AP PSYCHOLOGY: UNIT IV How we construct representations of the external world.
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Transcript of AP PSYCHOLOGY: UNIT IV How we construct representations of the external world.
AP PSYCHOLOGY: UNIT IVHow we construct representations of
the external world
PART ONE
Sensation & Perception: The Basics
Sensation & Perception: Basics
Sensation The process by which our sensory receptors
and nervous system receive stimulus energies (information) from our environment
Stimulus – detectable input from environment Light – vision Sound – hearing Chemicals – taste and smell Pressure, temperature, pain – touch Orientation, balance – kinesthetic senses
Sensation & Perception: Basics
Sensory processes are the initial steps to perception: Transduction
Process of converting energy of stimulus into neural activityPhysical energy Neural signals
Adaptation Impacts transduction Constant level of stimulus results in decreased
response over timeBoth perceptual and sensory
Sensation & Perception: Basics
PerceptionThe process of
selecting and identifying information from the environment Organizing and interpreting sensory information so we can identify its meaning
One continuous process…
“The Forest Has Eyes”
• Bottom-up processing: • Identifying a stimulus by analyzing the
information available in the external stimulus
• Top-down processing:• Identifying a stimulus by using the knowledge we
already possess about the situation – based on expectations or past experiences
“The Forest Has Eyes”
(Bev Doolittle)
Sensation & Perception: Basics
Bottom-Up ProcessingAnalysis that begins with
sensory receptors and works up to the brain’s integration of sensory information Focuses on the stimuli entering through our eyes, ears and other senses
Sensation & Perception: Basics
Top-Down Processing Information-processing guided by
higher-level mental processes; when we construct perceptions by drawing on our experience and expectations
Top-Down Processing
We perceive by filling the gaps in what we sense. I _ant ch_co_ate ic_
cr_am.
Based on our experiences and schemas. If you see many old men
in glasses, you are more apt to process a picture of an old man (even when you may be in error).
Sensation & Perception: Basics
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 in 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.
What if we could sense everything?
Life would be overwhelming• So we can only take in a
window of what is out there.
Psychophysics: • Relationship between
physical characteristics of stimuli and our psychological experiences of them.
Sensation & Perception:Thresholds
PART TWO
• What stimuli cross our threshold for conscious awareness?
• Could you be influenced by stimuli too weak to be perceived?
• Why are we unaware of unchanging stimuli, like a band-aid on our skin?
Sensation & Perception: Thresholds
PsychophysicsA study of the relationship between the
physical characteristics of stimuli & our psychological experience with them In other words, how are physical stimuli translate into a psychological experience?
Physical World Psychological World
Light BrightnessSound Volume
Pressure Weight Sugar Sweet
Sensation & Perception: Thresholds
Absolute Threshold The minimum stimulation needed to detect a
particular stimulus 50 percent of the time The dimmest visible star The softest sound
No YesYesNo No
Observer’s Response
Sensation & Perception: Thresholds
Sense Absolute Threshold
Vision A candle flame seen from 30 miles away on a clear, dark night
Hearing The tick of a watch at 20 feet in very quiet conditions
Taste One teaspoon of sugar in two gallons of water
Smell One drop of perfume throughout a three-room apartment
Touch A bee’s wing falling on your cheek from a height of about 1 cm
Sensation & Perception: Thresholds
Will you be able to detect a weak stimulus?
Signal Detection Theory Predicts how and when we detect the presence
of a faint stimulus (“signal”) amid background stimulation Assumes that there is NO single absolute
threshold and that detection depends on several factors…Person’s experienceExpectationsMotivationsLevel of fatigue
Sensation & Perception: Thresholds
Difference Threshold Just Noticeable Difference The minimum difference between two stimuli
required for detection 50 percent of the time How much does the volume have to increase before
you can tell that your music has gotten louder? How much do you have to
loosen your shoelaces for them to feel slightly less tight?
NoObserver’s Response
No Yes
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
Sensation & Perception: Thresholds
Weber’s Law (Ernest Weber) The principle that two stimuli must differ by a
constant proportion for difference to be noticeable Ratio based on original stimulus, rather than a
constant amount
Example If you go from 1 to 2 (JND), then you must go
from 2 to 4 and then 3 to 6 to notice the same difference; a FIXED RATIO! How much sweetener does it take to notice a
difference in the sweetness of sweet tea? • DEPENDS ON THE INITIAL SWEETNESS
Weber’s Law In Practice● If you make $5 an hour a 50 cent hour
raise will be noticeable.● But at $10 an hour you may need $1 to
really realize a difference.
● The average person can perceive differences when:
●Light intensifies by 8%●Weight increases by 2%●Frequency of tone differs by 0.3%
Sensation & Perception: Thresholds
Fechner’s Law (Gustav Fechner) Continuous increases in physical energy will
result in smaller increases in perceived magnitude; not a true ratio! Slight adjustment to Weber’s Law
Eventually we reach a place where physical energy starts to level off and we no longer notice a difference
Lower and upper thresholdsExamples?
Subliminal StimulationStimuli below one’s absolute
threshold of conscious awareness.
Are subliminal stimuli effective? Yes & No
Slide studies showed some emotional reactivity (called priming a response). The effects are subtle and fleeting.
Subliminal Messages: The Early Years
James Vicary claimed to have flashed the words “eat popcorn” and “Drink Coca-Cola” on a movie screen for 1/200th of a second, every 5 seconds during the movie Picnic.
He claimed popcorn sales increased 58% and Coke sales increased 18%.
Vicary’s experiment was never successfully replicated
He later acknowledged the study was a fraud.
Recent Years: Product placement
Product placement is a form of supraliminal persuasion
• Subtle, perhaps, but not subliminal