Psych Chapter 4
Psychophysics: Basic Concepts and Issues
o Thresholds: Looking for Limits
o Weighing the Differences: The JND
o Psychophysical Scaling
o Signal-Detection Theory
o Perception without Awareness
o Sensory Adaptation
Our Sense of Sigh: The Visual System
o The Stimulus: Light
o The Eye: A Living Optical Instrument
o The Retina: The Brains Envoy in the Eye
o Vision and the Brain
o Viewing the World in Colour
o Perceiving Forms, Patterns, and Objects
o Perceiving Depth or Distance
o Perceptual Constancies in Vision
o The Power of Misleading Cues: Optical Illusions
o Vision for Perception and Vision for Actions
Our Sense of Hearing: The Auditory System
o The Stimulus: Sound
o Human Hearing Capacities
o Sensory Processing in the Ear.
o Auditory Perception: Theories of Hearing
www.notesolution.com o Place Theory
o Auditory Localization: Perceiving Sources of Sound
o Music and Its Effects
Our Chemical Senses: Taste and Smell
o Taste: The Gustatory System
o Smell: The Olfactory System
Our Sense of Touch: Sensory Systems in the Skin
o Feeling Pressure
o Feeling Pain
Our Other Senses:
o The Kinaesthetic System
o The Vestibular System
Psychophysics Study of how physical stimuli are translated into
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
o Absolute Threshold: Minimum amount of stimulation that an organism can
As stimulus intensity increases, subjects probability of responding to stimuli
www.notesolution.com 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
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.
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.
o Ex: Being in a darkroom, and turning on one light bulb. Second light bulb you
notice a small differen