Transcript Module 9 & 10

Module 9 & 10
Sensation and
Perception
ThEcOwgAvecOla.
The cow gave cola
.rat eht saw tac ehT
The cat saw the rat.
The cat was the rat.
Absolute Thresholds
• The level of sensory stimulation necessary for
sensation to occur.
– Vision: Candle flame seen at 30 miles on a clear
night.
– Hearing: Tick of a watch under quiet conditions at
20 feet
– Touch: A bee’s wing falling on you cheek from 1
centimeter (.4 inch) above.
– Smell: 1 drop of perfume diffused into a three
room apartment
– Taste: 1 teaspoon of sugar in 2 gallons of water.
Difference Threshold
• The minimum difference that a person
can detect between two stimuli.
• Just noticeable difference
Signal Detection Theory
• Set of formulas and principles that predict when
we will detect the presence of a faint stimulus
amid background stimulation.
– Detection depends on qualities of the stimulus, the
environment, and the person who is detecting.
• Three Variables:
– Stimulus Variable: how bright is the blip on the radar
screen
– Environmental Variables: how much distracting noise is
there in the room with the radar equipment
– Organismic Variables: is the operator properly trained and
motivated.
Sensory Adaptation
Diminished sensitivity as a result of
constant simulation.
Selective Attention
Focusing conscious awareness on a
particular stimulus to the exclusion of
others.
Sensation
The process of receiving information
from the environment.
Vision
• Dominates human senses.
• Light
– White Light: light as it originates from the sun or a
bulb before it is broken into different frequencies.
– Color is seen because light bounces off objects at
different frequencies.
– The eye has different receptors for different wave
lengths.
– Wave lengths are based on the texture and
solidity of what they hit.
Electromagnetic Energy
• An energy spectrum that includes X-rays, radar, and
radio waves, among other things. A small portion of
this spectrum includes visible light energy, which can
be detected by the eye.
• Two Characteristics Determines What We See:
– Length of the wave determines color
• Hue: The color of light, determined by the wavelength
of light energy
– Amplitude of the wave (height) determines
brightness
• Taller is brighter.
Parts of the Eye
• Cornea: clear outer covering of the eye,
behind which is a fluid.
• Iris: a colored circular muscle that
opens and closes, forming larger and
smaller circles to control the amount of
light getting into the eye.
• Lens: the part of the eye that focuses
an image on the retina.
Parts of the Eye
• Pupil: The opening in the eye.
– Psychological factors that control iris muscles.
• Smaller when disgusted
• Larger when
– Really like something or someone
– Afraid
– Strong emotional arousal
• Retina: Back of the eye, which contains
millions of receptors for light.
Parts of the Eye
• Rods: A visual receptor most sensitive to
violet-purple wave length; very sensitive for
night vision; “sees” only black and white.
• Cones: a visual receptor that responds
during daylight; “”sees” color.
– Red range
• Rods are on the side and cones in the middle
of the retina.
Differences Between the Cone
and Rod Receptors
Cones
• Number 6 million
• Location in Retina Center
– (fovea)
• Color Sensitive? Yes
• Low sensitivity I dim light
• High ability to detect
sharp detail (acuity)
Rods
• Number 120 million
• Location in Retina Edge
– (periphery)
• See Black and white
• Highly sensitive to dim
light
• Low ability to detect
sharp detail (acuity)
Rods and Cones
• Bipolar Cells: cells that form the middle layer in the
retina. Bipolar cells gather information from the rods and
cones and pass it on to the ganglion cells.
• Ganglion Cells: the top layer in the retina. Ganglion
cells receive information from the bipolar cells and
transmit it through their axon, which together form the
optic nerve.
• Optic Nerve: the nerve that carries visual information
from the eye to the occipital lobes of the brain.
– Blind Spot: the point at which the optic nerve travels
through the retina to exit the eye. The lack of receptor rods
and cones at this point creates a small blind spot.
Color Blindness
• Inability to perceive certain colors, such
as red and green.
– 8% Males
– .05 % Females
• Red and Green cones do not work
• Truly color blind people are very rare
Afterimage
• Image that remains after stimulation of
the retina has ended. Cones not used
fire to bring the visual system back in
balance.
Hearing
Audition: the sense of hearing.
Characteristics of Sound
•
•
•
•
Pitch: How high or low a sound is
Timbre: the complexity of a sound
Intensity: how loud a sound is
Decibels: a measure of how loud a
sound is (its intensity)
The Structure of the Ear
• Eardrum: a piece of skin stretched over the
entrance to the ear; vibrates sound
• Cochlea: A snail-shaped part of the ear, filled
with fluid and small hairs that vibrate to
incoming sound
• Hair-cells: receptor cells for hearing found in
the cochlea
• Cilia: Hairlike extensions on cells
• Auditory nerve: bundle of nerves carrying
sound to the brain
Hearing
• Sound waves go to the eardrum where
vibration is started. This vibration causes the
cochlea to vibrate where cilia are located.
Cilia are tuned to receive different frequency
movements of hair that cause electrical
impulses to go through the auditory nerve to
the brain.
• How strong and when a sound arrives at one
ear is contrasted by the brain with the same
thing from the other ear. Differences help us
locate where sound is coming from
Cutaneous Senses
( Touch)
• Cutaneous Receptors: Nerve receptors in
the skin that respond to pressure,
temperature, or pain
– Records pressure
– Changes in temperature
– Remain active continuously to record an injury or
poison
– Can fire for hours and hours after accidents
Smell
• Olfaction: the sense of smell
• Odor is hard to explain in words but when
associated with emotional events. We never
forget it.
• Odor can recreate strong emotional
memories.
• Olfactory Bulb: units that receive odor
molecules and communicate their nature to
the brain
Smell
• Cilia in the nose collect molecules of odor
which send an electrical impulse to the
olfactory bulb which generates a “code” that
is sent to the brain for interpretation.
• Smell is most critical in eating. More than
taste
• Pheromones: odor chemicals that
communicate a message
– Animals have them. Not sure if humans do.
Taste
• Taste receptors: chemical receptors on the
tongue that decode molecules of food or
drinks to identify them
• Types
–
–
–
–
Salt
Sweet
Sour
Bitter
• Work the same as cones
Salt
• Necessary for survival
– Operates nerve cells
– Keeps body chemistry in balance
– Used for muscle contraction
• Children crave salt and it tampers with
age until really old it re-opens
Sugar
(sweet)
• Necessary for energy
• Newborns can taste at one day old
• Too little sugar makes a person tremble,
feel faint, and causes mental confusion
• The desire for something sweet is built
in
Sourness and Bitterness
Detectors
• Bitterness - Poisons - no odor
• Sourness - Food gone bad - odor
Body Senses
• Kinesthetic sense: the system for
sensing the position and movement of
individual body parts.
• Vestibular sense: the system for
sensing body orientation and balance,
located in semicircular canals of the
inner ear.
Perception
What do you see?
Perception
• The process of organizing and interpreting
sensory information
– Bottom-up process: Information processing
that focuses on the raw material entering
through our eyes, ears, and other organs of
sensation.
– Top-up Process: Information processing that
focuses on other expectations and experiences
in interpreting incoming sensory information
Gestalt
The “whole,” or the organizational
patterns, that we tend to perceive.
The Gestalt psychologists emphasized
that the whole is greater than the sum
of its parts.
Figure-Ground
Relationships
• Figure-ground: the organization of the
visual field into objects that stand out
from their surroundings.
Grouping Principles:
the perceptual tendency to organize stimuli into
understandable groups
• Similarity: a perceptual cue that involves grouping
like things together
• Proximity: a perceptual cue that involves grouping
together things that are near one another
• Closure: the process of filling in the missing details
of what is viewed
• Continuity: Once an object appears to move in a
particular direction, your brain assumes that
movement continues unchanged.
Depth Perception
The ability to see in three dimensions
and judge distance
Example:
• Visual Cliff: an apparatus used to demonstrate depth
perception
Binocular Depth Cues:
depth cues that require the use of both eyes
• Retinal Disparity: The difference
between the image provided by the two
retinas
– When the images are brought together in the brain, they
provide the sense of depth
• Convergence: the tension in the eye
muscles when the eyes track inward to
focus on objects close to the viewer
– Short distance
Monocular Depth Cues:
Depth cues that require the use of only one eye
• Relative Size: If an object of known size
appears large, it is probably close, and if an
object appears small, it is probably distant
• Relative Motion: Apparent slowness indicates
an object is distant
• Interposition: Closer objects partially obstruct
the view of more distant objects
• Relative Height: distant objects appear higher
in your field of vision that closer objects do
Monocular Depth Cues
• Texture Gradient: how rough or smooth
objects appear
– Gradient: Different level of textures we can see at
different distances
• Relative Clarity: Distant objects are
less clear than near by objects are
• Linear Perspective: Parallel lines seem
to draw together in the distance
Perceptual Constancies:
perceiving the size, shape , and lightness of an object as
unchanging, even as the retinal image of the object changes.
• Size Constancy: the ability to retain the size
of an object regardless of where it is located.
• Shape Constancy: The ability to perceive an
object as having the same shape regardless
of the angle at which it is seen
• Lightness Constancy: The ability to see an
object as having a constant level of lightness
no matter how the lighting conditions change
Perceptual Set
A mental predisposition to perceive
something one way and not another
Schemas: concepts or mental frameworks that
organize and interpret information
Context
The setting or environment in which
we interpret sensory stimuli
Illusions
In accurate perception