The Nature of Sensation
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Transcript of The Nature of Sensation
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The Nature of Sensation• Question to consider: How is
light or sound converted into a message to the brain?
• The Basic Process• Sensory Thresholds• Subliminal Perception• Extrasensory Perception
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The Nature of Sensation• Sensations
– Raw senses, the actual experience– What are your 5 senses?
• Perceptions– Giving meaning to raw data
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The Basic Process• Receptor cell
– Specialized cell that responds to energy
• Now for the sensory process…
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The Basic Process• Energy (light waves,
sound vibrations, airborne chemicals, etc.) stimulate a receptor cell
• If the energy is strong enough, the message goes to your brain
• Each sensory organ “invades” the brain on a different channel
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The Basic Process• Hard part…• Signals carried by optic nerve NOT
“visual” - we cannot see them• Signals carried by the auditory nerve
are NOT “audible” - we cannot readily hear them
• These signals produce an experience we interpret, or perceive, as visual or audible in the brain
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The Basic Process• Johannes Müller
discovered this one-to-one relationship– Stimulating a
specific nerve produces a specific perceptual experience
– He called this the doctrine of specific nerve energies
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Stop, Drop, Test it Out!• Close your eyes. No, I’m not joking!• Now gently press on your eyelids• What did see?!• Perhaps a flash of light?!
• This tells us that the optic nerve carries signals to the brain caused by more than just light waves– The brain interprets pressure as
visual
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The Basic Process• Quick test: How would your brain
interpret a stream of water trickling into your ear?– AS SOUND!!!– The auditory nerve would be stimulated
and your brain would hear
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Sensory Thresholds• Absolute threshold
– Minimum amount of energy required to produce a sensation
– Point at with people can detect a stimuli 50% of the time
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Sensory Thresholds• The threshold for each sense is LOW!
– Taste: 1 gram salt in 500 liters of water– Smell: 1 drop perfume in 3-room apt.– Touch: Wing of beam falling on cheek
from height of 1 cm– Hearing: Tick of a watch 20 ft away
(only when quiet)– Vision: Candle flame from 30 miles
away on a clear night
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Sensory Thresholds• Sensory adaptation
– When your sensory threshold changes– Your senses adjust to the amount of
stimulation
• Example: When you walk in a dark room, can you immediately see?– No– But, as you remain in the room your
eyes adjust
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Sensory Thresholds• Difference threshold
– Also called the JND– Smallest change in energy that can be
detected 50% of the time
• Example: You are holding 1 lb, 15 lbs are added, will you notice?
• However… You are holding 15 lbs, 1 lb of weight is added, will you notice?
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Sensory Thresholds• The difference
threshold is proportional– A 2% change of
weight is necessary to notice a change
– This is called Weber’s law
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Subliminal Perception• Can we respond to stimuli that are
below the absolute threshold?
WHAT????
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Subliminal Perception• People CAN be influenced by
information they are not consciously aware of– Seen in laboratory studies– Does NOT mean people are
brainwashed by advertisements, music, or self-help tapes
– Outside of labs, subliminal messages seem to be ineffective marketing tools
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Subliminal Perception• Links to try!
– http://www.youtube.com/watch?v=U16J22QsFT8
– http://www.youtube.com/watch?v=PVrOFt-0-e0&feature=related
– http://www.youtube.com/watch?v=Ng6hQfGzQig&feature=related
– http://www.youtube.com/watch?v=2NPKxhfFQMs
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Extrasensory Perception• You probably know this as ESP
– A response to an unknown event not presented to any known sense
• Parasychology– Field of psychology that analyzes ESP
and psychic phenomenon• Not yet proven to exist
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Extrasensory Perception• Clairvoyance
– Aware of an unknown object or event– Example: You just know the missing card
must be under the area rug• Telepathy
– Knowledge of another person’s thought or feelings
• Precognition– Foreknowledge of future events– Example: You are positive that NH
football team will win the homecoming game 14 to 6