion cells converge to form the optic nerve that carries the information to the brain RODS retinal receptors that detect black white and gray necessary for peripheral and twilight vision when cones don t respond Concentrated near the peripheral region of the retina No hotline as cones Share bipolar cells with other rods sending combined messages CONES retinal receptor cells that are concentrated near the center of the retina and function in daylight or in well lit conditions The cones detect fine detail and give rise to color sensations Cluster around the fovea the retina s are of central focus Have their own hotline to the brain certain bipolar cells relay information to the brain directly from the cones preserve the information able to detect fine detail Acuity sharpness and precise detail because they are clustered OPTIC NERVE the nerve that carries neural impulses from the eye to near the fovea the brain BLIND SPOT the point at which the optic nerve leaves the eye creating a blind spot
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