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What’s the difference between sensation and perception?
Do We have 5 senses?
• Sight
• Hearing
• Taste
• Touch
• Smell
• What about… temperature? Balance? Movement?
How does it work?
Sense receptors (specialized cells – some in the ears, some in the eyes, some on the tongue…) FIRE to stimulate sensory NEURONS which stimulate specialized paths to specialized areas of the brain (visual cortex, auditory cortex, etc) so….
Sense receptors convert physical energy (touch, heat, light) to electrical energy
How does it work?
…if we could stimulate the visual cortex of a blind person, would they be able to see?
Well… probably, yes.
Ptito (2005) – connects pattern detector to electrodes on tongue which stimulate visual areas of brain.
Synesthesia*
Something similar happens naturally to some people.
Sounds have taste or color.Colors have scents or tastes.
One synesthete who attended an orchestra concert as a child thought the lights were lowered so the audience could see the colors better!!!!!!!!!
*A fun and interesting paper topic!!
Can you believe everything you see? Do you see everything there
is to see?No, and no.
• “Visible” light – we see only certain ranges of wavelength
• Audible sound – other animals hear much different ranges of pitch
We “ build” perceptions from our sensations.
How do we perceive waves?
Vision Sound Wave…
Hue. What color is it? Shorter – blues
Longer – Reds
Pitch. What note is it? C or D or G?
Length (frequency)
Brightness – How much light does it reflect? Yellow is a ‘bright’ color
Loudness. Height (amplitude)
Saturation – just one wavelength – ‘pure’ bold; mixture – pale (white is a mixture of all wavelengths)
Timbre. Flute (pure) or electronic tone vs acoustic guitar or oboe.
Complexity (do the wavelengths vary? How much?)
From the eye to ‘seeing’
Retina: Back of the eye – location of visual sense receptors. Lens reflects images upside down onto the retina
Rods: Sensitive, but not to color; concentrated in the periphery
Cones: Sense color; concentrated in the center of the eye
Structures of the retina
chapter 6
From the eye to ‘seeing’
Once in the cortex, we construct what we’re seeing.
A few years ago, neurologists demonstrated the existence of a Halle Berry neuron.
Many years ago, Huble & Wiesel (1968) paved the way for this work: showing that particular cells they termed “feature detectors” fired for particular patterns, such as a line at a particular angle.
Gestalt principles
ProximityThings close to one another are grouped together
ClosureThe brain tends to fill in gaps to perceive complete forms
chapter 6
Gestalt principles
SimilarityThings that are alike are perceived together
ContinuitySeeing continuity in lines that could be interpreted as either continuous or abruptly shifting in direction.
chapter 6
Depth and distance perception
Binocular cues: visual cues that require the use of both eyes
ConvergenceTurning inward of the eyes, which occurs when they focus on a nearby object
Retinal disparityThe slight difference in lateral separation between two objects as seen by the right and left eyes
chapter 6
Depth and distance perception
Monocular cues: visual cues that require just one eye
Interposition: If you are blocking my view of the car, you must be closer
Linear perspective: We are fooled by this in the Muller-Lyer Illusion
Size constancy: Why does the moon appear so much larger when it’s near the horizon?
chapter 6
The Müller-Lyer illusion
chapter 6
Visual constanciesThe accurate perception of objects as stable or unchanged despite changes in the sensory patterns they produce
Shape constancy: A pie is always round even when it’s an arc on the retina
Location constancy: We see objects as still even though their image on the retina moves as we move
Size constancy: We see objects as staying the same size even though they grow smaller on the retina
Brightness constancy: We see snow as white on a cloudy day when the waves’ amplitude may send a different message
Color constancy: We see an object’s color as the same in different light, even though the reflected wavelength changes
chapter 6
How do we hear?
• Remember – sense receptors translate physical (sound waves) to electrical (neural impulse)
• Ear drum? No.• Hammer, anvil, stirrup bones? No.• All the way inside the cochlea – hair cells.
– NOTE! These are VERY fragile cells. Your MP3 player, your job, or one concert could all cause permanent hearing loss.
How do we hear?
• Gestalt principles apply to hearing, too– Proximity– Continuity– Similarity
All help us know what sounds go together, and which sounds are the ‘background noise’
Taste
How might taste help us survive?
• Sweet
• Sour
• Bitter
• Salty
• Umami(?!)
Taste
Where are the sense receptors for taste?• Inside the papillae (you can see these on
your tongue) inside the taste buds• How many taste buds do you have?
– 500 for some people– 10,000 for others– Who has more? The person who loves
jalapenos or the person who cries when they get one?
Is there a connection between smell and taste?
Many foods (chocolate, for one!) have almost no distinguishable taste without smell.
Smell is a much more sensitive sense.
• Specialized cells – sense receptors – millions of them – and there are about 1,000 different types! Each responds to a different part of a molecule’s structure.
Can you think of a category or type of smell?
• We have salty, sweet, bitter, etc for taste. What about smell?
Where does pain come from? Where does it go? Is pain a sense?• Sometimes we feel pain where there is no
damage
• Sometimes there is damage where we feel no pain
• Sometimes we feel pain where there is nothing at all
Do we feel only the pain we need to feel?
Where does pain come from? Where does it go?
• Multiple sets of neurons are involved in inhibiting or allowing pain signals to travel to the brain
• The brain sometimes sends its own messages to these neurons
What might be the benefit to the brain of “controlling” pain?
One more sense… for now
• Sometimes pain comes from within the body
• “Kinesthesis” always comes from inside the body– What messages do you need from your body
in order to walk?– Semicircular canals in the ear provide
information for “equilibrium” – our sense of balance
– Other info you need?
How do our perceptual tricks develop?
• Both inborn and learned– Feature detector cells can lose their
functionality if they are not used (Blakemore & Cooper’s 1970 study of cats)
– Infants won’t cross “visual cliff” at 6 months, and seem to notice the difference at 2 months
– If vision or hearing are restored to a blind or deaf person after infancy, perceptual skills develop only to a limited degree (“critical periods” for experience to create learning)
Are our perceptual tricks universal? More evidence of learning
• Experience: What is common in your environment• Needs/desires: Hungry? You’ll be the first to see the
picture of food• Beliefs: UFO sightings, Mother Theresa french toast• Emotions: Influence pain perception among others
(what do you see in the dark when you’re afraid?)• Expectations: Where is the typo in ths sentence?
All influence what we “see”
Can you perceive without sensing?
• What if a picture is flashed too quickly for you to ‘see’ it? Image can influence opinions/memory
• What if you are asleep and listening to a “Learn to Relax” or “Improve Your Memory” tape? Placebo effect! Whichever tape you think you’re listening to, that is the skill that will improve.
• ESP? Many, many efforts to demonstrate: well-designed studies fail. (Poorly designed studies succeed.) Remember the influence of beliefs and expectations? These probably explain most incidents of ESP.