Sensation. Prosopagnosia anyone? 7Wn-Y 7Wn-Y

Sensation

Prosopagnosia anyone?

• http://www.youtube.com/watch?v=dxqsBk7Wn-Y

• http://www.youtube.com/watch?v=q8cXus7SNQY

Sensation

• The process by which our sensory receptors and nervous system receive stimulus from the environment. (stuff inputed from our 5 senses). A person with prosopagnosia has normal sensation

Perception

• The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. The same person with prosopagnosia has almost normal perception. She can recognize some aspects of the person but cannot put the whole picture together

• Bottom Up v. Top Down Processing

• Bottom up – a progression from individual elements to the whole (start small then work your way up) (start focusing on trees, then you pay attention to the forest).

• Top-down processing – start with the forest and work your attention down to the individual tree.

Bottom Up Look at the lines to sort out the picture

Top down• At first you see the big picture, then you

notice the parts (the faces)

Top-down processing

Top down processing

The word face makes you see the face first. It alters your perception.

Selective Attention• The focusing of conscious awareness

on a particular stimulus. Demonstration anyone?

Shhhh!!!!

• http://www.youtube.com/watch?v=vJG698U2Mvo

An example of selective attention is:

Cocktail Party Effect: ability to listen to one voice among many.

Selective Attention

• 5 senses take in about 11,000,000 bits of info a second. Consciously process about 40

• Possible problem with ADD people- cannot block out stimuli

Inattentional Blindness or Selective Inattention- failing to see visible objects when our

attention is directed elsewhere (gorilla)

• http://www.youtube.com/watch?v=Qb-gT6vDrmU

Change Blindness- failing to notice changes in the environment

• http://www.youtube.com/watch?v=lEpekmn0QOs

• • https://www.youtube.com/watch?v=1nL5ulsW

• https://www.youtube.com/watch?v=ubNF9QNEQLA

Choice Blindness

• http://www.youtube.com/watch?v=wRqyw-EwgTk

Thresholds

• Right now we are being hit with x-rays, radio waves, infrared light, sound waves = Energy

• Most of which we are not aware – animals use another sense- bats for example use echo location

• Our senses are only open a crack allowing us a restricted awareness of this energy

• Psychophysics looks at the energy we can detect and its effect on our psychological experiences

Absolute Threshold-The minimum amount of stimulation necessary to detect a touch,

smell, sound, light,- The smallest amount needed to detect a stimulus. Changes

• The minimum stimulation needed to detect a stimulus 50% of the time.

Subliminal Messages

• Below your absolute threshold of conscious awareness

• Subliminal messages prime people for a later response

• Mostly a placebo- believe they work and they do• http://www.youtube.com/watch?v=2Kur8p4yCao

&safety_mode=true&persist_safety_mode=1&safe=active

Signal Detection Theory

• When we are able to detect the presence of slight stimuli among background interference – noise

• People respond differently to the same stimuli

• Depends on a person’s experience, motivation and alertness

Difference Threshold• The minimum difference that a person can

detect between two stimuli.• Also known as Just Noticeable Difference

Can you tell the difference?

Girls are better at this.

Weber’s Law• The idea that, to perceive a difference

between two stimuli, they must differ by a constant percentage; not a constant amount. Must differ in weight by 2% ex- 50 oz wt must differ by 1 ounce, 100 oz by 2 oz

Application for Weber’s Law

• Would you drive 10 minutes away to save $20 on a meal?

• Would you drive across town to save $100 on a $30,000 car?

• Since $100 is such a small percentage of a car’s price, you don’t think of it as much money.

Sensory Adaptation

• Diminished sensitivity as a result of constant stimulation.

Can you feel your underwear?

TransductionConversion of one form of

energy to another.How is this important when studying sensation?

Stimulus energies to neural impulses.

For example:

Light energy to vision.

Chemical energy to smell and taste.

Sound waves to sound.

Vision

We only use light energy to see.

Two physical characteristics of light help determine our sersory experince of them?

Wavelength• The distance from the peak of one light wave to

the peak of the next.

•The distance determines the hue (color) of the light we perceive.

Intensity

The amount of energy (brightness) in a light wave.

Determined by the height or amplitude of the wave.

The higher the wave the more intense the light is.

Rods = b/w (light)Cones = color

Parts of the Eye

• Light passes through the cornea which protects the eye and pupil

• Pupil surrounded by the Iris- a colored muscle that controls light

• Behind the pupil is the lens that focuses incoming light rays onto the retina

• The lens focuses its rays by changing its curvature- accommodation

• Fovea Area of sharpest vision – back of eye• The retina houses the cones and rods (these are the

neurons that change light into neural impulses)

Parts of eye continued

• Cones = color and clear vision work best in bright light rods- black and white, useful in dim light- neurons in the retina that are light sensitive

• Optic nerve carries information to the brain via the thalamus

• Brain that turns the image ride side up• Where the optic nerve leaves the eye there are no

receptor cells creates a blind spot – no rods or cones (do demo)

• Cones cluster near the fovea which is the retina’s area of central focus

Receptors in the Human Ewye: Rod Shaped Roda and

Feature detection

• Feature detection cells get their name from their ability to respond to a scene’s specific features: edges, lines angles, movements ex: recognize faces in the right temporal lobe just behind the right ear. Damage to this ear may render you incapable of recognizing faces

Figure 4.14 The telltale brain Looking at faces, houses, and chairs activates different brain areas in this right-facing brain.

Parallel Processing• The processing of several aspects of a

problem simultaneously.

Color Motion Form Depth

How do we see in color?

What color is this dragon?

• The dragon is anything but red.

• The dragon rejects the long wavelengths of light that to us are red- so red is reflected of and we see it.

• Also, light has no real color.

• It is our mind that perceives the color.

Afterimages

• On the next few slides are afterimages.

• Stare at the center for about 20 seconds.

• Then I’ll explain why they happen.

• The phenomenon of a negative afterimage is caused by opponent processes. After staring at one object for a long time, the stimulated cells use up resources, and begin to get 'tired'. Once the object is removed, these cells will have to fire below baseline for a bit to recover lost resources. Meanwhile, their opponent cells will fire at baseline- at a relatively higher rate. This causes a negative afterimage. Try it out!

Stare at the red dot

Two major color theories

Young-Helmholtz Trichromatic (three color) Theory

• Realized that any color can be created by combining the light waves of three primary color-

•So they guessed that we have 3 different types of receptor cells in our eyes. Together they can pick any combination of our 7 million color variations.

•Most colorblind people simply lack cone receptor cells for one or more of these primary colors.

An Explanation

• The red cones react most strongly to red light, but will also react to colors close to red in the spectrum, so the yellow light will stimulate them a little. Similarly, yellow light will stimulate the green cones a little. So pure yellow light will produce a tell-tale signal of some red and some green. Our brain interprets this as yellow.

The brain can also be fooled by looking at a mixture of red and green light. While red and green lights do not actually mix physically, the mixture will stimulate the eye in the same way as yellow light, so our brain interprets it as yellow as well.

• If you can’t see the number then you are missing one of your cones.

Are you Color Blind?

• http://www.youtube.com/watch?v=Mrz8Jsfoy-c

• Basically, opponent processing color theory states that nueronal activity is antagonistic in 3 different groups of cells. In other words, stimulation of one cell causes its partner to fire below baseline, and vice versa. There are 3 oppositional pairs.-red/green-blue/yellow-black/white

So for an example, if we stare at a red stop sign, all of our 'red' cells will fire rapidly, while all of our green cells will fire below baseline.

Stare at one figure for 30 seconds and then look at the white box and blink. RepeatFor the other figure.

Hearing

Aka: Audition

Hearing test

• http://www.youtube.com/watch?v=VxcbppCX6Rk&feature=youtu.be

Frequency the number of complete wavelengths that pass through point at a given time. This

determines the pitch of a sound.

Amplitude is how loud the sound is. The higher the crest of the wave is the louder the sound is. It

is measured in decibels.

Figure 4-5Figure 4-5

The Human EarThe Human Ear

•http://www.youtube.com/watch?v=0jyxhozq89g&list=PL2920A92123EAF834&index=17

Transduction in the ear• Sound waves hit the eardrum

then hammer then anvil then stirrup then oval window.

• Everything is just vibrating.• Then the cochlea vibrates.• The cochlea is lined with

mucus called basilar membrane.

• In basilar membrane there are hair cells.

• When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti.

• Sent then to thalamus up auditory nerve.

It is all about the vibrations!!!

How do we perceive differences in pitch?

There are two theories……..

Helmholtz’s Place Theory• We hear different pitches

because different sound waves trigger activity at different places along the cochlea’s basilar membrane.

• High frequencies = large vibrations near the beginning of the cochlea’s membrane

• Low frequency near the end

Frequency Theory

• All the hairs vibrate but at different speeds.

Frequency Theory

• We sense pitch by the basilar membrane vibrating at the same rate as the sound.

• But this theory has trouble explaining high pitch sounds because our hairs cannot vibrate at certain speeds.

• This problem can be explained using the volley principle.

Why do we have two ears? Allows us to hear stereophonic or 3

dimensional hearing

Hearing loss

• Conduction Hearing Loss: caused by damage to mechanical system of ear. Punctured eardrum, or tiny bones in the middle ear lose the ability to vibrate

– Sensorineural hearing loss (nerve deafness): caused by damage to cochlea’s receptor cells or to auditory nerves. More common, Causes: loud noise, biological changes: aging, heredity. Solution: Cochlear implant- highly controversial

• Use skin the largest organ in the human body

• Hairy skin detect movement and pressure

• Glaborous skin- no hair cells more sensitive: lips, palms, bottoms of feet

• Pressure has identifiable receptors

• 4 basic skin sensations: pressure, warmth, cold and pain

Kinesthetic Sense

• Tells us where our body parts are.

• Sense of the position and movement of your body

• Proprioception- loss of all feeling below the neck cannot move (video)

Without the kinesthetic sense you could not touch the button to make copies of your buttocks.

•http://www.youtube.com/watch?v=FKxyJfE831Q&list=PL2920A92123EAF834&index=97

Vestibular Sense

• Tells us where our body is oriented in space.

• Our sense of balance.

• Located in our semicircular canals in our ears.

What is vestibular sense?

• Vestibular sense: monitors your head and your body’s movements. This equilibrium is in your inner ear

• Fluid in the inner ear which is found in the vestibular sacs and semicircular canals moves when you rotate your head

• This movement activates hair cells that send messages to your cerebellum which allows you to sense your body position and maintain balance.

• Spinning round and stopping quickly fools your brain that you are still spinning and you get dizzy. It is an illusion

• Once your fluid and kinesthetic receptors return to neutral you no longer feel dizzy

• Let’s try it

Pain- your body’s way of telling you something is wrong

• Biological Influences-No central location for pain receptors. Many ways to trigger pain.

• Noceptors-sensory receptors that detect harmful temps, pressure and chemicals

• Gate-control theory- idea that your spinal cord has a neurological gate that blocks pain signals or allows them to pass to the brain

• Endorphins help

Pain Control

• Placebos- when given fake pain killing placebos the brain was tricked into releasing real ones “Believing becomes reality

• Distracting with pleasant images• Exercise• Massage• Pain is in the brain, diverting the brain’s attention

may bring relief

Smell and Taste

Was I born to love peanut butter & jelly?

What is the bigger question here?

Nature versus Nurture

Figure 4-6Figure 4-6

The Olfactory SystemThe Olfactory System

Why do we study smell and taste together?

• SENSORY INTERACTION: the principle that one sense may influence another.

Sensory Interaction

• SI happens with other senses• McGurk effect- hear someone say ba but the

mouth looks like is says ga we perceive da• Some people experience synesthesia- one

sensation produces another examples: hearing something may activate color sensitive regions and produce color

• Seeing a number can provoke a taste

Annoying MrGurk effect Video

• http://www.youtube.com/watch?v=jtsfidRq2tw

Sensation and PerceptionSynesthesia Unusual condition in which stimulus of one

type, such as sound also gives rise to another experience such as color

Colored Hearing… most common Synesthesia is different for different people May argue vigorously with each other about

color of Tuesday or taste of Beatles music

Testing Synesthesia As quickly as possible, find the 2’s

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