Chapter 3 Sensation and Perception

1. Chapter 3Sensation and Perception

2. Chapter 3 Overview • The process of sensation • Vision • Hearing • Smell and taste • The skin senses • Balance and movement • Influences on perception • Principles of perception • Unusual perceptual experiences

3. The Process of Sensation • Sensation is the process through which the senses pick up visual, auditory, and other sensory stimuli and transmit them to the brain • Perception is the process by which the brain actively organizes and interprets sensory information

4. What is the difference between the absolute threshold and the difference threshold? • What isthe softest sound you can hear and the dimmest light you can see? • How much must the volume be turned up or down for you to notice a difference in the loudness of music? • Researchers in sensory psychology have performed many experiments to answer these kinds of questions

5. Absolute threshold • The minimum amount of sensory stimulation that can be detected 50% of the time

6. Difference threshold • The smallest increase or decrease in a physical stimulus required to produce a difference in sensation that is noticeable 50% of the time • Just noticeable difference (JND) is the smallest change in sensation that a person is able to detect 50% of the time

7. Weber’s Law • The JND for all senses depends on a proportion or percentage of stimulus change rather than on a fixed amount of change • A 2% change is needed for a JND in a weight you are holding • a 1 lb difference is needed for a JND in a 50 lb weight • a 2 lb difference is needed for a JND in a 100 lb weight • Only a 0.33% change is needed for a JND in the pitch of a sound • Weber’s law best applies to people with average sensitivities and to stimuli that are not too strong or weak

8. How does transduction enable the brain to receive sensory information? • Sensory receptors are highly specialized cells in the sense organs that detect and respond to one type of sensory stimuli and transduce (convert) the stimuli into neural impulses • Transduction is the process through which sensory receptors convert sensory stimulation into neural impulses • Sensory adaptation is the process in which sensory receptors grow accustomed to constant, unchanging levels of stimuli over time • e.g., Smokers grow accustomed to smell of cigarettes

9. Vision • Our eyes respond to light in the visible spectrum • The band of electromagnetic waves visible to the human eye • Electromagnetic waves are measured in wavelengths • The distance from the peak of a light wave to the peak of the next wave

10. How does each part of the eye function in vision? • Cornea • Tough, transparent protective layer that covers front of eye • Bends light rays inward through the pupil • Lens • Transparent disk-shaped structure behind the iris and pupil • Changes shape as it focuses on objects at varying distances • This process is called Accommodation

11. How does each part of the eye function in vision? • Retina • Contains sensory receptors for vision • Rods • Receptor cells that allow eye to respond to low levels of light • Cones • Receptor cells that enable us to see color and fine detail • Fovea • Area at center of retina that provides the clearest and sharpest vision • Blind spot • Point in each retina where there are no rods or cones

12. What path does visual information take from the retina to the primary visual cortex? • Optic nerve • Caries visual information from each retina to both sides of the brain • Primary visual cortex • Part of the brain in which visual information is processed • Feature detectors respond to specific visual patterns, such as lines or angles

13. How do we detect the difference between one color and another? • An apple’s skin looks red because it absorbs short wavelengths and reflects long wavelengths • Hue • The specific color perceived • Saturation • The purity of a color • Brightness • The intensity of the light energy that is perceived as a color

14. What two major theories attempt to explain color vision? • Trichromatic Theory • Three types of cones in the retina each make a maximal response to one of three colors- blue, green, or red • Opponent-Process Theory • Three kinds of cells respond by increasing or decreasing their rate of firing when different colors are present • Red/green cells • Yellow/blue cells • White/black cells

15. A negative afterimage

16. Hearing • Sound requires a medium, such as air or water, through which to move • First demonstrated by Robert Boyle in 1660 • Watch in a jar experiment

17. What determines the pitch and loudness of sound, and how is each quality measured? • Frequency • The number of cycles completed by a sound wave in one second • Determines the pitch of a sound • Frequency is measured in hertz (Hz) • Amplitude • The loudness of sound • Amplitude is measured in decibels (dB) • Timbre • The distinctive quality of a sound that distinguishes it from other sounds of the same pitch and loudness • Example: A piano and guitar sound different when playing the same note

18. Decibel levels of various sounds Figure 3.5 The loudness of a sound (its amplitude) is measured in decibels. Each increase of 10 decibels makes a sound 10 times louder. A normal conversation at 3 feet measures about 60 decibels, which is 10,000 times louder than a soft whisper of 20 decibels. Any exposure to sounds of 130 decibels or higher puts a person at immediate risk for hearing damage, but levels as low as 90 decibels can cause hearing loss if one is exposed to them over long periods of time.

19. How do the outer ear, middle ear, and inner ear function in hearing? • Outer ear • Visible part of the ear, consisting of the pinna and auditory canal • Middle ear • Contains the ossicles, which connect the ear drum to the oval window and amplify sound waves • Inner ear • Cochlea: Fluid filled chamber that contains the basilar membrane and hair cells • Hair cells: Sensory receptors for hearing

20. What two major theories attempt to explain hearing? • Place theory • Each individual pitch is determined by the particular location along the basilar membrane of the cochlea that vibrates the most • Provides a good explanation of how we hear sounds with frequencies higher than 1000 Hz • Frequency theory • Hair cell receptors vibrate the same number of times per second as the wave sounds that reach them • Provides a good explanation of how we hear low-frequency sounds

21. Smell and Taste • Olfaction • The sense of smell • Gustation • The sense of taste

22. What path does a smell message take from the nose to the brain? • Olfactory epithelium • Two 1-inch square patches of tissue, one at the top of each nasal cavity, which contain olfactory neurons • Olfactory bulbs • Two structures above the nasal cavity where smell sensations first register in the brain • Orbitofrontal cortex • Receives messages from olfactory bulbs via the thalamus

23. What are the primary taste sensations, and how are they detected? • Traditionally, four primary taste sensations have been recognized • Sweet • Sour • Salty • Bitter • Recent research suggests that there is a fifth taste sensation • Umami • This sensation is triggered by glutamate

24. What are the primary taste sensations, and how are they detected? • Taste sensations are detected by receptor cells in the taste buds • Specialized receptors are activated by each flavor (sweet, sour, etc.) • These receptors send separate messages to the brain

25. The Skin Senses • Include the senses of touch and pain • These senses are critical for survival

26. How does the skin provide sensory information? • When an object touches and depresses the skin it stimulates receptors in the skin • These receptors send messages through nerve connections to the spinal cord, through the brainstem and midbrain, and to the somatosensory cortex • Areas on the skin vary in sensitivity to touch, as measured by the two-point threshold • Areas with greater sensitivity are more densely packed with touch receptors

27. What is the function of pain, and how is pain influenced by psychological factors, culture, and endorphins? • Pain serves as an early warning system for many potentially deadly situations • Pain can be influenced by several psychological factors • Focusing attention elsewhere reduces pain • Placebo effect reduces pain • Negative thoughts increase pain • Some cultures encourage individuals to suppress, or exaggerate, emotional reaction to pain • Endorphins are the body’s natural painkillers • They block pain and produce a sense of well-being

28. Balance and Movement • The kinesthetic and vestibular senses provide information about where the parts of the body are and where the body is located relative to the physical environment

29. What kinds of information do the kinesthetic and vestibular senses provide? • Thekinesthetic sense provides information about the position of body parts in relation to each other and the movement of the entire body or its parts • This information is detected by receptors in the joints, ligaments, and muscles

30. What kinds of information do the kinesthetic and vestibular senses provide? • The vestibular sense detects movement and the body’s orientation in space • The vestibular sense organs are located in the semicircular canals and vestibular sacs in the inner ear • These organs sense rotation of the head

31. Influences on Perception • Perception isthe process through which the brain assigns meaning to sensations • Perception is influenced by a number of factors, including • Attention • Prior knowledge • Cross-modal perception

32. What is gained and what is lost in the process of attention? • Attentionis the process of sorting through sensations and selecting some of them for further processing • When attention is focused on some sensations, others are missed altogether or misperceived • Inattentional blindness occurs when attention is shifted from one object to another and we fail to notice changes in objects not receiving direct attention • The cocktail party phenomenon shows that we focus attention on information that is personally meaningful

33. How does prior knowledge influence perception? • Bottom-up processing • Information processing in which individual bits of data are combined until a complete perception is formed • Top-down processing • Information processing in which previous experience and knowledge are applied to recognize the whole of a perception • Perceptual set is an expectation of what will be perceived that can affect what is perceived

34. How does information from multiple sources aid perception? • Cross modal perception • The process by which the brain integrates information from more than one sense • Cross modal perception is used to process complex stimuli such as speech

35. Principles of Perception • A few principles govern perceptions in all humans

36. What are the principles that govern perceptual organization? • Gestalt principles of perceptual organization • Similarity: Objects that have similar characteristics are perceived as a unit • Proximity: Objects that are close together are perceived as belonging together • Continuity: Figures or objects are perceived as belonging together if they appear to form a continuous pattern • Closure: Figures with gaps in them are perceived as complete

37. What are some of the binocular and monocular depth cues? • Depth perception • The ability to perceive the visual world in three dimensions and to judge distances accurately • Binocular depth cues depend on both eyes working together • Convergence • Binocular disparity • Monocular depth cues can be perceived by one eye alone

38. Binocular disparity • Enables most of us to see 3-D images in stereograms

39. Monocular depth cues

40. How does the brain perceive motion? • The brain perceives real motion by comparing the movement of images across the retina to reference points that it assumes to be stable • Autokinetic illusion • An unmoving light in a dark room appears to move • Your eyes are moving, not the light • In the dark, the brain has no stable reference point to determine what is moving

41. What are three types of puzzling perceptions? • Ambiguous figures • The perceptual system tries to resolve the uncertainty by seeing the figure first one way and then another • Impossible figures • May not seem unusual until you examine them closely and see the impossibility

42. What are three types of puzzling perceptions? • Illusions • False perceptions or misperceptions of an actual stimulus in the environment • Figure c shows the Müller-Lyer illusion • Figure d shows the Ponzo illusion

43. Unusual Perceptual Experiences • Subliminal perception • The capacity to perceive and respond to stimuli that are presented below the threshold of awareness • Extrasensory perception (ESP) • Gaining information about objects, events, or another person’s thoughts through means other than known sensory channels

44. In what ways does subliminal perception influence behavior? • Research suggests that subliminal information can influence behavior to some degree • But it appears to be ineffective at persuading people to buy products or vote in certain ways

45. What have studies of ESP shown? • Some studies have suggested that ESP exists • But, in almost all cases, attempts to replicate these studies have failed • So most psychologists remain skeptical about existence of ESP