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Sensation vs. Perception

Sensation vs. Perception. Sensation: a process by which our sensory receptors and nervous system receive and represent stimulus energy Sensation is the raw data our brain takes in from the environment. Sensation vs. Perception.

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Sensation vs. Perception

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  1. Sensation vs. Perception • Sensation: a process by which our sensory receptors and nervous system receive and represent stimulus energy • Sensation is the raw data our brain takes in from the environment.

  2. Sensation vs. Perception • Perception: a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. • Perception “makes sense” of sensation. • Both involve one continuous process and perceptual failure may occur at any level whether at the sensory level or the perceptual interpretation level. • Example:Prosopagnosia

  3. Bottom Up vs. Top Down Processing • Bottom Up Processing: analysis that begins with the sense receptors and works up to the brain’s integration of sensory information. • Involves making sense of raw sensation. • Top Down Processing: Information processing guided by higher-level mental processes • As when we construct perceptions drawing on our experience and expectations. • Our expectations and experiences shape how we perceive information.

  4. Prosopagnosia • Is a condition…

  5. Bottom Up vs. Top Down

  6. Bottom Up Vs. Top Down • What do you see?

  7. Bottom Up vs. Top DownOLD WITCH IN PICTURE

  8. Psychophysics • Psychophysics: study of the relationship between physical characteristics of stimuli and our psychological experience of them • Light- brightness • Sound- volume • Pressure- weight • Taste- sweetness

  9. Sensation: Thresholds • Absolute Threshold: minimum stimulation needed to detect a particular stimulus. • Usually defined as the stimulus needed for detection 50% of the time.

  10. “Subliminal Messages” • What does the research say? • http://jeffmilner.com/backmasking.htm • http://www.nlpweekly.com/?p=527 • Homework

  11. Sensation: Thresholds • Difference Threshold or (JND-Just Noticeable Difference): the minimum difference that a person can detect between two stimuli. What does it take to tell two similar stimuli apart? • Weber’s Law: to perceive a difference between two stimuli, they must differ by a constant proportion • light intensity- 8% • weight- 2% • tone frequency- 0.3%

  12. Sensation: Thresholds • Signal Detection Theory:predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) • Assumes that there is no single absolute threshold • What might a person’s detection of a stimulus depend on?

  13. Sensory Adaptation • Sensory Adaptation: diminished sensitivity with constant stimulation. • Ocean • Bad Smell • Ads- cut in, zoom, fade out

  14. Sensory Adaptation and Vision

  15. The Science of Energy and Sensation • Transduction- conversion of one form of energy to another. • Wavelength- the distance from the peak of one wave to the peak of the next. • Hue- dimension of color determined by wavelength of light…color is matter of how far wavelengths are apart. • Intensity- amount of energy in a wave determined by amplitude. • brightness • loudness

  16. Human Vision Represents Narrow Part of All Electromagnetic Energy ROY G. BIV: Starts from longer to shorter wavelengths. R=longest; V=shortest

  17. Great amplitude (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision: Physical Property of Waves

  18. Biology of Vision Step One: Light Enters the Eye 1.) Light enters the eye through the cornea: (transparent protector) and the light passes through the pupil: (small opening/hole). The size of the opening (pupil) is regulated by the iris: the colored portion of your eye that is a muscular tissue which widens or constricts the pupil causing either more or less light to get in.

  19. Biology of Vision Step Two: An Image is Produced 2.) Behind the pupil, the lens, a transparent structure, changes its curvature in a process called accomodation,and focuses the light rays into an image on the light-sensitive back surface called the retina: where image is focuses.

  20. Biology of Vision Step Three: Chemical Reactions and Sight 3.) Image coming through activates photoreceptors in the retina called rods and cones. As rods and cones set off chemical reactions they form a synapse with bipolar cells which forms a synapse with ganglion cellswhich fire action potentials along the optic nerve: that carries this information to be processed by the Thalamus: (sensory switchboard)that sends information to the visual cortex which resides in the occipital lobe. The brain then constructs what you are seeing and turns image right side up.

  21. Parts of Retina • Blind Spot:part of retina where optic nerve leaves the eye…no receptor cells are there. Brain fills information in with info from other eye. • Fovea:central focal point of the retina, where cones cluster. • Cones: located near center of retina (fovea) • fine detail and color vision • daylight or well-lit conditions • Rods: located near peripheral retina • detect black, white and gray • twilight or low light

  22. Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No Rods & Cones

  23. Errors In Vision • Acuity: the sharpness of vision • Nearsightedness: • nearby objects seen more clearly • lens focuses image of distant objects in front of retina • Farsightedness: • faraway objects seen more clearly • lens focuses near objects behind retina

  24. Errors in Vision • Normal Nearsighted Farsighted Vision Vision Vision

  25. Visual Involves Parallel Processing • Parallel vs. Serial:parallel means simultaneous while serial means step by step. Our brains process are often parallel processes while computers work serially. • Parallel Processing: simultaneous processing of several dimensions through multiple pathways. Different part of brain for: • color • motion • form • depth

  26. Parallel Processing • Feature Detectors: neurons in the visual cortex respond to specific features • shape • angle • movement

  27. How The Brain Perceives

  28. Visual Information Processing • Trichromatic (three color) Theory • Young and Helmholtz • three different retinal color receptors • red • green • blue

  29. Color Deficient Syndrome People who suffer red-green blindness have trouble perceiving the number within the design

  30. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision. Example: Jesus On Title Slide. “ON” “OFF” redgreen green red blue yellow yellowblue black white white black

  31. Stare At This for 30 Seconds Then Look At A White Surface

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