Chapter 06 - Perception

Selective Attention

• Selective attention: focusing only on one thing at a time; focused awareness only on limited aspect of all that is capable of experiencing; you aren’t aware of nose in line of vision
• Cocktail Party Effect: (example of selective attention) ability to focus only on one voice in a huge crowd
• Unnoticed stimuli has effect: women who had listened to tunes previously played to them while unnoticed preferred it later on

Perceptual Illusions

• Visual capture: phenomenon when a conflict occurs between vision and another sense, vision dominates; vision captures other senses (overrides)
• in theaters, sound comes from behind (projector), yet perceive as from screen
• Perceiving voice coming from ventriloquist’s dummy

Perceptual Organization

• Humans organize clusters of sensation into gestalt: organized “whole”; human tendency to order pieces of info into a meaning picture
• First perceptual task: to perceive figure (object) as  distinct from  ground (background)
• Figure-ground: organization of visual field into the figure(s) that stand out from the ground
• Next, organize figure into meaningful form (color, movement, like-dark contrast)
• To process forms, use grouping: rules mind follows to organize stimuli into logical groups
• Grouped into  Proximity,  Similarity, Continuity, Closure, Connectedness (visuals on page 185, figure 6.5 and definition on page 186 of 5 edition)
• Depth perception: ability to see objects in 3D even though image sensed by retina are 2D; allows distance judgment;
• partly innate (born with)
• Gibson and Walker placed 6-14 months old infants on edge of a visual cliff (table half glass, half wood), making the appearance of a drop-off; Mothers then tries to convince infant to crawl pass the normal part of the table onto glass; most refused, indicating perception of depth
• Visual cliff: laboratory device for testing depth perception in infants/animals
• Binocular cues: depth cues that depend on both eyes
• Eyes apart, slightly different images, brain sees difference –retinal disparity: bi cue in which the greater the difference between images, the closer the object
• Convergence: bi cue in which the more the eyes turns inward, the closer the object
• Monocular cues: distance cue that are available to either eye
• Examples: relative size, interposition,  relative clarity,  texture gradient, relative height, relative motion, linear perspective, relative brightness  (definitions on pages 188-189 of 5 edition)
• Brain computes motion base partly on assumption that objects moving away is shrinking & vise versa
• Brain reads rapid series of slightly different images as movement; phenomenon called stroboscopic movement
• Another illusion of movement is phi phenomenon: perception of movement when lights blink one after the other; the lighted arrow signs on the back of parked construction trucks
• Perceptual constancy: perception that objects are not changing even under different lighting; allowing identification regardless of angle of view [a door is a door even at 45 degree (shape constancy) angle or 20 feet away(size constancy)]
• Even at same size, linear perspective causes one to see one object bigger (page 191 figure 6.13a)

Interpretation

• Formerly blind patients often can’t recognize objects familiar by touch
• Sensory restriction like allowing only diffuse, unpatterned light does no damage is occurring later in life; affect only at infancy, suggesting critical period for development
• Perceptual adaptation: ability for our vision to adjust to artificial displacement (chicks do not possess this); given goggles that shift vision 30 degrees to left, humans learn to adjust actions 30 degrees to left
• Roger Sperry surgically turned eyes of animals; found out Fish, Frogs, Salamanders (Note:  reptiles)  CAN’T ADJUST
• while  Kittens, Monkeys, Humans (Note: mammals) ADAPTED
• Expereinces, assumptions, and expectations give us Perceptual set: mental set up to perceive one thing and not another; ufo-looking objects that are really clouds; because can’t resist finding a pattern on unpatterned stimuli
• Much of our perception comes not just from world “out there”, but also from behind the eyes and between the ears

ESP

• 50% of americans believe in extrasensory perception (ESP): claim perception occurring without sensory input
• Parapsychology: study of paranormal phenomena (profession called Parapsychologists)
• Three varieties of ESP: Telepathy (sending or reading thoughts), Clairvoyance (perceiving an event unfolding), Precognition (seeing future)
• Vague predictions can later be interpreted to match events; Nostradamus claimed his prophecies could not be interpreted till after the event
• After many experiments, never had a reproducible ESP phenomenon or individual who can convincingly demonstrate psychic ability

 
Bibliography

Myers, David G., Psychology Fifth Edition. Worth Publishers, Inc. New York, NY ©1998