1. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 1 Sensation and Perception 4

2. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 2 Sensation: Receiving Messages About the World Sense organs –See, hear, taste, smell, touch, balance, and experience the world –Sensory receptor cells transmit sensation –Perception – interpreting information and forming images –Stimulus Sensation and Perception

3. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 3 Translating Messages for the Brain Transduction – translates one form of energy (incoming stimuli) into another (sensory information) –Receptor cells to neural impulses Sensation and Perception

4. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 4 Sensory Limits: How Strong Must Messages Be? Threshold – lower limits Absolute threshold – smallest to be detected Difference threshold – smallest difference between 2 stimuli to be detected 50% of time Sensory adaptation – one’s sensitivity to a stimulus varies from time to time –Fatigue, inattention, repeated exposure Sensation and Perception

5. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 5 Sensory Thresholds Vision A candle flame seen at 30 mi. on a clear, dark night Hearing The tick of a watch under quiet conditions at 20 ft. Taste One teaspoon of sugar in 2 gallons of water Smell 1 drop of perfume diffused into the entire volume of a 3 room apartment Touch The wing of a bee falling on your cheek from a height of 1 cm

6. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 6 Sensory Limits: How Strong Must Messages Be? Psychophysics – studies sensory-related matters Weber’s law – amount of change needed for detection 50% of time is always in direct proportion to intensity of original stimulus Sensation and Perception

7. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 7 Vision: Sensing Light Light –Electromagnetic radiation Waves - frequency Wavelength – determines hues seen Intensity – brightness –The more wavelengths in light, the less saturated or pure its hue is Sensation and Perception

8. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 8 The Eye: How Does It Work? Light passes through cornea Iris regulates light through pupil into lens Lens held in place by ciliary muscle Retina has rods and cones for receptors Fovea – center of retina Visual acuity – clarity and sharpness Sensation and Perception

9. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 9 The Eye Cornea Iris Pupil Lens Ciliary muscle Retina Fovea Optic nerve

10. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 10 Photoreceptors Cones Rods

11. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 11 The Eye Rods –Not located in fovea –Responsible for peripheral vision –Hundreds of times more sensitive to light than cones –Produce images perceived with less visual acuity than cones –Do not detect color Sensation and Perception

12. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 12 The Eye Cones –Give brain more precise information –Code information about color –Respond only in bright light Optic nerve – has no cones or rods Blind spot – no visual reception in optic nerve Optic chiasm Sensation and Perception

13. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 13 Vision Optic chiasm Optic nerve Blind spot

14. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 14 Dark and Light Adaptation Dark adaptation –Receptors receive new supply of chemicals –After 30 minutes in the dark - level of sensitivity about 100,000 times greater than in bright light Light adaptation –Rods and cones highly responsive – overload –Bleaching out of receptor chemicals occurs Sensation and Perception

15. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 15 Vision Night blindness – vitamin A deficiency Color vision –Wavelengths determine colors seen –Any color can be created from combinations of red, blue, and green Trichromatic theory – 3 kinds of cones in eye responding mostly to light in either red, blue, or green range of wavelengths Sensation and Perception

16. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 16 Trichromtic theory (Young-Helmholtz)

17. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 17 Color Vision Color afterimages –Complementary colors – yellow and blue, red and green –Prolonged staring causes ghostly afterimage in complementary colors –Occurs in all for complementary colors Sensation and Perception

18. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 18 Color Vision Opponent-process theory –Two kinds of color-processing mechanisms receiving messages from three kinds of cones –Each mechanism responds in opposite ways corresponding to two pairs of complementary colors Sensation and Perception

19. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 19 Fast Slow Opponent-Process Theory (Hering)

20. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 20 Color Blindness Affects about 8% of males, 1% of females Partial color blindness – difficulty distinguishing between two colors –Red-green blindness due to genetic defect –Yellow-blue blindness due to absence of blue pigment in cones Sensation and Perception

21. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 21 Color Blindness

22. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 22 Hearing: Sensing Sound Waves Audition - detection of sound waves Frequency of cycles –Compression – increased density of waves –Rarefaction – reduced density of waves –Determines pitch of sound –Intensity measured in decibel (db) units Prolonged exposure to over 85 db causes hearing loss –Timbre – quality of sound Sensation and Perception

23. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 23 Maximum level of industrial noise considered safe Characteristics of Sound Waves 204060801001600120180140 Loud thunder or rock concert Pain Threshold City bus Normal conversation Subway db Noisy automobile Absolute threshold of human hearing Quiet office Whisper Rocket launch

24. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 24 The Ear: How Does It Work? Outer ear –Pinna – external part of ear that collects sound –External auditory canal – connects outer and middle ear Middle ear –Cardum – tympanic membrane; 1st structure –Eardrum - outermost structure of middle ear Passes vibration to interconnected bones (hammer, anvil, and stirrup) Sensation and Perception

25. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 25 The Ear Pinna External auditory canal Eardrum Hammer Anvil Stirrup Oval window Cochlea Round window Semicircular canals Nerve to brain Eustachian tube Outer earMiddle earInner ear

26. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 26 The Ear Cochlea Oval window Round window Basilar membrane Hair cells

27. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 27 The Ear: How Does It Work? Inner ear –Oval window – eardrumlike structure at end of cochlea –Round window – eardrumlike structure at other end of cochlea –Basilar membrane – forms floor for ear’s sensory receptors –Organ of Corti – contains hairlike receptor cells Sensation and Perception

28. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 28 Body Sensations: Messages About Myself Orientation and movement –Vestibular organ – 2 sets of sensory structures Semicircular canals Saccule and utricle –Kinesthetic receptors – throughout body Skin senses –Pressure sensitivity –Temperature sensitivity Sensation and Perception

29. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 29 The Skin Senses Pressure Free nerve endings Tactile discs hair Specialized end bulbs basket cell around hair Temperature

30. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 30 BACDEG Braille Alphabet HI UW F STXYZV LNJKOPQRM

31. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 31 Pain Nerve endings in body act as nocioceptors –Neural messages transmitted along two distinct pathways Rapid – detects first pain sensation Slow – detects second long-lasting pain –Endorphins and endogenous morphine Sensation and Perception

32. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 32 Pain Nerve endings in body act as nocioceptors –Pain gates regulate pain signals in 3 areas Brain stem – gate-control theory of pain Spinal cord Peripheral regulation of pain –Phantom limbs Up tp 70% of amputees experience this Sensation and Perception

33. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 33 Direction of pain message neuro- transmitter molecules in axon of slow- pain neuron Endorphin receptor Axon of inhibitory pain gate neuron endorphin Neuron in slow-pain fiber Inhibitory pain gate neuron Stimulation of endorphin receptors inhibits firing of axon of slow-pain neuron Close-up view of inhibitory pain gates Somatosensory area of cortex Limbric system Area of pain gates Pathway of fast-pain fibers Pathway of slow-pain fibers Gate-control theory of pain

34. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 34 Human Diversity: Culture and Pain Bariba society – cultural emphasis on pain –Tolerate pain easily –Calm response to pain is part of Bariba pride –Pregnant women don’t show labor pain reaction, experience labor pain and birth alone Medical professionals can overestimate or underestimate effects of pain if impact of culture is not considered Sensation and Perception

35. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 35 Chemical Senses: The Flavors and Aromas of Life Senses of gustation (taste) and olfaction (smell) differ from all other senses –Taste cells and papillae on tongue –Taste buds detect Sensation and Perception Sweetness - mostly sugars Sourness - mostly acids Saltiness - mostly salts Bitterness - toxins, chemicals Fattiness - fats

36. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 36 Surface of tongue Receptor cells Pore Bitter Sour Salty Sweet and fatty Sensory nerve fiber Taste

37. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 37 Chemical Senses: The Flavors and Aromas of Life Olfaction –Olfactory epithelium – top of nasal cavity –Pheromone detection of sweat and urine Vomeronasal organ Influence human female reproductive cycles Inhalation of male sex hormone and mood changes Males may respond to sex hormones Sensation and Perception

38. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 38 Olfactory nerve to brain Olfactory epithelium Nasal cavity

39. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 39 Perception: Interpreting Sensory Messages Perception –Some unique aspects in different cultures –There is some common reality in shared world Visual perception –Perceptual organization Figure-ground Continuity Proximity Sensation and Perception Similarity Closure

40. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 40 Laws of Perceptual Organization Figure-Ground

41. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 41 Laws of Perceptual Organization Law of Continuity Law of Proximity

42. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 42 Laws of Perceptual Organization Law of Closure Law of Similarity

43. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 43 Perception: Interpreting Sensory Messages Sensation and Perception Perceptual Constancy –Brightness constancy –Color constancy –Size constancy –Shape constancy

44. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 44 Depth Perception Retina has two-dimensional surface Monocular cues – perception of one eye –Texture gradient –Linear perspective –Superposition –Shadowing Sensation and Perception –Speed of movement –Aerial perspective –Accommodation –Vertical position

45. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 45 Depth Perception Sensation and Perception Binocular cues – perception with two eyes –Convergence –Retinal disparity Visual Illusions –Ponzo illusion –Vertical-horizontal illusion Color perception –Zollner illusion –Moon illusion –Poggendorf illusion

46. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 46 Visual Illusions The Ponzo Illusion The Müller - Lyer Illusion

47. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 47 Visual Illusions Kanizsa square ED R

48. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 48 Multisensory Integration Integrate and interpret information from multiple senses simultaneously –Limited ability and accident occurrence Motivation, Emotion, and Perception –Motivation and emotions influence perception Past experiences influence all perceptions Sensation and Perception

49. © 2007 The McGraw-Hill Companies, Inc. All Rights Reserved Slide 49 The End 4 Sensation and Perception