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.