1SOSC1960Discovering Mind and Behavior

Lecture 5Sensation and Perception

2 Sensation perception Sensation principles Sensory integration Visual perception

3Sensation perception Sensation: stimulation of sensory organs Perception: organization and

interpretation of sensory input Is there a one-to-one correspondence

between sensation and perception?

4A painting by Gentile and Giovanni BelliniCirca 1480

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9Just count the little black balls...

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The Ebbinghaus illusion

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All these examples show that Our interpretation of the stimuli seems to be

different from the stimuli objectively and physically out there

What we sense What we perceive Our brain is constructing images based on the

sensory input

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Stimulus Physical energy that produces a response in a

sense organ

Sensation principles

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A_________ thresholds The smallest intensity of a stimulus that must

be present for it to be detected

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(2 gallons = 7.5 liters)

(16 km)(48 km)

(1.5 m)(6 m)

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D_________ thresholds Also called just noticeable difference (JND) The smallest difference in stimulation required

to sense that a change in stimulation has occurred

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Difference thresholds ___________: the size of a just noticeable

difference is a constant proportion of the size of the initial stimulus (Weber fraction)

E.g., 1:50 for weight

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Difference thresholds Silent electric or hybrid vehicles are becoming

popular, but they could threaten the safety of pedestrians who can't hear the vehicles approaching because the sound from the vehicle is too small to be heard with the background noise in the street

http://www.scientificamerican.com/article.cfm?id=are-hybrid-cars-too-quiet&sc=rss

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Sensory ___________ Reduction or disappearance of sensory

responsiveness that occurs when stimulation is unchanging or repetitious

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Our sensory receptors are most responsive to changes rather than the constants in stimulation

It frees us from responding to unimportant or unnecessary, abundant information

But sometimes it can be hazardous (consider a gas leak)

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Sensory Integration Our senses interact, working in tandem to

build our complex understanding of the world E.g. taste: vision and smell senses (video) E.g. balance: vision and skin senses (video)

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Sensory integration ______________: rare condition in which

exposure to one sensation (such as a sound) evokes an additional one (such as vision)

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http://www.youtube.com/watch?v=KApieSGlyBk&feature=related

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"When Liszt first began as Kapellmeister in Weimar (1842), it astonished the orchestra that he said: 'O please, gentlemen, a little bluer, if you please! This tone type requires it!' Or: 'That is a deep violet, please, depend on it! Not so rose!' First the orchestra believed Liszt just joked; more later they got accustomed to the fact that the great musician seemed to see colors there, where there were only tones.

Anonymous, as quoted in Friedrich Mahling, p. 230. (Translation by Sean A. Day.)

Synesthesia: seeing colors in music

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Vision by Carol Steen; Oil on Paper; 15 x 12-3/4 inches; 1996. A representation of a synesthetic vision the artist experienced during acupuncture treatment.

Synesthesia: seeing images in touch

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P_________ of our sensory system Even when one of our senses is disrupted, our

brain can rewire itself and adapt to the situation Seeing the world upside down Blind people see with their tongue

http://www.youtube.com/watch?v=OKd56D2mvN0

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Visual perception Sensation Perception

Our brain is at work, trying to make sense of the sensory input

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Are the lines straight?

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Gestalt laws of organization Gestalt psychology: to identify the principles

underlying how we organize bits and pieces of visual information into meaningful wholes

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Principle of _____________________

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Principle of _______________________

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Other principles

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What principles are being applied in this poster?

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The whole is different from the sum of its parts

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Bottom-Up and Top-Down Processing Bottom-up processing

Perception consisting of the progression of recognizing and processing information from individual components of a stimuli and moving to the perception of the whole

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Top-down processing Perception that is guided by higher-level

knowledge, experience, expectations, and motivations

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Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it dseno't mtaetr in waht oerdr the ltteres in a wrod are, the olny iproamtnt tihng is taht the frsit and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it whotuit a pboerlm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

Knowledge and Experience

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How many faces can you see?

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Expectancy Divide the class into 2 groups. Pictures will be shown to each group. At the end, I will ask you a question. Write

your answer on the lecture notes. DONT SHOUT OUT YOUR ANSWER!

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C__________ effect

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C__________ effect: What direction is the girl gazing at?

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Perceptual constancy Perceiving objects as stable and unchanging

even though the sensory patterns they produce are shifting

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___________ constancy

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______ constancy

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Depth perception The ability to view the world in three

dimensions and to perceive distance Interpretation of visual information that

indicate how near or far away objects are

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Depth perception ___________ depth cues: clues about distance

based on the differing views of the two eyes binocular disparity: objects project images to slightly

different locations on the right and left retinas, so the right and left eyes see slightly different views of the object

The closer the object, the greater the binocular disparity

Try it yourself: looking at a pen in front of you

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Depth perception _________ depth cues: clues about distance

based on the image in either eye alone (e.g., pictorial depth cues: clues about distance that can be given in a flat picture)

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56Linear perspective was used extensively during the Renaissance

The Last Supper (14951498) by Leonardo Da Vinci

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The use of relative size in Chinese painting

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60Vincent van Gogh

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Perceptual illusions In general, the perception principles help us

perceive the world accurately and efficiently But sometime these perception principles may

lead us astray Perceptual illusion: an apparently inexplicable

discrepancy between the perception of a visual stimulus and its physical reality

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Is the word black equal or different in shade than the word white?

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Are the lines equal or different in length?

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A B Outside Corner Inside Corner

M

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Ponzo illusion

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Ames room

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Ames room

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Required Reading Ch. 4