Sensation and Perception

1. 4 Sensation and Perception

2. Sensation and Perception 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

3. Sensation and Perception Translating Messages for the Brain • Transduction – translates one form of energy (incoming stimuli) into another (sensory information) • Receptor cells to neural impulses

4. Sensation and Perception 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

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

6. Sensation and Perception 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

7. Sensation and Perception 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

8. Sensation and Perception 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

9. The Eye Retina Lens Cornea Iris Fovea Pupil Ciliary muscle Optic nerve

10. Photoreceptors Rods Cones

11. Sensation and Perception 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

12. Sensation and Perception 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

13. Vision Optic nerve Optic chiasm Blind spot

14. Sensation and Perception 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

15. Sensation and Perception 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

16. Trichromtic theory (Young-Helmholtz)

17. Sensation and Perception 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

18. Sensation and Perception 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

19. Fast Slow Slow Fast Opponent-Process Theory (Hering)

20. Sensation and Perception 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

21. Color Blindness

22. Sensation and Perception 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

23. Characteristics of Sound Waves Maximum level of industrial noise considered safe Pain Threshold 0 20 40 60 80 100 120 140 160 180 db Whisper Normal conversation Loud thunder or rock concert Rocket launch City bus Absolute threshold of human hearing Quiet office Noisy automobile Subway

24. Sensation and Perception 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)

25. Outer ear Middle ear Inner ear Semicircular canals Hammer Anvil Nerve to brain Cochlea Eustachian tube Pinna Stirrup Eardrum Oval window Round window External auditory canal The Ear

26. The Ear Cochlea Oval window Round window Hair cells Basilar membrane

27. Sensation and Perception 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

28. Sensation and Perception 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

29. Pressure Temperature Free nerve endings hair Tactile discs Specialized end bulbs basket cell around hair The Skin Senses

30. Braille Alphabet A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

31. Sensation and Perception 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

32. Sensation and Perception 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

33. Stimulation of endorphin receptors inhibits firing of axon of slow-pain neuron Somatosensory area of cortex neuro-transmitter molecules in axon of slow-pain neuron Limbric system Endorphin receptor Direction of pain message endorphin Area of pain gates Axon of inhibitory pain gate neuron Neuron in slow-pain fiber Pathway of fast-pain fibers Close-up view of inhibitory pain gates Pathway of slow-pain fibers Inhibitory pain gate neuron Gate-control theory of pain

34. Sensation and Perception 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

35. Sensation and Perception 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 Sweetness - mostly sugars Sourness - mostly acids Saltiness - mostly salts Bitterness - toxins, chemicals Fattiness - fats

36. Receptor cells Surface of tongue Pore Bitter Sour Salty Sweet and fatty Sensory nerve fiber Taste

37. Sensation and Perception 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

38. Olfactory nerve to brain Olfactory epithelium Nasal cavity

39. Sensation and Perception 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 • Similarity • Closure

40. Laws of Perceptual Organization Figure-Ground

41. Laws of Perceptual Organization Law of Proximity Law of Continuity

42. Laws of Perceptual Organization Law of Similarity Law of Closure

43. Sensation and Perception Perception: Interpreting Sensory Messages • Perceptual Constancy • Brightness constancy • Color constancy • Size constancy • Shape constancy

44. Sensation and Perception Depth Perception • Retina has two-dimensional surface • Monocular cues – perception of one eye • Texture gradient • Linear perspective • Superposition • Shadowing • Speed of movement • Aerial perspective • Accommodation • Vertical position

45. Sensation and Perception Depth 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. Visual Illusions The Ponzo Illusion The Müller - Lyer Illusion

47. E D R Visual Illusions Kanizsa square

48. Sensation and Perception 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

49. Sensation and Perception 4 The End