SensationVision

The EyeTheories

Hearing

The Ear TheoriesOther Senses

SmellTaste

Pain

Gestalt Principles

Perceptual Constancies

Perception

Basic Principles

Visual Illusions

Depth Perception

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Sensation and Perception

Sensation

• The process by which our sensory receptors and nervous system receive stimuli from the environment.

Energy v. Chemical senses

Energy Senses Chemical Senses

Perception

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

Sensation vs. Perception

Bottom-up Processing

Analysis of the stimulus begins with the sense receptors and works up to the level

of the brain and mind.

Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

Top-Down Processing

Information processing guided by higher-level mental processes as we

construct perceptions, drawing on our experience and expectations.

THE CHT

Example of Top-Down Processing:

Aoccdrnig to rscheearch at Cmabridge Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tigng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

What if we could sense everything?

Life would hurt.

So we can only take in a sliver of what is out there.

This is the study of psychophysics: relationship between physical stimuli and our psychological experiences to them.

Absolute Threshold• The minimum stimulation needed to

detect a stimulus 50% of the time.• Ex: how far away do you need to

stand to hear a watch ticking? (avg. = 20 ft)

• Ex: how far away can you stand and see a candle flame in the dark at night? (avg. = 30 miles)

No

Detection

Intensity

AbsoluteThreshold

Detected

YesYesNo No

Observer’s Response

Tell when you (the observer) detect the light.

Absolute Thresholds: (the other 3 senses)

• Taste: 1 gram (.0356 ounce) of table salt in 500 liters (529 quarts) of water

• Smell: 1 drop of perfume diffused throughout a three-room apartment

• Touch: the wing of a bee falling on your cheek from a height of 1cm (.39 inch)

Signal Detection Theory

• Assumes that we do NOT have an absolute threshold.

• We detect stuff based on our experiences, motivations, expectation and fatigue level.

Subliminal Threshold

Subliminal Threshold: When energy of the

stimulus is below one’s absolute threshold for conscious awareness.

Kurt S

cholz/ Superstock

Subliminal Perception Sensation without perception?

Quick Survey1. Do you think you are influenced by everyday

advertisements that you perceive consciously (e.g. movies, beverages)?

2. Do you think you are influenced by subliminal messages in advertising?

Suppose you had a choice to listen to one of two speeches that argued against a position you believe in, such as whether marijuana should be legalized. In speech A, the person presents arguments against your position; in speech B, all arguments are presented subliminally.

Which speech would you rather listen to?

1. 69% chose speech A; 31% chose B (subliminal)• Why are people afraid? Should you be?

• 80% college students preferred not to receive a subliminal message b/c they thought it might

influence them in an undesirable way.

…You Decide Could 1/30th of a second really influence impressions of

Al Gore?

We are not obedient to Subliminal Messages

• Research shows that the effect only occurs in controlled laboratory studies

• Research outside the laboratory shows no significant effect of subliminal information

• We don’t blindly obey!• Placebo Effect with subliminal self help tapes

Subliminal Messages in Logos

Amazon has everything – from A to Z!

The Big 10 Conference really has 11 teams, but didn’t want to change their name.

Fed Ex will ship your items fast! Check out the speedy arrow!

EAT POPCORN

Vicary’s Study

• New Jersey, 1957: – Over 6 weeks, 45,699 people see subliminal

ads– “Eat Popcorn” – sales up 57.5%– “Drink Coke” – sales up18.1%

• “Minds have been broken and entered”

Except . . . .

• The Vicary “Eat Popcorn/Drink Coke” Study well. . . .

• In a 1962 interview, Vicary admitted that he had made the whole thing up!

Backmasking

• A recording studio technique where backward messages are deliberately superimposed on the soundtrack

Not the last of it…

• Sexual imagery in ads?

Difference Threshold• The minimum difference that a person

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

Difference (jnd)

Can you tell the difference?

Difference Threshold

Difference Threshold: Minimum difference between two stimuli

required for detection 50% of the time, also called just noticeable difference

(JND). DifferenceThreshold

Tell when you (observer) detect a difference in the light.

No

Observer’s Response

No Yes

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

between two stimuli, they must differ by a constant percentage; not a constant amount.

Applying Weber’s Law• If the cost of a soda goes up by $0.25, it is

very noticeable. If the cost of a television goes up by $0.25, it is not noticeable.

vs.

• In sales – sell the more expensive item first. Then accessories or add-ons don’t seem so bad (ie, buying satellite radio for your car. After agreeing to spend $20,000, an extra $500 a year doesn’t seem ridiculous).

Weber’s Law

Weber fraction: k = dI/I.

Stimulus Constant (k)

Light 8%

Weight 2%

Tone 3%