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Chapter 4

PSY100Y5 Chapter Notes - Chapter 4: Middle Ear, Darkroom, Night Vision

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Dax Urbszat

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Psych Chapter 4
Psychophysics: Basic Concepts and Issues
oThresholds: Looking for Limits
oWeighing the Differences: The JND
oPsychophysical Scaling
oSignal-Detection Theory
oPerception without Awareness
oSensory Adaptation
Our Sense of Sigh: The Visual System
oThe Stimulus: Light
oThe Eye: A Living Optical Instrument
oThe Retina: The Brains Envoy in the Eye
oVision and the Brain
oViewing the World in Colour
oPerceiving Forms, Patterns, and Objects
oPerceiving Depth or Distance
oPerceptual Constancies in Vision
oThe Power of Misleading Cues: Optical Illusions
oVision for Perception and Vision for Actions
Our Sense of Hearing: The Auditory System
oThe Stimulus: Sound
oHuman Hearing Capacities
oSensory Processing in the Ear.
oAuditory Perception: Theories of Hearing

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oPlace Theory
oAuditory Localization: Perceiving Sources of Sound
oMusic and Its Effects
Our Chemical Senses: Taste and Smell
oTaste: The Gustatory System
oSmell: The Olfactory System
Our Sense of Touch: Sensory Systems in the Skin
oFeeling Pressure
oFeeling Pain
Our Other Senses:
oThe Kinaesthetic System
oThe Vestibular System
Psychophysics Study of how physical stimuli are translated into
psychological experience.
Sensation is the stimulation of sense organs.
Perception is the selection, organization, and interpretation of sensory
Thresholds: Looking for Limits
Sensation begins with stimulus (Any detectable input).
Threshold: Dividing point between energy levels that do and do not have a detectable
oAbsolute Threshold: Minimum amount of stimulation that an organism can
As stimulus intensity increases, subjects probability of responding to stimuli
gradually increases.

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Absolute threshold as the stimulus intensity detected 50% of the time.
Weighing the Differences: The JND
Just Noticeable Difference (JND) The smallest difference in the amount of
stimulation that a specific sense can detect.
JND closely related to absolute threshold. Absolute Threshold is simply the JND
from nothing.
Webers Law: States that the size of JND is a constant proportion of the size of the
initial stimulus. The constant proportion is called the Weber Fraction.
Weber Fraction for weights: 1/30. This means you can only tell the difference
between 300 grams and 310 grams, not 300 grams and 305 grams.
Psychophysical Scaling
Scale Judging the increase in sensory input.
Fechners Law The magnitude of a sensory experience is proportion to the number
of JNDs that the stimulus causing the experience is above the absolute threshold.
oEx: Being in a darkroom, and turning on one light bulb. Second light bulb you
notice a small difference. Third one you hardly notice anything different.
Perception cant be measured on absolute scales.
Signal-Detection Theory
Signal-detection theory The detection of stimuli involves decision processes as well
as sensory processes, which are both influenced by a variety of factors besides
stimulus intensity.
Hits Detecting signals when present. Misses Failing to detect signals when
present. False Alarms Detecting signals when not present. Correct Rejections
Not detecting signals when they are absent.
Noise Irrelevant stimuli that interferes with your ability to pick up weak signals.
Perception without Awareness
Subliminal Perception Registration of sensory input without conscious awareness.
(Limen = Threshold, sub = below. Therefore Subliminal = Below Threshold.
Sensory Adaption
Sensory Adaption Gradual decline in sensitivity due to prolonged stimulation.
The Visual System
The Stimulus Light
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