Sensation and Perception

1. Sensation and Perception

2. Sensation and Perception Sight Hearing Smell Taste Touch Vestibular senses

3. Sensation and Perception Physical change in external or internal environments triggers chemical, electrical and mechanical activity in sense receptors. Complex processing by nervous system Pattern of activity in part of brain

4. Sensation and Perception The initial electrical activity is a sensation, a stimulus (colors, forms, sounds, smells, tastes, etc.) that activates a receptor. The initial electrical activity is a sensation: A perception is: a series of organized sensory information that creates meaningful stimuli. + =

5. Sensation and Perception Transduction: sensory process that converts physical energy into the form of neural messages.

6. Sensation and Perception Transduction (smell example) Step 1: Transform one form of energy to another—detection by a sensory neuron of a physical stimulus Stimulus: food aroma Nose detects the stimulus (aroma)

7. Sensation and Perception Transduction Step 2: When the appropriate stimulus (aroma) reaches a sense organ (Niki’s nose), it activates specialized neurons called receptors

8. Sensation and Perception Transduction Step 3: Receptors convert their excitation into a nerve signal that travels along a sensory path- way to specialized sensory processing areas of the brain (in all but smell, the signal travels by way of the thalamus)

9. Sensation and Perception Stimulus = any aspect of or change in the environment to which an organism responds. Stimuli measured many ways: duration, intensity, wavelength

10. Sensation and Perception Sensations occur any time one stimulus activates a receptor. A combination of sensations plus your past experience=perception Absolute threshold --the minimum amount of physical energy required to produce a sensation

11. Sensation and Perception A candle flame can be seen 30- miles away on a dark, clear night The ticking of a watch can be heard 20 feet away under quiet conditions. Perfume can be detected when one drop is put in a three-room apartment.

12. Sensation and Perception The difference threshold --the minimum amount of physical energy change required to produce a change in sensation Weber’s Law --the larger or stronger a stimulus, the larger the change required for an observer to experience a noticeable difference.

13. Sensation and Perception The senses are most responsive to increases and decreases; to new events rather than ongoing, unchanging stimulation

14. Sensation and Perception Sensory Adaptation The senses adapt, or adjust, to constant levels of stimulation. Darkness Noisy streets Let’s do the sensory adaptation Experiment On p. 212. Smelly rooms

15. Sensation and Perception A person’s ability to detect a stimulus also depends on motivation. Individuals decide to receive stimuli, although that decision-making process isusually entirely unconscious,and is often based on feelings or expectations.

16. Sensation and Perception Signal Detection Theory Disputes absolute threshold No sharp boundary between stimuli that you can perceive and stimuli that you cannot perceive Detection thresholds involve recognizing some stimulus against a background of competing stimuli

17. Sensation and Perception Signal Detection Theory Processing stimuli Pre-attentive process—extracting information automatically and simultaneously when presented with stimuli Attentive process—considers only one part of the stimuli presented at a time

18. Sensation and Perception Signal Detection Theory The Stroop Interference Effect (Attentive) Step 1: name the colors in boxes at left rapidly Step 2: read words at right rapidly Step 3: name the colors at right rapidly

19. The Senses Actually more than 5 senses Basic Five: vision, hearing, taste, smell and touch Several skin senses Internal senses: vestibular and kinesthetic

20. The Senses Each type of sensory receptor takes some sort of external stimulus . . . . . . and converts it into a chemical- electrical message that can be understood by the brain. The process of transduction.

21. The Senses Vision

22. The Senses Vision Blind spot Lack of receptors at the spot where the optic nerve connects to the retina

23. The Senses Vision Most studied of all the senses Light enters via the pupil reaches the lens, a flexible structure that focuses light on the retina

24. The Senses Vision Retina contains two types of light- sensitive receptor cells: Rods and cones Those cells change light energy into neuronal impulses, which then travel via the optic nerve to the brain.

25. The Senses Vision Cones require more light than rods before they respond 75-150 million rods; 6-7 mil. cones Only cones are sensitive to color If all or some cones do not function properly: color deficiency 8% Amer. men; 1% Amer. women

26. The Senses We psychology teachers love experiments. So let’s do some about our eyes. Turn to p. 216 in the textbook. We all have blind spots Color deficiencies Negative afterimages

27. The Senses Vision Two eyes two images Combination of 2 images into one is called binocular fusion Images differ on each retina Retinal disparity

28. The Senses Hey-yo! Let’s do another experiment—this one is about retinal disparity. Pen or pencil Hold 12-inches in front of face. Both eyes, then left eye closed, then right eye closed. What happens?

29. The Senses We look with our eyes, but see with our brain

30. The Senses We look with our eyes, but see with our brain

31. The Senses Hearing If a tree falls in the forest, and no one is there to hear it, does it make a sound?

32. The Senses Hearing Depends on vibrations of the air, called sound waves Sound waves from the air pass through various bones and fluids to the inner ear

33. The Senses Hearing The inner ear contains tiny, hair- like cells that move back & forth Hair-like cells change sound vibrations into neuronal signals that travel, via the auditory nerve, to the brain.

34. The Senses Hearing Anvil Hammer Stirrup

35. The Senses Hearing Anvil Hammer Stirrup 1. Airborne sound waves must be relayed to the inner ear. In this initial transformation, vibrating waves of air enter the outer ear and strike the eardrum, or tympanic membrane. This tightly stretched sheet of tissue transmits the vibrations to three tiny bones: the hammer, anvil and stirrup

36. The Senses Hearing Anvil Hammer Stirrup 2. These bones pass vibrations on to the primary organ of hearing, the cochlea (in the inner ear) b. The cochlea focuses the vibrations on the basilar membrane

37. The Senses Hearing 3. The basilar membrane converts the vibrations into neural messages (the swaying of tiny hair cells on the vibrating basilar membrane stimulates sensory nerve endings connected to the hair cells.) The excited neurons transform the mechanical vibrations of the basilar membrane into neural activity.

38. The Senses Hearing 4. Finally, the neural messages travel to the auditory cortex in the brain—neural signals leave the cochlea in a bundle of neurons called the auditory nerve. The neurons from the two ears meet in the brain stem, which passes the auditory information to both sides of the brain

39. The Senses Hearing Perception of loudness depends on amplitude of vibrations in the air. That amplitude, or sound-pressure energy, is measured in decibels. Loudest ear can detect: 140 dbl. Softest Sounds 0 dbls.

40. The Senses Hearing Any sound over 110 dbls can damage hearing . . . . . . as can persistent sounds as low as 80 dbls

41. The Senses Hearing Timbre (pronounced tam-ber): Timbre (pronounced tam-ber): “tone color” or the complex quality of the sound wave. Example: recognizing your company commander’s voice on the radio

42. The Senses Conduction deafness: Conduction deafness: conduction of vibrations has been negatively affected Nerve deafness: Damage to auditory nerve or one of higher auditory processing centers

43. The Senses Hearing Some hearing loss comes as a result of age, however. Mosquito Ring Tone (Teen Buzz) Presbycusis: aging ear; starting around age 20, the human ear loses its ability to hear tones in the highest human-range frequencies (18-20 kHz) and as one ages it becomes more difficult to detect those sounds

44. The Senses Smell and Taste The chemical senses: their receptors are sensitive to chemical molecules rather than to light energy or sound waves Smell: molecules, via vapors, make contact with a special membrane in upper nasal passages where smell receptors are located.

45. Sensation and Perception You may recall that we used smell to describe Transduction Step 1: Transform one form of energy to another—detection by a sensory neuron of a physical stimulus Stimulus: food aroma Nose detects the stimulus (aroma)

46. Sensation and Perception Transduction Step 2: When the appropriate stimulus(aroma) reaches a sense organ(Niki’s nose),it activates specialized neurons called receptors

47. Sensation and Perception Transduction Step 3: Receptors convert their excitation into a nerve signal that travels along a sensory path-way, via the Thalamus, to specialized sensory processing areas of the brain

48. The Senses Smell and Taste Those receptors send messages about smells via the olfactory nerve to the brain. Taste: appropriate chemicals must stimulate receptors in the taste buds of your tongue

49. The Senses Smell and Taste Sour, salty, bitter and sweet Four primary sensory experiences make up taste: Recent research: umami (Asian) Old theory re: smell: six qualities Flowery, fruity, spicy, resinous, putrid, and burned Several smell theories, no conclusions

50. The Senses Smell and Taste Sensations of warmth, cold and pressure . . . . . . affect taste Cold chili; hot soda pop; soggy chips