Myers’ PSYCHOLOGY (6th Ed)

1. Myers’ PSYCHOLOGY (6th Ed) Chapter 5 Sensation Introduction and the Eye James A. McCubbin, PhD Clemson University Worth Publishers

2. Fact vs. Falsehood • 1. On a clear, dark night we can see a candle flame 30 miles away. • 2. Advertisers are able to shape our buying habits through subliminal messages. • 3. Constant eye movement prevents our vision from being seriously disrupted. • 4. The retina of the eye is actually a piece of the brain that migrates to the eye during early fetal development. • 5. If we stared at a green square for a while and then look at a white sheet of paper, we see red. • 6. People who live in noisy environments are more likely to suffer from high blood pressure, anxiety, and feelings of helplessness. • 7. Blind musician are more likely than sighted ones to develop perfect pitch. • 8. Touching adjacent cold and pressure spots triggers a sense of wetness. • 9. People who are born without the ability to feel pain usually die by early adulthood. • 10. Without their smell, a cup of coffee may be hard to distinguish from a glass of red wine.

3. Sensation • a process by which our sensory receptors and nervous system receive and represent stimulus energy (information from our environment) • Perception • a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events (what we do with the sensory information we receive)

4. Our sensory and perceptual processes work together to help us sort out complex processes

5. How do we get information? • Bottom-Up Processing • analysis that begins with the sense receptors and works up to the brain’s integration of sensory information (body to brain) • Top-Down Processing • information processing guided by higher-level mental processes • as when we construct perceptions drawing on our experience and expectations (brain to body)

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

7. Thresholds • Absolute Threshold • minimum stimulation needed to detect a particular stimulus 50% of the time • vision: candle flame at 30 miles on a clear dark night • Hearing: the ticking of a watch 20 ft away • Sense: a bee’s wing falling 1 cm onto our cheek • Smell: a drop of perfume in a 3 room apartment • Taste: 1 tsp of sugar in 2 gall of water • Difference Threshold • minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND)

8. 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 • detection depends partly on person’s • experience • expectations • motivation • level of fatigue

9. 100 Percentage of correct detections 75 50 Subliminal stimuli 25 0 Low Absolute threshold Medium Intensity of stimulus Thresholds • Subliminal • When stimuli are below one’s absolute threshold for conscious awareness

10. Thresholds • Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage • light intensity- 8% • weight- 2% • tone frequency- 0.3% • Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

11. Eye Movement

12. How does Vision work? • Transduction • conversion of one form of energy to another • in sensation, transforming of stimulus energies into neural impulses • Wavelength • the distance from the peak of one wave to the peak of the next

13. What color is it? • Hue • dimension of color determined by wavelength of light • Intensity • amount of energy in a wave determined by amplitude • brightness • loudness

14. The spectrum of electromagnetic energy

15. 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) Physical Properties of Waves

16. Physiology of the Eye • Pupil- adjustable opening in the center of the eye • Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening • Lens- transparent structure behind pupil that changes shape to focus images on the retina

17. Eye Anatomy

18. How Vision works • Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina • Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

19. Vision problems • Acuity- the sharpness of vision • Nearsightedness (myopia)- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina • Farsightedness (presbyopia)- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

20. Vision • Normal Nearsighted Farsighted Vision Vision Vision

21. Retina’s Reaction to Light- Receptors • Rods • peripheral retina • detect black, white and gray • twilight or low light • Cones • near center of retina • fine detail and color vision • daylight or well-lit conditions

22. Retina’s Reaction to Light • Optic nerve- nerve that carries neural impulses from the eye to the brain • Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there • Fovea- central point in the retina, around which the eye’s cones cluster

24. 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 Vision- Receptors

25. Pathways from the Eyes to the Visual Cortex

26. Illusory Contours

27. Visual Information Processing • Parallel Processing • simultaneous processing of several aspects of a problem simultaneously

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

30. Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design • http://www.colblindor.com/coblis-color-blindness-simulator/

31. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” redgreen greenred blueyellow yellowblue black white white black

32. Opponent Process- Afterimage Effect

33. Visual Information Processing • Color Constancy • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object