Sensation

SensationThe process by which our five senses and nervous system receive stimulus from the environment.

PerceptionThe process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Bottom-Up ProcessingAnalysis that begins with the sense

receptors and works up to the brain’s integration of sensory information. You begin by examining small details and piece them together into a larger picture.

Top-Down ProcessingInformation processing guided by

higher-level mental processesAs when we construct perceptions

drawing on our experience and expectations

Processing Sensation

Read the sentence below

i _m eati _ g ch_co_la_te

Top-Down Previous knowledge and memory mentally

“fills the gaps” allowing us to read the sentence

Bottom-Up Look at the feature of the word (lines,

slants, etc.), then look at the letters of each word, and finally the word in its entirety

We only use light energy to see.

WavelengthThe distance from the peak of one light wave to the peak of the next.

The wavelength distance determines the color of the light we perceive.

Intensity (Brightness)The amount of energy in a light wave is... determined by the height of the waveThe higher the wave...

the more intense the LIGHT is.

The Detroit Red wings logo is anything but red.

The jersey actually rejects the long wavelengths of light that to us are red. The red is reflected off and we see it.

Light has no real color.

It is our mind that perceives the color.

Perception of Color

Negative Afterimage•If you stare at

one color and then look at white space, you see a color afterimage in the complementary hue of the original stimulus

Structure of the Eye

Pupil - adjustable opening in the center of the eye Iris - a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil openingLens - transparent structure behind pupil that changes shape to focus images on the retina

Structure of the Eye

Cornea - Transparent outer covering of the eye.Retina - Contains visual sensory receptors.Fovea - Point of central focus. Optic Nerve - Pathway to the brain’s visual cortex.

•Rod and Cones: The two types of photoreceptors in the eye.

•Rod and Cones: The two types of photoreceptors in the eye.

• Rods are more numerous (120 million) and work well in dim light.

•Rod and Cones: The two types of photoreceptors in the eye.

• Rods are more numerous (120 million) and work well in dim light.

• Cones see color (6-7 million – macula) and don’t work well in dim light.

•That is why you don’t really see colors at night.

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Blind Spot occurs is the location in the retina where the visual cortex exits to the brain, there are no receptors thereYou don't notice this blind spot in

every-day life, because your two eyes work together to cover it up. Our brain, typically, fills in that missing piece based on what it estimates to be there

Blindsight—we can see things we don’t perceive

Blindspot & Blindsight

To find the blindspot, draw a filled-in, 1/4"-sized square and a circle three or four inches apart on a piece of white paper.

Blindspot experiment

Hold the paper at arm's length and close your left eye. Focus on the square with your right eye, and slowly move the paper toward you. When the circle reaches your blind spot, it will disappear! Try again to find the blind spot for your other eye. Close your right eye and focus on the circle with your left eye. Move the paper until the square disappears.

What happened when the circle disappeared? Did you see nothing where the circle had been? No, when the circle disappeared, you saw a plain white background that matched the rest of the sheet of paper.

This is because your brain "filled in" for the blind spot - your eye didn't send any information about that part of the paper, so the brain just made the "hole" match the rest. Try the experiment again on a piece of colored paper. When the circle disappears, the brain will fill in whatever color matches the rest of the paper.

Octopuses Don’t have blind spots.

…so look out.

•Everything you see is actually upside down.

• Your visual processing center in your brain then processes this message quickly.

Copyright © 2010 Ryan P. Murphy

NEARsighted FARsightedFaraway objects are seen more clearly than near objects b/c eye is shortened.

Nearby objects are seen more clearly than distant objects b/c eye is elongated.

•Which is nearsightedness, and which is far sightedness?

A B

Farsightedness

A

Farsightedness Nearsightedness

•Is this person nearsighted or far sighted?

Copyright © 2010 Ryan P. Murphy

•Answer! Farsighted

Copyright © 2010 Ryan P. Murphy

Absolute Threshold

For all senses, it is the minimum amount of stimulation that an organism can detect.

We have a very sensitive absolute threshold for vision:only 3 photons on single receptor across a moment of time will trigger a detection

Sharks can detect a single drop of blood in thousands of gallons of water whereas we can taste a teaspoon of sugar in only 2 gallons.

Weber’s LawTo perceive a difference between 2 stimuli, they must differ by a constant percentage; not a constant amount.Example: If 105g can be distinguished from 100g, the noticeable difference is 5g.

If the mass is doubled, the amount needed to perceive a change in stimuli also doubles to 10g, so that 210g can be distinguished from 200g.

Weber’s Law ExperimentTry the following experiment:

•Hold one pen/pencil in one hand and two pens/pencils in your other hand. Can you tell the difference in weight?

•Now put those into each of each of your shoes. Now can you tell the difference?

Weber’s Law In PracticeIf you make $5 an hour a 25 cent hour raise will be noticeable.But at $10 an hour you may need 50 cents to really realize a difference.

In car sales, after the $20,000 price tag, customers won’t really notice the $500 stereo.

What if we could sense everything?

Life would hurt.So we can only take in a window of what is out there.

Sensory AdaptationDiminished sensitivity as a result of constant stimulation.We don't really detect physical energy

Our senses are more evolved to detect changes in physical energy

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

Selective AttentionThe focusing of conscious awareness on a particular stimulus.

•Typically, we filter out what we deem to be unnecessary or unimportant without being aware of the fact that we are exercising this filtering process.

•As a result, what we think is not always correct. It is simply a result of our beliefs, prior experiences, and the arousal of our senses that play a role in our editing function.

Another example of selective attention is: Cocktail Party

EffectThe ability to listen to

one voice among many.

Stroop test #1

•Read the color of the word

• Piece of cake right??

Stroop test #2

•Read the word and time yourself – NOT the color

• Still easy right?

Stroop test #3•Now….. Read the color of the word and time

yourself – NOT the word

• Not so easy, EH?

•Read the word in each box

threethree

oneoneoneone

fourtwotwotwo

fourfour

twotwotwo

three

twotwotwo

three fourfour

oneoneone

threethree

twotwotwotwo

four

oneone two three

three

oneoneoneone

fourfour

twotwotwo

oneoneone

•Now say the number of words in the box

threethree

oneoneoneone

fourtwotwotwo

fourfour

twotwotwo

three

twotwotwo

three fourfour

oneoneone

threethree

twotwotwotwo

four

oneone two three

three

oneoneoneone

fourfour

twotwotwo

oneoneone

Directional Stroop

•Name the word in the box

•Give the Direction of the word in the box• Is it on the top? On the left? Etc…..

Stroop EffectJ. Ridley Stroop discovered this phenomenon in the 1930’s.

He also found that it doesn’t improve with practice!

Two Explanations have been been given:

1. Speed of Processing Theory: the interference occurs because words are read faster than colors are named.

2. Selective Attention Theory: the interference occurs because naming colors requires more attention than reading words.

We do not perceive the world how it really is, but as it is useful for us to perceive it.