Perception

January 9, 2018 | Author: Anonymous | Category: Social Science, Psychology, Conformity
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We do not perceive the world how it really is, but as it is useful for us to perceive it.

Perception The process of organizing and interpreting information we get from our senses •enables us to recognize meaningful

objects and events.

In transforming sensations into perceptions, we create the meaning

Perception • The way we interpret the world in many ways dictates our sense of reality

• Even if our senses are amazing, if our perception is skewed we will not understand the information we sense

Selective Attention • Any moment we focus our awareness on only a limited aspect of all that we experience • Example– directions video

Cocktail Party Effect • Ability to attend selectively to only one voice among many

Visual Capture The dominance of vision over other sense modalities, such that what is felt or heard conforms to what is seen.

Perceptual Illusions • Once we have attended to certain stimuli, how do we organize them into meaningful perceptions?

• Dalmatian Picture

Turn to page 234

Perceptual Illusions

Size-Distance Relationship Both girls in the room are of similar height. However, we perceive them to be of different heights as they stand in the two corners of the room.

Both photos from S. Schwartzenberg/ The Exploratorium

Ames Room

The Ames room is designed to demonstrate the sizedistance illusion.

Lightness Constancy

The color and brightness of square A and B are the same.

Thanks Noodle

Perceptual Illusions

Perceptual Illusions

Perceptual Illusions

Perceptual Illusions

Visual Capture • When vision competes with other senses, vision usually wins- known as visual capture • For example- watching a movie, in theatres we believe the sound is coming from the screen where people are talking, when really, it’s not

Perceptual Organization • To transform sensory information into meaningful perceptions, we must organize it: we must perceive objects as distinct from their surroundings, see them as having a meaningful and constant form, and discern their distance and motion.

Perceptual Organization When vision competes with our others senses, our vision usually wins – a phenomenon called visual capture. How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that the brain creates a coherent perceptual experience that is more than simply a sum of the available sensory information, and it does this in predictable ways. Gestalt psychology examines a person’s total experience because the way we experience the world is more than just an accumulation of various perceptual experiences.

Gestalt • German scientist became intrigued with how the mind organizes sensations into perceptions • Given a cluster of sensations, the human perceiver organizes them into a gestalt • Described principles by which we organize our senses into perceptions

Gestalt Psychology

• Gestalt means “an organized whole” • These psychologists were concerned with how and why we GROUP objects together. • They stated that humans can not help but perceive stimuli in groups rather than individual or isolated elements This explains why we see a cube and not a set of isolated holes or circles

Perceptual Organization: Gestalt  Grouping  the perceptual tendency to organize stimuli into coherent groups

 Grouping Principles     

proximity--group nearby figures together similarity--group figures that are similar continuity--perceive continuous patterns closure--fill in gaps connectedness--spots, lines, and areas are seen as unit when connected

Remember? • Our yen for assembling visual features into complete forms involves bottom-up processing, starting with entry-level sensory analysis, as well as top-down processing that uses our experiences and expectations to interpret those sensations • Remember- our brains do more than just register information about the world. We constantly take in information and infer perceptions that make sense to us #

Which one is better looking?

Perceptual Organization  Figure and Ground--organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Perceptual Organization: Grouping Principles

Proximity • We group nearby figures together.

Proximity • Grouping nearby figures together

3 sets of parallel lines not six separate lines

Similarity • Figures similar to each other we group together.

Similarity • Grouping together figures that are similar to each other

9 separate shapes Or Two columns and one Column?

Continuity • We perceive smooth, continuous patterns rather than discontinuous ones

Continuity • Perceiving smooth continuous patterns not discontinuous ones

Connectedness • When they are uniform and linked, we perceive spots, lines, or areas as a single unit

Perceptual Organization: Closure

 We fill in gaps to create a complete, whole object

Closure • Filling in gaps to create a complete, whole object

Perception Our perceptions are affected by the biology of our sensory systems, but also by our previous experiences and cultural expectations.

Or in other words our…

Schemas

Perception is also often based on… 

Perceptual Set 

A bias to perceive one thing and not another when looking at things in our world Sort of the same thing as a mental set  So in some ways it can cause us to make errors in judgments when we are trying to perceive the world through our senses 

What do you see? • What you see in the center is influenced by your perceptual set

Perceptual Set

Bill Clinton and who?

Perceptual Set-Schemas

Which is the real Madonna?

Perceptual Set-Schemas

• When we hold the eyes as a constant it is difficult to identify the correct Madonna. Now that the image is rotated it is easy to tell the difference.

Perceptual Illusions 



Used to reveal how we normally organize and interpret sensations

Optical or Visual Illusions 

Discrepancies between the appearance of a visual stimulus and its physical reality

Form Perception • Figure-Ground

Relationship • When we look at objects we see the object as the figure and its surroundings as the background – Airplane in the sky

Depth Perception  The

ability to see objects in three dimensions although the images that strike the retina are two dimensional.  Allows us to judge distance.

Perceptual Organization Depth Perception

Visual Cliff

Used to test infants depth perception

Perceptual Organization: Depth Perception  Depth Perception  ability to see objects in three dimensions  allows us to judge distance

 Binocular cues  retinal disparity  images from the two eyes differ  closer the object, the larger the disparity

 convergence  neuromuscular cue  two eyes move inward for near objects

Perceptual Organization: Depth Perception  Monocular Cues  relative size  smaller image is more distant

 interposition  closer object blocks distant object

 relative clarity  hazy object seen as more distant

 texture

coarse --> close fine --> distant

Perceptual Organization: Depth Perception  Monocular Cues (cont.)  relative height  higher objects seen as more distant

 relative motion  closer objects seem to move faster

 linear perspective  parallel lines converge with distance

 relative brightness  closer objects appear brighter

How do we transform twodimensional objects to threedimensional perception?  Binocular 

Cues:

depth cues that depend on two eyes

•Monocular Cues: •depth cues that depend on one eye

Binocular Cues



Convergence 

eyes turn in as objects get close

Pen together two eyes- try with one

Binocular Cues Retinal disparity (or binocular disparity): Images from the two eyes differ. Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset.

Monocular Cues Tricks that we use to judge depth perception

What makes them monocular is that you need only one eye to use them. So if you lose one eye in a tragic ping-pong accident…don’t worry…just wear an eye patch

Monocular Cues Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

Monocular Cues

Interposition: Objects that occlude (block) other objects tend to be perceived as closer.

Rene Magritte, The Blank Signature, oil on canvas, National Gallery of Art, Washington. Collection of Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli.

Interposition

if something is blocking our view, we perceive it as closer

Monocular Cues Relative Height: We perceive objects that are higher in our field of vision to be farther away than those that are lower.

Image courtesy of Shaun P. Vecera, Ph. D., adapted from stimuli that appered in Vecrera et al., 2002

•Relative Size

if we know that two objects are similar in size, the one that looks smaller is farther away

Relative Size

Monocular Cues Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

Motion Perception What tools do we use to perceive motion…  Stroboscopic movement  Perceiving continuous movement  Example • Movies Flip Book Example

Monocular Cues Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance.

Linear Perspective at Work

Monocular Cues Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Shading can imply where a light source is and thus imply depth and position. The ones that are shaded on the left seem to be sticking out towards us. From “Perceiving Shape From Shading” by Vilayaur S. Ramachandran. © 1988 by Scientific American, Inc. All rights reserved.

Linear Perspective Parallel lines seem to converge with distance.

Phi Phenomenon • An illusion of movement created when two or more adjacent lights blink on and off in succession.

Perceptual Constancy 

Perceptual Constancy 

  

Perceiving objects as unchanging even as light and retinal images change Shape and size Lightness Color (indoor vs. outdoor)

Re-Cap of Perspective: Perceptual Constancy 

Perceptual Constancy- Tendency for perceptions of objects to remain relatively unchanged in spite of changes in raw sensations 







Brightness Constancy: piece of white paper does not change when it moves from am dimly lit room to a brightly lit room Color constancy: colors do not seem to change much in spite of different conditions of light Size constancy: dollar bill from 1 foot and 10 feet with seem different in size, however we do not perceive it as different because familiar objects do not change in perceived size as different distances Shape constancy- a penny seen straight on is circular, from an angle it’s oval however we continue to perceive it as circular

Re-Cap: Depth Perception  

    

Texture Gradient- texture of objects more severe up close Linear Perspective- images cast smaller images on retina when they are more distant, parallel lines appear to grow closer further away Superposition- Closer objects tend to be partially in front of distant objects Shadowing- shadow suggest depth of object Speed of movement- objects further away move across the field vision slower Aerial Perspective- distant objects look hazy Accommodation- shape of lens of eye changes to focus on visual images

What does this say?

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

Call me….

703-855-78S2

Top-Down vs. Bottom Up

Top-Down Processing Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a word are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can still raed it wouthit a porbelm. This is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the word as a wlohe.

Philosophers have debated the origin of our perceptual abilities: Is it nature or nurture? What do you think?

Beliefs • German philosopher Immanuel Kantknowledge comes from our inborn ways of organizing sensory experience • British philosopher John Locke- through our experiences we also learn to perceive the world

Could a person who is blind from birth distinguish this visually if they gained sight as an adult?

Critical Period • Critical period of vision is at birth through infancy of humans, cats, monkeys

Cataracts • Human infants born with opaque lens (cataract) will typically have corrective surgery within a few months • Brain network for corrected eye develops quickly, enabling vision to occur normally

Perceptual Adaption • With vision, the ability to adjust to an artificially displaced or even inverted visual field – Example: wearing a new pair of glasses (may be fuzzy at first, a few hours or days, eyes will adjust)

Human Factors Psychologists • A branch of psychology that helps to determine how appliances, machines, etc. should be created in order for people to use them naturally

Is it really possible?

Extrasensory Perception • ESP (extrasensory perception) – The controversial claim that perception can occur apart from sensory input

• Parapsychology – The study of paranormal events such as – Telepathy – mind-to-mind communication – Clairvoyance – perception of remote events

ESP Three types of ESP: 1. Telepathy- mind to mind communication 2. Clairvoyance- perceiving events as they are taking place 3. Precognition- perceiving future events Also associated with ESP, psychokinesis (“mind over matter”

Claims of paranormal phenomena include astrological predictions, psychic healing, communication with the dead, and out-of-body experiences

• http://viscog.beckman.illinois.edu/djs_lab/d emos.html • www.grand-illusions.com • http://www.mindhacks.com/ • http://psych.hanover.edu/Krantz/tutor.html • http://users.skynet.be/J.Beever/pave.htm

• http://philomel.com/musical_illusions/ • http://www.audiodesignline.com/20430042 9

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