Transcript Sensation - Ionia Public Schools

Module 11
Introduction to
Sensation and
Perception
Sensation
 Sensation
 the process by which our sensory
receptors and nervous system receive
and represent stimulus energy
 Perception
 the process of organizing and
interpreting sensory information,
enabling us to recognize meaningful
objects and events
Sensation
 Sensation
how do we change energy into sense
 Perception
what do we do with our sensory
information
Sensation
 Our
sensory
and
perceptual
processes
work
together to
help us
sort out
complex
images
Sensation
 Bottom-Up Processing
 analysis that begins with the sense receptors
and works up to the brain’s integration of
sensory information (piecing lines together to
recognize the number 4)
 Top-Down Processing
 information processing guided by higher-level
mental processes
 as when we construct perceptions drawing on
our experience and expectations (think you
know someone and as they get closer, realize that
you don’t)
Sensation- Basic
Principles
 Psychophysics
 study of the relationship between
physical characteristics of stimuli and
our psychological experience of them
 Light- brightness
 Sound- volume
 Pressure- weight
 Taste- sweetness
SensationThresholds
 Absolute Threshold
 minimum stimulation needed to detect a
particular stimulus 50% of the time
 isn’t constant – can change with motivation
and alertness
 Difference Threshold
 minimum difference between two stimuli
required for detection 50% of the time
 just noticeable difference (JND)
Sensation- A. 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
 detection depends partly on person’s
 experience
 expectations
 motivation
 level of fatigue
Sensation- A. Thresholds
 Signal Detection Theory
detection of stimuli involves decision
processes as well as sensory processes
Example – riddle, shower/telephone
“You’re driving a bus with 12 passengers. At your
first stop, 6 passengers get off. At the second
stop, 3 get off. At the third stop, 2 more get off,
but 3 new people get on. What color are the
driver’s eyes?
Did you detect the signal – who is the driver? –
over the noise – number of passengers?
Sensation- A. Thresholds
100
Percentage
of correct
detections
 Subliminal
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
 when stimuli are
below one’s
absolute
threshold for
conscious
awareness
Sensation- A. Thresholds
Subliminal Messages
Reverse Speech - Voices From The
Unconscious
Sensation- Thresholds
 Difference Threshold
 minimum difference between two stimuli
required for detection 50% of the time
 just noticeable difference (JND) – we
experience the difference threshold as a JND.
 Read the passage at
the right.
 How many lines do
you require to
experience a
noticeable difference?
Sensation- D. Thresholds
 Weber’s Law
 to be perceived as different, two
stimuli must differ by a constant
minimum percentage (rather than a
constant amount)
 light intensity- 8% (1/60)
 weight- 2% (1/50)
 tone frequency- 0.3% (1/333)
Sensation- D. Thresholds
 Sensory Adaptation
 diminished sensitivity as a
consequence of constant stimulation
(wearing a new wristwatch)
 Selective Attention
 focusing of conscious awareness on a
particular stimulus
 as in the cocktail party effect (listen to
one voice, among many)
Now you see it,
now you don’t!
Perception
 Selective Attention
Do you see circles
with white lines or
a cube?
Because attention is
selective, you only
see one
interpretation at a
time.
Change Blindness
 Change Blindness is an example of
Selective Attention
Lab Demos
Change Blindness