sensation and perception
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Sensation and Perception. Sensation: your window to the world Perception: interpreting what comes in your window. Sensation. Sensation - The passive process of receiving and detecting a stimulus by the nervous system. - PowerPoint PPT PresentationTRANSCRIPT
Sensation and Perception
Sensation: your window to the world Perception: interpreting what comes
in your window.
Sensation
• Sensation - The passive process of receiving and detecting a stimulus by the nervous system.
• Process of sensing our environment through taste, sight, sound, touch and smell
• Example: Hearing Mrs. Joseph speak, the sound waves travel to the ears. The hair on the cells in the cochlea help transmit the information to the brain
Perception• Perception - The active process of
selecting, organizing, and interpreting the information brought to the brain by the senses
• Perception is the way we interpret sensations and therefore make sense of everything around us
• Based on our prior experiences and expectations
• Example:– Seeing letters on a page and
interpreting them as our favorite passage in a novel
Bottoms-up Processing• Bottoms Up Processing (AKA -
Feature analysis)• Begins with the sensory
receptors and works its way up to the brain
• Use the features of the object itself to process the information
• Examples: – seeing the individual fruits in this
picture– Hearing a voice speak about AP
Psych
Top Down Processing• Top Down Processing - Processing
information from the senses with higher level mental processes using our experiences and expectations
• Using your background knowledge to fill in the gaps
• Examples: – Seeing the face in the picture made up of fruit– I _ope yo_ get an 5 on t_ _ A _e_am– Negative expectations about the pain of
childbirth can increase pain during the birthing process
• Find the following hidden items:
• Scissors• Banana• Screwdriver• Horn • Heart• fish • boat • Shoe• needle
• Aoccdrnig to a rscheearch at an Elingsh uinervtisy, it deosn’t mttaer in what oredr the ltteers in a word are, th olny iprmoetnt tihng is that frist and lsat ltteer is at the rghit pclae. The rset can be a toatl mses and youcan still raed it wouthit a porbelm. This is bcuseae we do not raed erveylteter by it slef but the word as a wlohe.
Selective Attention
• Selective Attention - Ability to focus our conscious awareness on a particular stimulus
• Example: Cell phone usage while driving a car
Selective AttentionExample
The Stoop Effect
• Stroop Effect - Demonstrates the nature of automatic processing versus conscious visual control. The difficulty you had reading it was due to semantic interference
Cocktail-party phenomenon• cocktail party effect -
ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations.
• Form of selective attention.• Example:
– You are at the football game and are cheering for the Comets when you hear Ms. Short call your name
Selective Inattention • Change Blindness/Inattentional
Blindness - Falling to notice changes in the environment– Example: Eating your lunch in the cafeteria, when
your friend switches your sandwich and you don’t notice
– Choice Blindness - failure to notice a switch in a choice that is made
• Example: Participants asked to pick between two photographed faces, when photographs are switched…
– Change deafness – failure to notice a change in voices that are speaking
• Example: Listening to Mrs. Joseph speak, failure to notice that Mrs. Harvey is now speaking
Create your own examplesPick two that you are having the most difficulty with and make your partner
come up with a new example• Sensation• Perception• Bottoms-up processing• Tops-down processing• Selective Attention• Stroop Effect• Cocktail Party effect• Inattentional Blindness• Choice Blindness• Change Deafness
No stinky examples!
Pop Out Effect
• Pop out – stimuli we don’t chose to attend to but they draw our eyes and demand our attention
• Example: Picture on the left
Complete sensation in the absence of complete perception is best illustrated
by
Weber’s
Law
Proso
pagnosia
Conduction dea...
Color consta
nc...
Senso
ry inte
ra...
0% 0% 0%0%0%
1. Weber’s Law2. Prosopagnosia3. Conduction
deafness4. Color constancy5. Sensory interaction
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The process by which we select, organize, and interpret sensory information in order to recognize meaningful
objects and events is called
Senso
ry adapta...
Paralle
l pro
ce...
Sensa
tion
Perception
accomodation
0% 0% 0%0%0%
1. Sensory adaptation2. Parallel processing3. Sensation4. Perception5. accomodation
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Patients' negative expectations about the outcome of a surgical procedure can increase their postoperative experience of pain.
This best illustrates the importance of
Transducti
on
Accomodati
on
Senso
ry adapta...
Diff
erence
thr..
.
Top down proce
...
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1. Transduction2. Accomodation3. Sensory adaptation4. Difference
thresholds5. Top down
processing
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Researchers found that 40% of people focused on repeating a list of challenging words, failed to notice a
change in the person speaking. This illustrates
Top Down Proce
...
Bottoms up Pro
...
The Diff
erence
...
Change Deafnes..
.
Perception
20% 20% 20%20%20%1. Top Down Processing2. Bottoms up Processing3. The Difference
Threshold4. Change Deafness5. Perception
You typically fail to consciously perceive that your own nose is in you line of vision. This illustrates
Sublim
inal per..
.
Change blindne...
Perception
Selecti
ve Atte...
The cock
tail p...
20% 20% 20%20%20%1. Subliminal perception
2. Change blindness3. Perception4. Selective Attention5. The cocktail party
effect
Psychophysics
• Psychophysics - Study of how physical stimuli are translated into psychological experience.
• Psychologists use thresholds to measure these events
• Example: Tracking a person’s eye movements jumping every .33 of a second
Thresholds• Threshold – the point at which a sensory
information is strong enough to be noticed
• Absolute threshold – The smallest amount of a sensory stimulus needed to notice that the stimulus is there at all
• Examples: Light A candle flame at 30 miles on a dark, clear night.
Sound The tick of a mechanical watch under quiet conditions at 20 feet.
Taste One teaspoon of sugar in two gallons of water.
Smell One drop of perfume diffused into the entire volume of a three-bedroom apartment.
Touch The wing of a bee falling on your cheek from a distance of one centimeter.
Signal Detection Theory• Signal Detection Theory -
Predicts how and when we detect a signal amid background noise
• Assumes no absolute threshold
• Detection depends partly on a person’s experience, expectations , motivation and alertness…people respond differently to same stimuli
• Example: Enemy submarine,• Waiting for the Pizza man to
come at a busy party
Subliminal Stimulation
• Subliminal – below one’s absolute threshold for conscious awareness
• Example: – Listening to tapes in your to get you
to lose weight
• Priming – increased sensitivity to certain stimuli due to prior experience outside conscious awareness– Example: Seeing a picture of a mouse
before viewing the picture on the left
Do Subliminal Messages work?• Based on studies, some people
do respond to stimuli below the absolute threshold, under some circumstances. – People behave differently at
different threshold levels– Priming can briefly influence
preferences or perceptions– Complex behaviors are NOT
influenced by subliminal messages
– Some people are more suggestible than others
– Placebo effect
0
25
50
75
100
LowAbsolutethreshold
Medium
Intensity of stimulus
Percentageof correctdetections Subliminal
stimuli
Subliminal messaging vs. Priming
• Why the difference between priming studies and subliminal message studies?– priming: immediate, short-term effect on
simple judgments and actions– subliminal messages: aim for long-term
effects on consumer purchases, voter sentiment, or even suicide – most studies not proven to provide long term effects
Difference ThresholdDifference Threshold (AKA Just
Noticeable Difference) – the amount a change needed in a stimulus (stronger or weaker) for us to recognize the change has occurred
• the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change.
• Example:– Some people are better at detecting slight
variations in the taste of pop
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Just noticeable difference
Weber’s Law
• Weber’s Law (Related to JND) - For people to really perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount".
• Proportion varies depending on the stimulus
Weber’s Law• JND
– Pitch = .003 ( if someone sings a little off key, we will be able to tell)
– Loudness = .10– Saltiness = .20– Light = .08
• Example:– JND for a 10oz weight = 1 oz. To notice a 50 oz
weight would be 5oz– JND for a 10 decibel sound = .10 decibels . To
notice a sound of 30 decibels would be _______?
Sensory Adaptation
• Sensory Adaption - Diminished sensitivity as a consequence of constant stimulation
• Example:Jumping into a cold swimming pool, doesn’t feel cold after a while
Your eyes when you turn off the lights
Do you feel your underwear all day?
After listening to the television for 10 minutes, you fail to notice how loud the
volume is. This is an example of
Weber’s
Law
Habitu
ation
Senso
ry adapta...
Just
noticeab
l...
Absolute
thre
s...
0% 0% 0%0%0%
1. Weber’s Law2. Habituation3. Sensory adaptation4. Just noticeable
difference5. Absolute threshold
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Which theory emphasizes that personal expectations and motivations influence the level
of absolute thresholds?
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1. Signal detection theory
2. Just noticeable difference
3. Weber’s law4. Bottoms-up theory5. Tops-down theory1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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The minimum amount of stimulation a person needs to detect a stimulus 50 percent of the time is called the
Adaptation th
r...
Diff
erence
thr..
.
Absolute
thre
s...
Sublim
inal thr..
.
Change thre
sho...
0% 0% 0%0%0%
1. Adaptation threshold
2. Difference threshold3. Absolute threshold4. Subliminal threshold5. Change threshold
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A subliminal message is one that is presented
while
an individual is
u...
below one's abso
lute th
...
in a m
anner that is
unco...
with
very so
ft backgro
u..
Repetitiously
0% 0% 0%0%0%
1. while an individual is under hypnosis.
2. below one's absolute threshold for awareness.
3. in a manner that is unconsciously persuasive.
4. with very soft background music.
5. Repetitiously1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
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