1 Sensation Chapter 5

2 Sensation & Perception Sensation: detecting physical energy (a stimulus) from the environment & converting it into neural signals. Perception: selection, organization, and interpretation of sensations

3 Top-Down Processing Information processing(perception): brain/mind => experience and expectations => interpretation THE CHT Analysis of the stimulus: sense receptors => brain/mind => interpretation Bottom-up Processing

4 Working Together: Bottom-Up & Top-Down “The Forest Has Eyes,” Bev Doolittle

5 Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World LightBrightness SoundVolume PressureWeight SugarSweet

6 No Detection Intensity Absolute Threshold Detected Yes No Observer’s Response Tell when you (the observer) detect the light.

7 Thresholds Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time. Proportion of “Yes” Responses Stimulus Intensity (lumens)

Some Threshold Tests: 8 -Vision: candle flame on clear, dark night from 30 miles -Hearing: ticking watch in a perfectly quiet room from 20 ft. -Taste: teaspoon of sugar diluted in 2 gallons of water -Smell: drop of perfume diffused through a three room apartment -Touch: the wing of a bee falling on your cheek from a ht. of 1 cm.

9 Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness.

10 “ALL GOOD TEENAGERS, TAKE OFF YOUR CLOTHES”

Subliminal Sensation vs. Subliminal Persuasion Priming can influence feelings Self-help tapes, subliminal ads = no long-term influence on behavior 11

12 Difference Threshold Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold Tell when you (observer) detect a difference in the light. No Observer’s Response NoYes

13 Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. StimulusConstant (k) Light8% Weight2% Tone3%

14 Signal Detection Theory (SDT) Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Person’s experience Expectations Motivation Level of fatigue Carol Lee/ Tony Stone Images

15 SDT Matrix Decision YesNo Signal Present HitMiss Absent False Alarm Correct Rejection The observer decides whether she hears the tone or not, based on the signal being present or not. This translates into four outcomes. NOTE: Signal detection is different for everyone Ex: Soldiers constantly on guard = notice more subtle signals (& false alarms)

17 Sensory Adaptation Constant stimulation = diminished sensitivity Put a band aid on your arm and after awhile you don’t sense it.

18 Now you see, now you don’t Even vision can suffer from desensitization.

19 Vision

20 Transduction Sensory Transduction: transformation of stimulus energy into neural impulses. Phototransduction: Conversion of light energy into neural impulses that the brain can understand.

21 Hue (color): determined by the wavelength (peak to peak) of the light. The Stimulus Input: Light Energy

22 Wavelength (Hue) Different wavelengths of light result in different colors. 400 nm 700 nm Long wavelengths Short wavelengths Violet IndigoBlue Green Yellow OrangeRed

23 Intensity (Brightness) Intensity (brightness) Amount of energy in a wave determined by the amplitude.

24 The Eye

25 Parts of the eye 1.Cornea: Transparent tissue where light enters the eye. 2.Iris: Muscle that expands and contracts to change the size of the opening (pupil) for light. 3.Lens: Focuses the light rays on the retina. 4.Retina: Contains sensory receptors that process visual information and sends it to the brain.

26 The Lens Lens changes shape to focus images on the retina. Accommodation: lens changing shape to help focus near or far objects on the retina. Misshapen eyeball: nearsitedness or farsightedness

27 Retina Retina: The light- sensitive inner surface of the eye Contains: -Receptor cells: Rods: b&w; night vision Cones: color; detail -other neurons: (bipolar, ganglion cells) that process visual information.

28 Test your Blind Spot Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At some point the car on the right will disappear due to a blind spot: point where the optic nerve leaves the eye where no receptor cells are located

29 Feature & Shape Detection Feature: Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. Shape: temporal lobe activity occurs as people look at shoes, faces, chairs and houses. What do you see? What does your brain see? Brain uses feature & shape detection together to perceive patterns

30 Visual Information Processing Parallel Processing: brain processes several aspects of the stimulus simultaneously. Ex: brain divides a visual scene; processing allows us to perceive it as a integrated image

31 Theories of Color Vision Trichromatic theory: (Helmholtz) normal retina contains three receptors that are sensitive to red, blue and green colors. - Colorblindness (red-green) supports this theory Ishihara Test

34 Staring at the green “deadens” the green neurons; thus the red fire Theories of Color Vision Opponent-Process theory: (Hering) we process four primary colors combined in pairs of red- green, blue-yellow, and black-white.

Color processing occurs in two stages: 1) Response to stimuli (Trichromatic) 2) Signals are processed/transmitted to visual cortex (Opponent-Process) 41 Theories of Color Vision

42 Color Constancy Color of an object remains the same under different illuminations. However, when context changes the color of an object may look different. R. Beau Lotto at University College, London

43 Audition

44 The Stimulus Input: Sound Waves Acoustical transduction: Conversion of sound waves into neural impulses - sound influenced by amplitude, frequency, wavelength

45 Loudness of Sound 70dB 120dB Richard Kaylin/ Stone/ Getty Images

46 The Ear Dr. Fred Hossler/ Visuals Unlimited

47 The Hearing Process Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals. 1)Outer ear funnels sound waves to the eardrum 2)Bones of mid. ear relay vibrations through oval window into fluid-filled cochlea 3)Pressure changes in cochlear fluid bends hair cells 4)Hair cell movements trigger nerve cells => auditory nerve 5)Auditory nerve => thalamus => auditory cortex

48 Theories of Audition Place Theory: sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch. (best explains sensing high pitches)

49 Theories of Audition Frequency Theory: rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. (best explains sensing low pitches) Sound Frequency Auditory Nerve Action Potentials 100 Hz 200 Hz

50 Localization of Sounds Sounds that reach one ear faster than the other ear cause us to localize the sound.

51 Hearing Loss Conduction Hearing Loss: damage to the mechanical system that conducts sound waves to the cochlea. Sensorineural Hearing Loss: caused by damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness. (more common) Cochlear implants are electronic devices that enable the brain to hear sounds.

52 Hearing Deficits Can you hear that cell phone? Older people tend to hear low frequencies well but suffer hearing loss when listening for high frequencies.

53 Other Important Senses The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain. Bruce Ayers/ Stone/ Getty Images

54 Pain Biopsychosocial Influences Gate-Control Theory ( Melzak and Wall (1965, 1983)) –spinal cord contains neurological “gates” that either block pain or allow it to be sensed.

55 Pain Control Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction. Todd Richards and Aric Vills, U.W. ©Hunter Hoffman,

56 Taste Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”. Sweet Sour Salty Bitter Umami (Fresh Chicken)

57 Smell Odorants enter the nasal cavity to stimulate 5 million receptors in the Olfactory Bulb to sense smell.

Age, Gender, and Smell Ability to identify smell peaks during early adulthood, but steadily declines after that. Women are better at detecting odors than men.

59 Smell and Memories The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell.

60 Body Position and Movement The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position. Whirling Dervishes Wire Walk Bob Daemmrich/ The Image Works

61 Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor. Synaesthesia – rare condition where one sensation produces another (ex: hearing a sound produces a vision of a color)