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