Sensation and Perception Chapter 5

1. Sensation and PerceptionChapter 5

2. Sensation and Perception Perceptual Organization • Form Perception • Depth Perception • Perceptual Constancy Perceptual Interpretation • Sensory Deprivation and Restored Vision • Perceptual Adaptation • Perceptual Set Definitions Sensing the World: • Thresholds • Sensory Adaptation Vision • The Stimulus Input: Light Energy • The Eye • Visual Information Processing • Color Vision

3. FINISHED FLIES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCES OF YEARS

4. Sensation & Perception How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we select, organize, and interpret our sensations, the process is called perception.

5. Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

6. Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT

7. Making Sense of Complexity Our sensory and perceptual processes work together to help us sort out complex images. “The Forest Has Eyes,” Bev Doolittle

8. Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them.

9. Exploring the Senses What stimuli cross our threshold for conscious awareness?

10. Proportion of “Yes” Responses 0.00 0.50 1.00 0 5 10 15 20 25 Stimulus Intensity (lumens) Thresholds Absolute Threshold:Minimum stimulation needed to detect a particular stimulus 50% of the time.

11. Absolute threshold The smallest intensity of a stimulus that must be present for it to be detected Sensing the World Around Us

12. Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock

13. Puzzles of Perception • Can we ever perceive what is happening below our usual sensory threshold? • Can we pick up signals from world or from other people without using our usual sensory channels at all?

14. 6 Perceiving without Awareness Priming A method used to insure unconscious processes, in which a person is exposed to information and is later tested to see whether the information affects behavior or performance on another task or in another situation Findings suggest simple primes influence perception, memory, thinking, and decision-making.

15. 6 Perception vs. persuasion Although subliminal priming can influence judgments and preferences, research doesn’t support its success in major levels of persuasion.

16. 6 Extrasensory perception ESP The ability to perceive something without ordinary sensory information Has not been scientifically demonstrated

17. 6 Difference threshold The smallest difference in stimulation that can be reliably detected by an observer when two stimuli are compared Also called the Just Noticeable Difference (JND) Also known as Weber’s Law

18. Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it.

19. Vision

20. Transduction In sensation, the transformation of stimulus energy (sights, sounds, smells) into neural impulses.

21. The Stimulus Input: Light Energy Visible Spectrum Both Photos: Thomas Eisner

22. Physical Characteristics of Light • Wavelength (hue/color) • Intensity (brightness)

23. Wavelength (Hue) Violet Green Orange Red Indigo Blue Yellow 400 nm 700 nm Long wavelengths Short wavelengths Different wavelengths of light result in different colors.

24. Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more “washed out” or “darkened.”

25. The Eye

26. Parts of the eye • Cornea: Transparent tissue where light enters the eye. • Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. • Lens: Focuses the light rays on the retina. • Retina: Contains sensory receptors that process visual information and sends it to the brain.

27. The Lens Lens:Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

28. Retina Retina: The light-sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual information.

29. Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster. http://www.bergen.org

30. Photoreceptors E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

31. Visual Information Processing Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.

32. Feature Detection Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. Ross Kinnaird/ Allsport/ Getty Images

33. Shape Detection Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses. Ishai, Ungerleider, Martin and Haxby/ NIMH

34. 6 Trichromatic theory Young (1802) and von Helmholtz (1852) both proposed that the eye detects 3 primary colors Red, blue, and green All other colors derived by combination

35. Color Blindness Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory. Ishihara Test

36. 6 Afterimages