Download Sensation & Perception

Sensation &
Perception
basic terminology
Sensation
Information coming into our brain from our sensory
receivers
Perception
The way the brain organizes and interprets the data
received by our senses
Can you have sensation without perception?
Prosopagnosia
Complete sensation in the absence of perception
Example of Prosopagnosia: FACE BLINDNESS
Bottom-up Processing
Analysis of the stimulus begins with the sense
receptors and works up to the level of the brain
and mind.
Letter “A” is really a black blotch broken down into
features by the brain that we perceive as an “A.”
Top-Down Processing
• Information processing guided by higher-level
mental processes as we construct
perceptions, drawing on our experience and
expectations.
• Top Down Processing explains how our
expectations and prior experiences guide our
perceptions.
THE CHT
Bottom Up Vs. Top Down
• What do you see?
Bottom Up vs. Top Down
What do You See?
Top-Down Processing
• Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it
deosn't mttaer in waht oredr the ltteers in a wrod
are, the olny iprmoetnt tihng is taht the frist and lsat
ltteer be at the rghit pclae. The rset can be a total
mses and you can sitll raed it wouthit a porbelm.
Tihs is bcuseae the huamn mnid deos not raed
ervey lteter by istlef, but the wrod as a wlohe.
Sensation vs. Perception
What do you see?
Sensation vs. Perception
What do you see?
Making Sense of Complexity
“The Forest Has Eyes,” Bev Doolittle
How many faces do you see?
Thresholds
Absolute Threshold
Minimum stimulation needed to detect a particular
stimulus 50% of the time.
•
Ticking of a watch from about 20ft away in a quiet
•
room
Seeing a candle flame 30 miles away on a clear night
–Go to your textbook p. 79 for the absolute threshold of taste and
touch.
Subliminal Messages
Messages presented below absolute thresholds –
not consciously perceived
“Subliminal Messages”
• Some have argued that humans still “pick up”
these messages that influence our
“unconscious.” Do these messages have
suggestive powers?
• Skeptics argue “Subliminal Messages” are
heavily influenced by top down processes.
• Example: Feeling “hungry” during subliminal
advertisements.
Mr. Subliminal
Subliminal Message In Beer Ad?
Subliminal Messages In Money
Subliminal Message In
“The Lion King?”
Difference Threshold
Amount of change needed to notice that a change
has occurred.
Sensation: Thresholds
• Signal Detection Theory: predicts how and
when we detect the presence of a faint stimulus
(signal) amid background stimulation (noise)
• Assumes that there is no single absolute
threshold
• What might a person’s detection of a
stimulus depend on?
Condensation Experiment
Sensory Adaptation
Sensory Adaptation
Diminished sensitivity as a consequence of
constant stimulation.
Put a band aid on your arm and after awhile
you don’t sense it.
The EYE
vision
The Eye
Biology of Vision: Know the Steps
1. Light enters the eye through the cornea:
(transparent protector) and passes through
the pupil: (small opening/hole).
2. The size of the opening (pupil) is regulated by
the iris: the colored portion of your eye that
controls the size of the pupil causing either
more or less light to get in.
Biology of Vision: Know the Steps
3. Behind the pupil, the lens, focuses the light rays into
an image on the back surface of the eye called the
retina: where the image is focused. The retina is like
a movie screen.
Biology of Vision: Know the Steps
4. Image coming through activates photoreceptors in
the retina called rods and cones (process
information for darkness and color).
5. The rods and cones set off chemical reactions they
form a synapse with bipolar cells which change light
energy into neural impulses.
6. These neural impulses go to the optic nerve
(bundle of neurons that take information from retina
to the brain) and eventually get to the visual cortex in
the occipital lobe.
Opponent Process Theory
Gaze at the middle of the flag.
When it disappears, stare at the dot and report
whether or not you see Britain's flag.
What just happened is called a NEGATIVE AFTERIMAGE
Opponent Process Theory
• The opponent color theory suggests that there
are three opponent channels: red versus green,
blue versus yellow, and black versus white (the
last type is achromatic and detects light-dark
variation, or luminance.
• Trichromatic Theory of Color Vision:
This theory states that three receptors in the retina of the
eye are responsible for the perception of color by the brain.
Each receptor is sensitive to a single color: red, green or
blue. The combination of these three colors can form
any visible color in the spectrum.
Which one of the
Theories of color vision creates
The afterimage effect?
What is transduction?
• Transduction is the process by which our
sensory systems convert stimulus energy into
neural messages.
• In the eye: happens in the optic nerve
• In the ear: happens in cochlea and auditory
nerve.
Weber’s Law
• Weber’s Law is the perception of two
different stimuli that are different by a
constant minimum percentage.
• Example: Difference between 2 notes on a
scale.
• The difference has to be constant and by a
set percentage in order for there to be
adequate perception of the difference.