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Stress and Disease Dr. Donald B. Giddon Harvard University, Fall 2013 Perception and Psychophysics. What is stressful for a given individual?. Objective vs. Subjective Stressors Stimulus/object. R 1. Stimulus/subjective PERCEPTION. R x. Key Concepts. Sensation vs. Perception - PowerPoint PPT Presentation
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Stress and Disease
Dr. Donald B. Giddon Harvard University, Fall 2013
Perception and Psychophysics
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What is stressful for a given individual?
Objective vs. Subjective Stressors
Stimulus/object
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Stimulus/subjectiveStimulus/subjectivePERCEPTIONPERCEPTION
RR11
RRxx
Key Concepts
• Sensation vs. Perception
• Perception - – the key intervening variable between psychosocial
stressors and coping methods
• Psychophysics –– relating subjective to objective measures
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Gestalt Principles of Perceptual Organization Illustrated Through the Use of Illusions
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1. Ambiguity - Figure /Ground, Old/Young Lady, Necker Cube
2. Completion – Kanzisa triangles
3. Context/framing –Ponzo illusion (railroad tracks/vertical lines), Muller Lyer (“wings” at ends of lines)
4. Camouflage - Hidden groups of bird, Dalmations
5. Distortion - Size constancy
6. Facial illusions - Inverted face (Thatcher/Clinton/Gore)
PRINCIPLES OF PERCEPTIONPRINCIPLES OF PERCEPTION
Dr. AndersonDr. Anderson
Sensation
The process by which our sense organs respond to and translate stimuli into
nerve impulses sent to the brain
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• Translation of sensation into perceptiono Stimuli activate sensory receptorso Sensory receptors translate information into nerve
impulses (transduction)o Specialized (2nd and 3rd order) neurons integrate
stimuli featureso Stimulus pieces are reconstructed and compared
to stimuli in memoryo Perception is then the conscious experience of an
organized and meaningful message
The Sensory Systems: Vision
Lens:– Becomes thinner to focus on distant
objects and thicker to focus on closer ones
Rods: Black and white receptors
Cones: Color receptors
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The Sensory Systems: Vision
Transduction
– Absorption of light by photopigments produces a chemical reaction changing the rate of neurotransmitter release at the synapses
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The Sensory Systems: Audition
Characteristics of sound waves
– Frequency/Pitch: the number of sound waves, or cycles, per second (measured in Hz)
– Amplitude/Loudness : the magnitude of the sound waves (measured in dB)
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Examples of Relation of Physical Energy to Perception
• SoundoWavelengthoFrequencyoVolume/DecibelsoToneoTimbre
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Subliminal Perception: Research Results
• Stimuli above threshold influence behavior much more than subliminal stimuli
• Subliminal stimuli may influence attitudes with or without changing behavior
• Effects may be due tooAnticipation and/oro Expectations
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Importance of Audition in Interpersonal CommunicationImportance of Audition in Interpersonal Communication
* Communication facilitation and interference * Communication facilitation and interference
- Clinicians’ masks- Clinicians’ masks-Distortion of context-Distortion of context
- “Masking” of affect and- “Masking” of affect and- Relation to facial expression- Relation to facial expression- Burqa effect- Burqa effect
- Patient compliance- Patient compliance- Cooperation- Cooperation- Adherence to treatment- Adherence to treatment- Health literacy- Health literacy
- Relation to Psychopathology- Relation to Psychopathology
The Sensory Systems: Olfaction
Menstrual Synchrony Tendency of women who live together or are close
friends to become similar in their menstrual cycles May be due to pheromones (Preti et al., 1986), but
synchrony not found in cohabiting lesbian couples (Weller & Weller, 1997, 1998)
• Recall vs. Recognition• Cannot conjure up or recall smells/taste; only recognize
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More important in animals (drug dogs, bloodhounds) evolutionary significance
The Sensory Systems
• Skin Sensationso Humans are sensitive to:
o Pressure (touch)o Tactileo Paino Temperature
WarmCold
• Body Senseso Kinesthesis – movement
o ProprioceptionProvides us with feedback about the position of our
muscles and joints34
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Psychophysics: Relation of Objective to Subjective World
• The Absolute Threshold (R. Limen):
The lowest magnitude at which a stimulus can be detected
o Dimmest light in which we can see objectso Softest sound we can hearo Lowest chemical concentration detected
Gustation Olfaction
The Difference Threshold (D.Limen)
• The difference threshold (just noticeable difference or JND) is the smallest difference between two stimuli.
• Point of subjective equivalence
– Weber’s Law: the JND is directly proportional to the magnitude of the stimulus with which the comparison is made (e.g 1/50 for weight)
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Weber/Fechner Fractions for Sensory/Perceptual Systems
• Vision (brightness) 1/60• Vision (hue) varies• Audition (pitch) 1/333• Audition (loudness) 1/20• Tactile 1/7• Pain (heat) 1/30• Taste (salt) 1/3• Smell (India Rubber) ¼• Changes in facial dimensions
o Recognize diastema (space between teeth)o Recognize angulation (slant of mouth)
Each sensory system has a Power Function relating physical to subjective world.
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•Difference threshold (D. Limen) How much objective change in the stimulus before it can be subjectively detected
oSmallest difference in brightness or hue detectableoRecognizing differences between tones or intensityoDifferences in concentrationoDifferences in angular proportional measures related to body image
Esthetics Orthodontics Plastic surgery
Sensory Adaptation (Habituation)
• Activation of sensory neurons decreases in response to a constant stimulus
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•Other applications
o Relation to word choicee.g., “acceptable”
oPsychodiagnosticso e.g. Rorschach (see next two slides)
Signal Detection Theory
Decision criterion: A personal standard of certainty before indicating that one detects the presence, absence or change of a stimuluso Willingness to respondo Affected by:
Conservativeness or boldnessIncreasing rewards for hits or costs for misses
e.g. response bias Correction by standard scores
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The Role of Perception in Life Experiences
Perceptual schemata: Allow us to classify sensory input in a top-down fashion
Perceptual set: A readiness to perceive stimuli in a particular way
Perceptual constancies: E.g., stereotype response set/rigidity. Allow us to recognize familiar stimuli under varying conditions
Perceptual defense Need determines perception, e.g. Rorschach
Hunger Sex
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Practical Applications of Perceptual TenetsPractical Applications of Perceptual Tenets
• Cosmetic SurgeryCosmetic Surgery• FashionFashion• Architecture/Interior DesignArchitecture/Interior Design• Eyewitness IdentificationEyewitness Identification• “ “Mis”perceptions about life eventsMis”perceptions about life events
– importance of losing a tennis gameimportance of losing a tennis game
- line calls - line calls
-- -- ““Quality of life” (education, housing, recreation, health Quality of life” (education, housing, recreation, health care, employment, security, food)care, employment, security, food)
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