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Sensation vs Perception • What’ What’s the difference? Psychology 101 Sensation Sensation vs Perception • Sensation – What comes into our body through our sensory organs How do we construct our environment? • We construct it • Our systems can be tricked! • Perception – What our brain does with that information MullerMuller-Lyer Titchener’ Titchener’s circles 1 Red spirals Look at the greys Kanisza’ Kanisza’s triangle An introduction to the Gestalt principles How can we study our senses? • What can we do to understand how visual information is processed? – Sounds? – Smells? • How could we study this in psychology? 2 Psychophysics Psychophysics: The point • The main idea • We notice some incoming information and • To learn about our senses by pushing don’ don’t process others • Absolute thresholds • Example: the auditory system – Minimum threshold to detect something 50% of the time Signal Detection Theory them to the limits – Play a sound very quietly – Eventually it’ it’ll be so quiet, you may not be able to hear it – Absolute threshold: the loudness that people say they can hear the sound 50% of the time Other things: Subliminal Stimulation • Stimulating our consciousness • Priming studies – Changing opinions by showing something subliminally – Ch_ _ _ Just Noticeable Difference Just Noticeable Difference • Weber’ Weber’s law – Difference thresholds are not constant, but proportional – Start with a 1lb book • May notice a .1 lb change – Now start with a 1000 lb desk • Will you notice a .1 lb change? 3 Sensory adaptation What about vision? • Do you feel your clothes if they are still? • How about hearing a sound that hums in • What about a line that is in one place in the background consistently? Two ways to processing the world • BottomBottom-up processing: – Our sensory systems experience the world and send the information upwards to the brain • Eg. Eg. watching a movie your field of vision? – Why is this different? – Eyes are constantly moving • Saccades Vision: The beginning • What do we see? – Light is waves • TopTop-down processing – How our minds interpret what our senses detect (ie (ie.. seeing, hearing) • Eg. Eg. Don’ Don’t look behind the door The visual spectrum Vision • We can only see a small portion of the • The Eyeball • Light shines through waves of visual light the cornea • Becomes inverted on the retina 4 Parts of the eyeball The Retina: The most important part • Cornea: outermost part • Contains rods and cones • Rods: nighttime use – Protects the eye • Pupil and Iris – Allow light to enter • Lens – Focus light on retina • Retina – Back of eyeball where light is processed Rods and Cones – insensitive to color – located in retinal periphery – When you step into a movie theatre, it takes a while to see because your rods are kicking in. • Cones: 3 types of light sensitivity (red, green, blue) – essential for color perception – daytime use – primarily in center of retina • better acuity What do rods and cones do? • They are sensitive to different wavelengths • Transduction – Turns light into something our nervous system can use • Electrical signal – Rods and Cones do this specifically for their type (color) of light What about problems seeing? How the visual system works • Nearsightedness: image focused too soon • Farsightedness: image focused too far 5 Stages to visual processing Color vision • Visual perception occurs in stages • One are may process color • Another may process depth or form • YoungYoung-Helmholtz theory – Trichromacy – Found in the retina • Opponent process theory – RedRed-green, blueblue-yellow, and blackblack-white – Input from one color inhibits the other color YoungYoung-Helmholtz Theory Opponent Process Theory Hearing • Sounds are waves • Amplitude / Height = loudness • Frequency = pitch 6 The Ear Typical Sounds • Outer ear – Ends at ear drum • Middle ear – Composed of bones • Inner ear – Cochlea – Fluid filled – Hairs • Transduction How we hear Getting to the Brain • Sound waves get to • Different parts of the auditory cortex • • • the cochlea Ripples in fluid Hair cells sway with the ripples Different frequencies of sound move the hair cells that are in different parts of the cochlea process the different frequencies of sound Higher frequencies processed in the yellow region Lower frequencies processed in the blue region Sound Location Processing Touch processing • How can we tell where a sound is coming • Multiple somatosensory from? – Difference in loudness between the two ears • Interaural Intensity Difference – Difference in time of arrival for the sound waves between the two ears • Interaural Time Difference subsystems – Touch • Pressure, vibration • Temperature • Pain – Joint position – Muscle stretch 7 Organization in the Brain Taste Taste buds: sensory receptors Taste Sensations sweet sour salty bitter Sensory Interaction the principle that one sense may influence another as when the smell of food influences its taste The Tongue 8