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General Psychology (PSY2200 MBAC). Chapter 05: Sensation and Perception. Sensation versus Perception. Sensation: the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
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General Psychology(PSY2200 MBAC) Chapter 05: Sensation and Perception
Sensation versus Perception • Sensation: the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment • Bottom-up processing: analysis that starts with the sensory receptors and works upward to the brain • Perception: the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events • Top-down processing: information processing guided my higher-level mental processes; bringing our experiences and expectations to bear
The Difference Between Sensation and Perception What do you see?
Top-Down Processing Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a wrod are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the word as a wlohe.
Top-Down Processing • Likelihood Principle: ”we will perceive the object that is most likely to be the cause of our sensory stimulation” (Herman von Helmholtz) • Hypothesis Testing: “we may think of sensory stimulation as providing data for hypotheses concerning the state of the external world” (Richard Gregory)
Sensation Vision as an Example
SensationVision • Cornea: Clear layer of tissue; begins focusing the image • Aqueous humor:thickened clear fluid; keeps the front of the eye firm and slightly curved • Iris: ring-shaped muscle that controls the size of the pupil (and gives the eye its color) • Pupil:the opening at the center of the iris; the entry point of light into the eye; size of the pupil determines how much light gets into the eye • Lens: stiff, jelly-like tissue that can squeeze into a tight ball or flatten out; adjust focus • Vitreous humor:clear liquid filling the body of the eye
SensationVision • Retina: sheet of tissue at the back of the eye; responsible for converting light into neural signals to be relayed to brain • Photoreceptors • Rods: very sensitive to changes in contrast; imprecise in detecting position and insensitive to color; located in periphery of the retina; responsible for “night vision” • Cones: high precision; specialized to detect red, green, or blue light; located in the Fovea (high spacial acuity) • “Preprocessing” – cells reduce and detect information regarding form and motion • Bipolar cells • Horizontal cells • Amacrine cells • Ganglion cells: receive information from eye and send threads through the retina and to the optic nerve • Optic Nerve: takes data from eye through the thalamus and to brainstem and a region of the occipital lobe called the primary visual cortex or striate cortex • Thalamus: sensory relay station; more preprocessing
Vision The Case of Blindsight
Perception What We Make of It
Vision and Perception Pulsing
Vision and Perception Spinning
Exercise Vignettes (Handout 5-17)
Bias Effect • In the Spring of 2002, 90% of Americans said groups of Arabs carried out the attacks on 9/11, huge majorities in Islamic countries said this was not true • 89% in Kuwait • 86% in Pakistan • 59% in Iran • 63% of Americans said military action in Afghanistan was totally justified compared with less than 10% in most Muslim countries • 1 in 4 Americans have a favorable view of Muslim countries; 1 in 4 residents in Islamic countries had a favorable view of the US • 2 in 3 Americans say Muslim countries would be better off if they adopted Western values; fewer than 1 in 3 citizens of the Muslim world agree Bernedetto, R. (2002, March 5). Differences in perceptions fuel mistrust. USA Today, p. 11A.
Bias EffectContinued • Pew Research Foundation polled 16,000 people in 20 nations and the Palestinian Authority regarding their perceptions • Favorable opinion of the United States: • Israel: 79% • Australia: 60% • France: 43% • Lebanon: 27% • Jordan: 1% • Palestinian Authority: 0% • Without Saddam Hussein in power, the Iraqi people will be better off: • United States: 87% • Canada: 81% • Kuwait: 80% • Without Saddam Hussein in power, the Iraqi people will be worse off: • Palestinian Authority: 85% • Jordan: 80% • Indonesia: 67%