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Ch. 3 - Sensation and Perception Sensation - The experience of sensory
stimulation Perception - The process of creating
meaningful patterns from raw sensory information
1. The Nature of Sensory Processes
A. The Basic Process Receptor Cell- A specialized cell that responds to a
particular type of energy B. Sensory Thresholds
Absolute The least amount of energy that can be detected
50% of the time Adaptation
An adjustment of the senses to the level of stimulation
Sensory Thresholds
Difference The smallest change in stimulation that can be
detected 50 % of the time Subliminal perception
Below our level of awareness Extrasensory perception
Extraordinary perception such as sensing the future
2. Vision A. The Visual System
Cornea transparent protective coating over the front of the
eye Pupil
small opening in the iris through which light enters the eye
Iris colored part of the eye
Lens transparent structure inside the pupil that focuses
light onto the retina Retina
lining of the eye containing receptor cells that are sensitive to light
Retina Movie
The Visual System Visual System Movie
#1
Visual System Movie #2
Visual System Movie #3
Receptor cells Wavelengths - different energies represented in
the electromagnetic spectrum Rods - receptor cells in the retina for night vision Cones - receptor cells in the retina responsible for
color vision. Bipolar Cells - connect receptors to ganglion Fovea / visual acuity - area of the retina with the
sharpest vision Retina / Fovea Movie
Cones respond to light and dark as well as to color or different wavelengths of light
Adaptation Dark
Increased sensitivity of rods and cones in darkness
Light Decreased sensitivity of rods and cones in
bright light Afterimage
Sense experience that occurs after a visual stimulus has been removed
Eye to brain Neurons that connect the bipolar cells in the eyes
to the brain Optic nerve are bundle of axons of ganglion cells
that carries neural messages from each eye Blind spot
place where the axons of all the cells leave the retina (no receptors)
The bipolar cells connect to ganglion cells, whose axons converge to form the optic nerve that carries messages to the brain
B. Color Vision Properties of color
Hues – Colors such as red and green Saturation - Vividness of a hue Brightness - Nearness of a color to white
Theories of color vision Subtractive color
Mixing pigments Additive color mixing
Lights, T.V., monitor (RGB)
Trichromatic theory (Helmholtz) Colorblindness (Tri-,Di-, and
Monochromats) 3 different receptors (RGB) People inherit receptors which respond
differently
Opponent-process theory (Hering) Three sets of color receptors Yellow-blue, red-green, black-white Either/or response
C. Color Vision in Other Species
The opponent-process theory maintains that receptors are specialized to respond to either member of the three basic color pairs: red-green, yellow-blue, and black-white (dark and light)
3. Hearing A. Sound
Sound waves Changes in pressure caused by molecules of air
moving Frequency
Number of cycles per second in a wave; pitch Hertz
Cycles per second; frequency
Pitch Frequency of vibrations, results in tone
Amplitude Magnitude; loudness
Decibels Measurement of loudness
Overtones - Multiples of the basic tone Timbre - Quality of texture of sound
Amplitude is the magnitude of a wave; it largely determines the loudness of a sound. Loudness is measured in decibels
B. The Ear Hammer, anvil, stirrup
3 small bones in the middle ear that relay vibrations
Oval window Membrane between middle ear and inner ear
Hearing begins when sound waves strike the eardrum and cause it to vibrate. This vibration, in turn, makes three bones in the middle ear—the hammer, the anvil, and the stirrup—vibrate in sequence
Cochlea Part of inner ear containing fluid that vibrates
and then causes the basilar membrane to vibrate
Basilar membrane Vibrating membrane in the cochlea which
contains receptor cells Neural connections
Auditory nerve Connection from ear to brain Bilateral
Inside the organ of Corti are tiny hair cells that act as sensory receptors for hearing. Stimulation of these receptors produces auditory signals that are transmitted to the brain through the auditory nerve. The brain pools the information from thousands of these cells to create the perception of sounds
C. Theories of Hearing Place theory
Pitch is determined by location of vibration Frequency theory
Pitch is determined by frequency hair cells fire Volley Principle
Pattern of sequential firing determines pitch
Hearing disorders Damaged eardrum Damaged middle ear bones Damaged nerves Loud music, tools, etc Tinnitus 1% of population
4. The Other Senses A. Smell
Detecting common odors Communicating with pheromones
B. Taste Receptor cells in taste buds
The sense of smell is activated by substances carried by airborne molecules into the nasal cavities, where the substances activate highly specialized receptors for smell, located in the olfactory epithelium
The receptor cells for the sense of taste are housed in the taste buds on the tongue, which, in turn, are found in the papillae, the small bumps on the surface of the tongue
C. Kinesthetic and Vestibular Senses Stretch receptors
Sense muscle stretch and contraction Golgi tendon organs (injections)
Sense movement of tendons Vestibular senses
Senses of equilibrium and body position
D. Sensations of Motion Vestibular organs are also responsible for motion
sickness May be caused by discrepancies between visual
information and vestibular sensation E. The Skin Senses
Skin receptors for pressure, temperature, and pain Importance of touch
F. Pain Individual differences Gate control theory
Gate in spinal cord which controls transmission of pain to brain
Biopsychosocial theory The Placebo Effect Alternative approaches
5. Perception A. Perceptual Organization B. Perceptual Constancies
Size constancy Shape constancy Brightness constancy Color constancy
Perceptual Organization
Perceptual constancy is our tendency to perceive objects as unchanging in the face of changes in sensory stimulation. Once we have formed a stable perception of an object, we can recognize it from almost any angle
C. Perception of Distance and Depth Moon Movie
D. Perception of Movement E. Visual Illusions
When we use sensory information to create perceptions, we fill in the missing information, group various objects together, see whole objects, and hear meaningful sounds
Visual illusions occur when we use a variety of sensory cues to create perceptual experiences that do not actually exist
F. Observer Characteristics: Individual Differences and Culture Motivation Value Expectation Cognitive Style Experience and Culture Personality
Superposition is a monocular distance cue in which one object, by partly blocking a second, appears closer
Linear perspective is another monocular cue to distance and depth based on the fact that two parallel lines seem to come together at the horizon