1 1 Sensation & Perception Chapter 6 Psy 12000.003 Exam 1 • Top Score: 50 • Mean: 43.4 • Median: 44.5 • Mode: 44 • SD: 5.11 • Problems: – Start time screwed up for both; got resolved within 15 minutes – Duplicate question (my fault) – Wrong answers for 3rd graph question (changed within 15 minutes, only affected 5 students; their scores have been corrected) • HELP LINE: 1-800-936-6899 • Suggestions: – No go back? – Others? 2 Announcement • Participants Needed – $10 to participate in experiment. – You (ask a friend, too) • Contact: Eric Wesselmann – [email protected] 3 4 Sensation & Perception How do we construct our representations of the external world? • To represent the world, we must first detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. • Wilhelm Wundt: “Father of Experimental Psychology” – Introspectionism When we select, organize, and interpret our sensations, the process is called perception. 5 The Dark Restaurant • http://www.unsicht-bar.com/unsicht-bar-berlin-v2/en/html/home_1_idea.html “I went to this restaurant in Berlin…” 6 The Senses • Traditional Five: – Sight – Hearing – Touch – Smell – Taste • Six others that humans have – Nociception (pain) – Equilbrioception (balance) – Proprioception & Kinesthesia (joint motion and acceleration) – Sense of time – Thermoception (temperature) – Magnetoception (direction)2 7 Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.” 8 Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THECHT9 Top-Down or Bottom-Up? Learned depth cues make this a top down perceptual distortion 10 Our sensory and perceptual processes work together to help us sort out complex images. Making Sense of Complexity “The Forest Has Eyes,” Bev Doolittle 11 Sensing the World Senses suit an organism’s needs, enabling survival. A frog feeds on flying insects so visual acuity must be very sensitive; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice. 12 Exploring the Senses What stimuli cross our threshold for conscious awareness? Could we be influenced by stimuli too weak (subliminal) to be perceived? Why are we unaware of unchanging stimuli, like a band-aid on our skin?3 13 Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World Light Brightness Sound Volume Pressure Weight Sugar Sweet 14 22nd October 1850 A relative increase in mental intensity, Fechner realized, might be measured in terms of the relative increase in physical energy required to bring it about. Gustav Fechner (1801-1887) 15 No Detection Intensity Absolute Threshold Detected Yes Yes No No Observer’s Response Tell when you (the observer) detect the light. 16 Thresholds Absolute Threshold: Minimum stimulation needed for an individual to detect a particular stimulus 50% of the time. Proportion of “Yes” Responses 0.00 0.50 1.00 0 5 10 15 20 25 Stimulus Intensity (lumens) 17 Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock 18 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 No Yes4 19 Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = δI/I. Stimulus Constant (k) Light 8% Weight 2% Tone 3% 20 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 21 SDT Matrix Decision Yes No Signal Present Hit Miss 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. 22 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it. 23 Now you see, now you don’t 24 Sensation without Perception Video on Visual Prosopagnosia5 25 Sense of Touch The sense of touch is a mix of four distinct skin senses—pressure, cold, warmth, and pain. Bruce Ayers/ Stone/ Getty Images 26 Skin Senses Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. Burning hot Pressure Vibration Vibration Cold, warmth and pain 27 Touch Sensation/Perception • The intense tickling sensation that makes you laugh uncontrollably… – Only happens when someone else tickles you – You cannot tickle yourself and get this response (Blakemore, et al., 2000) • Why? 28 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) 29 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. 30 Taste Scientific American Frontiers: Tasters and Super-tasters6 31 Smell Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell. 32 Age, Gender, and Smell Ability to
View Full Document
Unlocking...