Sensation and Perception

1. Sensation and Perception

2. ABOUT ME ABU BAKAR NATIONALITY : PAKISTAN CITY : SIALKOT, PUNJAB MARITAL STATUS : SINGLE Tel: (+92) 322 7967172 E-Mail: abubakarmehmood786@yahoo.com PERSONAL PROFILE CONTACT INFO THE CREATOR ACADEMY thecreatorsacademyofficial The Creators Academy thecreatorsacademyofficial BS(HONS) PHYSICS UNIVERSITY OF SIALKOT UCQxAo-GBHUI2l9_LBYicsRw FOUNDER EDUCATION ORIGIN LAB, VIRTUAL LAB, ENDNOTE SOFTWARE, EMATHHELP SOFTWARE , MICROSOFT OFFICE, ADBOBE (PHOTOSHOP & ILUUSTRATOR), ARDUINO SOFTWARE, AMAZON VITUAL ASSISTAN, VIDEO EDITTING, SOCIAL MEDIA ACCOUNT MANAGEMENT URDU, PUNJABI, ENGLISH, ARABIC ABUBAKAR692909 @abubakar786786 Abubakar Bhutta @_abubakar786 ABU BAKAR SOCIAL MEDIA SKILLS & LANGUAGE

3. What are Sensation and Perception? • “I have perfect vision” –Heather Sellers has problem with her perception. She cannot recognize faces-prosopagnosia (face blindness) “In college, on a date at the Spaghetti Station, I returned from the bathroom and plunked myself down in the wrong booth, facing the wrong man. I remained unaware he was not my date even as my date (a stranger to me) accosted Wrong Booth Guy, and then stormed out of the Station. I can’t distinguish actors in movies and on TV. I do not recognize myself in photos or video. I can’t recognize my stepsons in the soccer pick-up line; I failed to determine which husband was mine at a party, in the mall, at the market” This curious mix of “perfect” vision and face blindness illustrates the distinction between sensation and perception.

4. 1. What are Sensation and Perception? • Her Sensation-the stimulation of sensory receptors and transmission of sensory information to the central nervous system, is normal. • Her Perception- the process by which sensations are organized and interpreted to form an inner representation of the world, is almost normal. • She recognizes people from their hair, etc., but not face

5. 2. Absolute Threshold • Weakest amount of a stimulus that can be distinguished from no stimulus at all • Detected 50% of the time

6. 2. Absolute Threshold • Weakest amount of a stimulus that can be distinguished from no stimulus at all • Detected 50% of the time

7. 3. Difference Threshold • Minimum difference in magnitude of two stimuli required to tell them apart • Detected 50% of the time • Weber’s constant • Standard of difference - Light – 2% of intensity - Weight – 2% of weight - Sound – one-third of 1% change in pitch (frequency) -Taste – 20% difference in saltiness

8. 4. Influences on Perception • Stimulus characteristics and psychological factors interact to influence whether a stimulus is detected. • Psychological factors such as learning, motivation, and psychological states (attention) • Perceptual set- what we expect to perceive - Rosenhan et al., (1973) • Attention (Inattentional blindness) • Social perception

9. 5. Transduction & Adaptation • Sensory receptors- detect and respond to one type of sensory stimuli- light, smell, etc. • Transduction-the sensory receptors convert the sensory stimulation into neural impulses. • After a time, the sensory receptors grow accustomed to constant, unchanging levels of stimulus-sights, smell, etc.- we notice it less & less- adaptation

10. 6. VisionLight • Spectrum of electromagnetic energy • Vary in wavelength • Human eyes can perceive only a very thin band of electromagnetic waves, known as the visible spectrum (400 – 700nanometers) • Within visible light, color is determined by wavelength

11. The Visible Spectrum

12. The Eye • Light enters through a narrow opening • Cornea – transparent eye cover • Iris – muscle; colored part of the eye • Pupil – opening in the iris • Sensitive to light and emotion

13. Transmission of Light Through the Eye PLAY VIDEO

14. 8. The Eye • Light Sensitive Surface • Retina • Photoreceptors • Rods, Cones, Bipolar and ganglion cells • Optic Nerve • Axons of ganglion neurons form optic nerve • Conducts sensory input to brain (occipital lobe)

15. Anatomy of the Eye PLAY VIDEO After clicking ‘Play Video’ use your mouse to manipulate this active figure.

16. 9. Rods and Cones • Cones • Most densely packed in center of retina (fovea) • Provide color vision, fine details • Rods • Provide vision in black and white • More sensitive to dim light than cones

17. 10. Visual Acuity • Greatest in the fovea • Blind spot (demonstration/handouts) • Point in retina where ganglion cells converge • Nearsightedness, image in front of retina • Farsightedness-behind • Presbyopia

18. 11. Light Adaptation • Dark adaptation • Process of adjusting to lower lighting • Cones reach maximum adaptation in about 10 minutes • Rods continue to adapt up to 45 minutes • Adaptation to bright light • Process occurs within a minute or so

20. Perceptual Dimensions of Color • Afterimage • Persistent sensations of color are followed by perception of the complementary color when the first color is removed

21. 12. Theories of Color • Trichromatic Theory • Three types of cones • Sensitive to red, green, or blue • Opponent-Process Theory • Three types of color receptors • Red-green, blue-yellow, and light-dark

22. 13.Color Blindness • Trichromat • Normal color vision • Monochromat • Totally color blind • Dichromat • Partial color blindness • Discriminate between two colors (red & green, or blue &yellow) • More common in males (sex linked trait)

23. Plates from a Test for Color Blindness

24. Visual PerceptionLecture 7

25. 1. Visual Perception • Process used to organize sensory impressions caused by the light that strikes our eyes • Sensation is a mechanical process • Perception is an active process • Involves experience, expectations and motivations

26. 1. Visual Perception • Process used to organize sensory impressions caused by the light that strikes our eyes • Sensation is a mechanical process • Perception is an active process • Involves experience, expectations and motivations

27. 1. Visual Perception • Process used to organize sensory impressions caused by the light that strikes our eyes • Sensation is a mechanical process • Perception is an active process • Involves experience, expectations and motivations

28. 2. Perceptual Organization • Figure – Ground Perception • Ambiguous, unstable figures, we shift back & forth

29. Gestalt Rules for Perceptual Organization

30. 3. Gestalt Rules for Perceptual Organization • Common Fate • Elements moving together are grouped together (runners) • Closure • Fit bits of information into familiar patterns; • Perception of a complete figure, even when there are gaps in sensory information • Proximity • Nearness of objects • Similarity • Similarity of objects • Continuity • Series of points having unity

31. 4. Perception of Motion(mini class discussion) • Visual perception of motion is based on change of position relative to other objects • Illusions of movement • Stroboscopic motion (class discussion, how do we know that a train moves?)

32. 5. Depth Perception • Monocular Cues • Perspective • Clearness • Overlapping • Shadows • Texture gradient • Motion parallax • Binocular Cues • Retinal disparity • Convergence

33. 6. Perceptual Constancies • Acquired through experience; creates stability • Size Constancy (video) • Color Constancy • Brightness Constancy • Shape Constancy

34. Size Constancy PLAY VIDEO

35. 7. Visual Illusions • Hering-Hemlholtz Illusion • Perceive drawing as three-dimensional • Müller-Lyer Illusion • Interpret length of lines based on experience

36. Hearing

37. 8. Sound • Sound waves require a medium; air or water • Sound waves compress and expand molecules of the medium, creating vibrations • A single cycle of compression and expansion is one wave of sound • Human ear is sensitive to sound waves with frequencies of 20 to 20,000 cycles per second

38. 9. Pitch and Loudness • Pitch • Frequency (# of cycles per second) • Expressed in hertz (Hz) • Pitch of women’s voice is higher than men’s • Loudness • Height (amplitude) of sound waves • Expressed in decibels (dB)

39. Sound Waves of Various Frequencies and Amplitudes

40. Decibel Ratings of Familiar Sounds

41. 10.The Ear • Shaped and structured to • capture sound waves, • vibrate in sympathy with them, and • transmit auditory information to the brain • Three parts: outer, middle & inner ear.

42. The Human Ear

43. 11.Parts of the Ear • Outer Ear • Funnels sound waves to the eardrum • Middle Ear • Eardrum, hammer, anvil and stirrup • Acts as an amplifier • Oval window – Round window-balances the pressure

44. 12. Parts of the Ear • Inner Ear • Cochlea (3 chambers-two membrane) • Basilar membrane • Organ of Corti- commend post- 25,000 hair cells • Auditory nerve- temporal lobes of cerebral cortex

45. 13. Locating Sounds • Loudness and sequence in which sounds reach the ear provide cues • May turn head to clarify information • Try at home: “Virtual Barber Shop” (requires headphones to be appreciated fully). • Check it out at http://youtube.com/watch?v=IUDTlvagjJA

46. 14. Perception of Loudness and Pitch • Related to number of receptor neurons on the organ of Corti • Sounds are perceived as louder when more sensory neurons fire

47. 15. Perception of Loudness and Pitch • Place theory • Pitch is sensed according to place that vibrates • Frequency theory • Pitch perceived on stimulation of impulses that match the frequency of the sound • Both theories work together

48. 16. Deafness • Conductive deafness • Damage to middle ear • Hearing aids can help • Sensorineural deafness • Damage to inner ear or auditory nerve • Cochlear implants may help with damage to inner ear, but not auditory nerve

49. The Chemical Senses:Smell and Taste

50. Smell • Odors trigger receptor neurons in olfactory membrane • Odors are sample molecules of substances in the air • Sensory information about odors is sent to the brain through the olfactory nerve • Odor contributes to flavor of foods