PSY 3044 - LECTURES > Sensation & Perception

I. SENSATION, PERCEPTION, and PSYCHOPHYSICS

A. Sensation and perception

1. Sensation is the activation of receptors, such as those in the ears or eyes

2. Perception refers to a brain process of understanding stimulation

3. Transduction means converting physical ('out there') stimulation into electrochemical activity

4. Adaptation is a loss of sensitivity to continued presentation of a stimulus

* IMAGE - A "Flowchart" of Sensory Processing *

B. Psychophysics

1. German psychophysicists of the late-1800's studied the link between stimuli and a
participant's experience

a. Gustav Fechner wrote Elements of Psychophysics (1860)

i. Method of Limits, Adjustment, and Constant Stimuli

* IMAGE - The Method of Limits *

b. Ernst Weber: Weber's Law describes the just noticeable difference (JND)

i. K = JND/S

c. Steven's Power Law and Magnitude Estimation

i. Linear Response, Response Compression, Response Expansion

* IMAGE - Steven's Power Law *

C. Thresholds

1. Absolute threshold: the minimum energy required for 50% detection

2. Differential threshold: smallest amount of stimulation added to a stimulus to produce
50% detection

3. Signal detection theory is a more recent approach that builds on Fechner

II. SENSORY SYSTEMS

A. Vision

1. What we see: The visual stimulus

a. Wavelengths of light are units of energy detected by rods and cones

i. Amplitude and saturation are properties of light waves

ii. Radiant light is visible energy emitted by an object

iii. Reflected light is light waves that are reflected from objects

- difference helps explain additive and subtractive mixture

2. How we see: The visual system

a. Many of the eye's structures are "mechanical," serving to let light waves into
the system

b. When light reaches the retina it eventually triggers bipolar cells

i. These in turn fire ganglion cells, sending signals to the brain

3. The visual pathway

a. Optic nerves meet and cross at the optic chiasm

b. The visual receptors

i. Rods and cones have different shapes, different functions

ii. Vision is clearest when light lands on the fovea

4. Theories of color vision

a. Trichromatic theory

i. Red cones, green cones, blue-violet cones

b. Opponent-process theory

i. Yellow-blue pairs, red-green pairs, brightness pair

5. Color deficiencies

a. Dichromats lack a type of cone

b. Anomalous trichromats process one primary color incorrectly

B. Audition (Hearing)

1. What we hear: The auditory stimulus

a. Sound waves, measured in Hertz, are units of energy for hearing

i. The amplitude of the wave is measured in decibels

2. How we hear: The auditory system

a. Sound waves are sensed from pinna to hair cells

b. Place theory explains some aspects of hearing

c. Frequency theory explains some aspects of hearing

3. Hearing disorders

a. Conduction deafness, sensorineural deafness, and central deafness have different
bases, different prognoses

C. The chemical senses: Taste and smell

1. Taste (Gustation)

a. What we taste: The gustatory stimulus

i. Molecules dissolved in liquid are what gets tasted

b. How we taste: The gustatory system

i. Taste buds, papillae, and microvilli are at work in tasting

2. Smell (Olfaction)

a. What we smell: The olfactory stimulus

i. Molecules in air are what get smelled

b. How we smell: The olfactory system

i. Olfactory receptors, cilia, olfactory bulb are at work

3. The interaction of smell and taste

D. Other sensory systems

1. The vestibular sense

a. Semicircular canals and utricles help with orientation and movement

2. Kinesthetic sense

a. Feedback about the location and position of our body parts

3. Somatosensory processing

a. Information sensed by various skin receptors

b. Pain is often understood through gate control theory

III. PERCEPTION

A. Motivation and attention

1. Motivational influences

a. Divided attention experiments tell us about perception

B. Basic perceptual abilities: Patterns and constancies

1. Pattern perception

a. Discriminating among different figures and shapes

i. Feature analysis theory describes how this happens

2. Perceptual constancies

a. Shape and size constancies remind us we're not in a funhouse

3. Depth perception

a. Binocular cues (such as binocular disparity) help us judge depth

b. Monocular cues (superposition, linear perspective) also help

C. Gestalt principles of perceptual organization

1. Figure and ground comprise a basic perceptual distinction

2. Principles of grouping

a. Proximity, inclusiveness, good continuation, closure

D. Perception of movement

1. Apparent motion is a movement illusion

E. Perceptual hypotheses and illusions

1. The brain devises explanations for the sensory information it puts together

F. Contemporary issues and findings in perception research

1. Parallel processing research sheds light on brain activity during perception

2. Perception is affected by the social context