Understanding Sensation and Perception: An Exploration of Our Cognitive Processes

1. + Chapter 5 Sensation James A. McCubbin, PhD Clemson University Worth Publishers

2. Sensation • Sensation • a process by which our sensory receptors and nervous system receive and represent stimulus energy • Perception • a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

3. Sensation and Perception Paris in the the spring

4. Sensation and Perception • SenseInputPerception • Sight colors/shapes object/event • Hearing sound/noise words/music • Touch pressure/temp feel of object • Taste sour/salty/bitter/sweet flavor • Smell spicy/resinous/burned odor • rotten/fruity/flowery

5. Perception • Physiological variables: • Receptors available • Receptor limits • Receptor abnormalities • Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

6. 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.

7. Perception • Psychological variables • Interests • Motivation • Expectancy set • Emotion • Attitudes • Values

8. Gestaltists • Gestalt means “whole” in German. The Gestaltists believed that people look to form patterns and complete whole images when they perceive things around them

9. Sensation and Perception

10. Sensation • Our sensory and perceptual processes work together to help us sort out complex processes

11. Sensation and Perception

12. Perceptually Impaired • Iti soft ennotre alized howcom plexT heproces sofrea ding is. Afe w sim plerear rang mentscan ha veyoucomp lete lycon f used!

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

14. 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.”

15. Sensation- 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

16. Sensation- Thresholds • Absolute Threshold • minimum stimulation needed to detect a particular stimulus 50% of the time • Difference Threshold • minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND)

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

18. 100 Percentage of correct detections 75 50 Subliminal stimuli 25 0 Low Absolute threshold Medium Intensity of stimulus Sensation- Thresholds • Subliminal • When stimuli are below one’s absolute threshold for conscious awareness

19. Sensation- 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% • Ex. A three way bulb

20. Weber’s Law

21. Vision

22. Vision • 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

23. 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. Blind Spot

25. Vision- Stabilized Images on the Retina

26. Vision • 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

27. Vision • 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

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

29. Vision • Farsighted Nearsighted Normal • Vision Vision Vision

30. Vision • Hue • dimension of color determined by wavelength of light • Intensity • amount of energy in a wave determined by amplitude • brightness • loudness

31. The spectrum of electromagnetic energy

32. 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 Properties of Waves

33. 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

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

36. Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design

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

38. Afterimages

39. Opponent Process- Afterimage Effect

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

41. Pathways from the Eyes to the Visual Cortex

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

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

44. How the Brain Perceives

45. Illusory Contours

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

49. The Ear Dr. Fred Hossler/ Visuals Unlimited

50. The Ear • Pinna- the external funnel shaped portion of the ear • External Auditory Canal -directs sound waves to the eardrum • Eardrum- thin piece of skin that vibrates to incoming sound