Sensation and Perception
Psychology
Sensation
• The process of detecting a physical stimulus:
» Vision (light waves)
» Touch (movement of /pressure)
» Hearing (sound waves)
» Taste (chemical substances)
» Smell (chemical substances)
» Pain (unique)
Psychophysics
• A specialty area of psych. that studies sensory
limits, sensory adaptation, and related topics.
Transduction
• Sensory pathway –
Bundles of neurons that carry information
from the sense organs to the brain.
• sights, sounds, and smells are converted to
neural impulses that our brain can interpret.
Doctrine of Specific Energies
• Nervous system encodes sensory messages by
ANATOMICAL CODE (uses parts of the body).
• Theory works for vision, hearing, and taste.
How sensitive are we to changing
stimulation?
• Absolute threshold: the smallest quantity of
physical energy that can be reliably detected
by an observer.
• Absolute threshold works at least 50 percent
of the time.
• *People differ in their A.T.
Official List Galanter, 1962
• List is on page 151 in your textbook
Homework: copy the list into to your notes!
Difference threshold (jnd):
– Just Noticeable Difference
– Definition: The smallest difference in stimulation
that can be detected by an observer when two
stimuli are compared. And the ability to notice a
difference when the amount of a single stimuli
increases or decreases.
Perception
• The process by which the brain organizes and
interprets sensory information, transforming
it into meaningful objects and events.
Perception
Perception
Perception
Difference B/W Sensation and
Perception
• Sensation =
Eating a red grape is
Sensation.
Taste receptors in your
mouth which then
sends the info. To the
parietal lobes.
• Perception =
Remembering that you
love the taste of red
grapes is Perception.
“wow this grape is
sweet..”
Selective attention
• we can only focus awareness on a limited part
of what we are sensing.
Ex. At a party
Ex. cafeteria
Cocktail party effect
• – type of selective attention in which you can
attend to only one voice/visual at a time.
Sensory Adaptation
• Sensory adaptation –
Loss of responsiveness in receptor cells after
stimulation has remained unchanged for a
while
Sensory Deprivation
• The absence of normal levels of sensory
stimulation.
• Read study on page 154
Learning Targets
• Compare three forms of visual detection.
Judge the effectiveness of psychophysics
technology to aid in human visual detection.
• 1. Signal Detection Theory
• 2. Echolocation
• 3. Connecting computers to the visual cortex
Signal-Detection Theory
• The belief that the ability to detect a signal
varies with the characteristics of the perceiver,
the background, and the stimulus itself.
Signal Detection Theory
Stimulus is Present
Stimulus is Absent
Response:
“Present”
Hit
False Alarm
Response:
“Absent”
Miss
Correct Rejection
S-D theory
• Physical condition can affect detection of a
signal
• Psychological factors i.e., attention level and
states of motivation can affect detection of a
signal
Process
1.Stimulus event
2.Neural activity
3.Comparisons with personal standard
4. Action (or no action)
Practical examples of S-D Theory
• Walking down a darkened street by yourself
late at night, you may be especially attentive
to even the slightest sounds b/c they signal
danger. Fail to notice the same sounds in
broad daylight.