Transcript Un 1 Sensation and Perception Notes

Psych 11
WEARENOWHERE
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knowledge of the world depends on: vision,
hearing, taste, smell, position, movement,
balance, and touch
eyes and ears pick up stimuli such as light and
sound waves and send neural signals to the
brain
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sensation = physical energy from objects in
the world or in the body stimulates the sense
organs
Perception = happens when the brain
organizes and interprets sensory information
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Cutting yourself example – it is in you, and you
will remember the pain when you see the knife
(near you, near others-same neurons stimulated,
evidence of learning, genetic predisposition of
neurons to connect – visual to pain receptors)
Histamine
Pain sensations are processed and altered by
mechanisms within the spinal cord.
 Endorphins relieve pain by inhibiting pain perception
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Gate-control theory -pain signals traveling
from the body to the brain must go through a
gate in the spinal cord
If the gate is closed, pain signals can’t reach
the brain
-not really a gate -a pattern of neural activity
that either stops pain signals or allows them
to pass
Signals from the brain can open or shut the
gate
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The neural pathways for emotional and
physical pain cross
The brain cannot distinguish
Pain can be controlled by a number of
therapies including, drugs, surgery,
acupuncture, exercise, hypnosis, and even
thought distraction.
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Transduction
 Sensory organs contain receptors that transduce
sensory energy into nerve impulses that are
carried to the brain
External light falls on receptors within the
eye to generate the visual message
Light = electromagnetic radiation
Wavelength of light determines color
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Accommodation refers to automatic
adjustments of the eye, which occurs when
muscles change the shape of the lens so that
it focuses light on the retina from objects at
different distances.
 Nearsightedness
 Farsightedness
Three Types of Processing:
1.
Transduction: converts sensory stimuli into
neural impulses that are sent on to the brain
2.
Sensory Reduction: filters and analyzes
incoming sensations before sending on to the
brain
3.
Coding: converts particular sensory input into a
specific sensation sent to differing parts of the
brain
Humans are able to discriminate
7 million different hues
Colors convey important
information:
Ripeness of food
Danger signals
Trichromatic theory
Eye contains 3 different color
sensitive elements
Blue, green or red elements
Trichromatic theory accounts for
color mixing of lights.
Optic nerves connect to the thalamus in the
middle of the brain, and the thalamus connects
to the visual cortex
Genetic disorder in which people are blind to
green or red colors. This supports the
Trichromatic theory.
Ishihara Test
Gaze at the middle of the flag for about 30
Seconds. When it disappears, stare at the dot and report
whether or not you see Britain's flag.
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Psychophysics is the study of how the
physical properties of stimuli relate to
people’s experience of stimuli
 Questions the acuity of the senses
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Close your left eye, and fixate your right eye on the
black dot. Move the page towards your eye and away
from your eye. At some point the car on the right will
disappear due to a blind spot
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Psychologists assess the acuity of the senses
in three ways:
 Measuring the absolute threshold
 Measuring the difference threshold
 Applying signal detection theory
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The absolute threshold is the minimum
amount of stimulation required for a person
to detect the stimulus 50 percent of the time
difference threshold is the smallest
difference in stimulation that can be detected
50 percent of the time-just noticeable
difference (jnd), depends on the strength of
the stimulus.
Activation of retinal cells by light results in action
potentials that travel along neurons that project to
the occipital cortex
Wavelength (distance between peaks)
- determines frequency
- perceived as pitch
- some wavelengths cannot be perceived
Amplitude (height of wave)
- perceived as loudness
Mixture of Wavelengths; Complex Sounds
- perceived as timbre / tone saturation
Cochlea: Coiled, bony, fluidfilled tube in the inner ear that
transforms sound vibrations to
auditory signals.
Place Theory of Pitch Perception
 location of stimulation is important
 only explains perception of high frequencies
Frequency Theory of Pitch Perception
 frequency of nerve firing
▪ limitations of neuronal firing rate
 volley principle
▪ cell clusters can exceed limitations of firing rate
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Receptors are embedded in a mucus-coated
membrane called the olfactory epithelium
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When chemical molecules in the air pass
through the nose, the receptors initiate a
neural impulse which travels to the olfactory
bulb, where most olfactory information is
interpreted
=Olfaction
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The sense of smell is closely connected with
memory
Most people have had the experience of
smelling something, maybe a certain perfume or
spice, and suddenly experiencing a strong
emotional memory
Researchers don’t know exactly why this
happens, but they theorize that smell and
memory trigger each other because they are
processed in neighboring regions of the brain.
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Taste receptors are located on the tongue
and are sensitive to five major tastes: salty,
sweet, sour, bitter and umami.
Taste receptors respond differentially to the
varying shapes of food and liquid molecules.
=Gustation
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The sense of touch is a mix of four distinct
skin senses—pressure, warmth, cold, and
pain.
Skin Senses: there are three basic skin sensations:
touch, temperature, and pain.
 Vestibular Sense: sense of body orientation with
respect to gravity and three-dimensional space
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 The semicircular canals provide the brain with balance information.
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Kinesthetic Sense: sensory system for body
posture, orientation and movement
 Kinsethetic receptors are found throughout the muscles, joints, and
tendons of the body.
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Perceptual processes include:
 Selection refers to choosing which of many stimuli that
will be processed.
 Organization involves collecting the information into
some pattern.
 Interpretation involves understanding the pattern
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Selective attention: filtering out and
attending only to important sensory
messages.
Feature detectors: specialized cells in the
brain that respond only to certain sensory
information
Habituation: tendency of the brain to ignore
environmental factors that remain const
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Gestaltists proposed laws of organization
that specify how people perceive form.
Figure and ground are basic organizational
themes for perception.
 Figure is perceived as distinct from the
background.
 Figure is closer to the viewer than the
background.
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Perceptual Constancy is the tendency for the
environment to be perceived as remaining
the same even with changes in sensory input.
 Size constancy
 Shape constancy
 Color constancy
 Brightness constancy
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Depth perception is the ability to perceive
three-dimensional space and to accurately
judge distance.
Binocular cues include retinal disparity and
convergence. (fingers in, 1inch-5inch)
Monocular cues include linear perspective,
interposition, relative size, texture gradient,
aerial perspective, light and shadow,
accommodation and motion parallax.
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Interpretation is influenced by:
perceptual adaptation
perceptual set
individual motivation
frame of reference
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Subliminal stimuli are stimuli presented
below the threshold of awareness; the effect
on behavior is uncertain
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ESP refers to the ability to perceive stimuli
that are outside the 5 senses
 Telepathy: the ability to read minds
 Clairvoyance: the ability to perceive objects or
events
 Precognition: the ability to predict the future
 Psychokinesis: the ability to move objects