Perceptual Constancies Sensation Vision The Eye Theories Hearing The Ear Other Senses Smell Taste Pain Gestalt Principles Perceptual Constancies Perception Basic Principles Visual Illusions Depth Perception We are here

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.”

THE CHT 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)

Detection No No No Yes Yes Detected Absolute Threshold Intensity Observer’s Response Detected 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 Scholz/ Superstock

Subliminal Perception Sensation without perception? Quick Survey Do you think you are influenced by everyday advertisements that you perceive consciously (e.g. movies, beverages)? 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?

Why are people afraid? Should you be? 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.

Could 1/30th of a second really influence impressions of Al Gore? …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! Fed Ex will ship your items fast! Check out the speedy arrow! The Big 10 Conference really has 11 teams, but didn’t want to change their name.

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). Difference Threshold No No Yes Observer’s Response Tell when you (observer) detect a difference in the light.

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 fraction: k = dI/I. Weber’s Law Weber fraction: k = dI/I. Stimulus Constant (k) Light 8% Weight 2% Tone 3%