Chapter 6Perception

Perception

Selective Attention: focus of conscious awareness on a particular stimulus

Cocktail party effect

Cocktail party effect explains your ability to keep your attention on only one voice in a room even if there are many other people talking in the room at the same time.

This ability to keep your attention can be altered though if someone says your name.

This guy

Paying attention to only this girl

Even though all these people are talking

Until this woman(?) says his name

Then his attention is on her (?)

Awareness Test Video

How many times does the team in white pass the ball?

Who Done It?

Let’s test your awareness again

Change Blindness

Change Blindness video

NOVA videoExperiment video

Perceptual Illusions

the Müller-Lyer illusion

Experiments proved that African tribes who lived in villages composed of only round huts were not fooled by the Müller-Lyer illusion

• These findings suggest that individuals in the United States are fooled by the Müller-Lyer illusion because we have developed ways of judging depth based on what we are used to seeing.

• We are used to seeing outside corners of buildings as near to us with the top and bottom of the corner sloping out and away

Perceptual Illusions

Perceptual Illusions

Perceptual Illusions

Perceptual Illusions

Perceptual Organization: Gestalt

Visual Capture– tendency for vision to dominate the other

senses–Ventriloquist doll

S M OTHER I N G

Gestalt--an organized wholetendency to integrate pieces of information into meaningful wholes

Perceptual Organization: Gestalt

Groupingthe perceptual tendency to organize stimuli into

coherent groupsGrouping 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

Perceptual Organization: Grouping Principles

Perceptual Organization: Closure

Perceptual Organization

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

Figures = words

Ground = white page

Which is the figure and which is the ground?

While the figure continuously reverses between walking people and directional arrows, we will always see those to figures as being separate from the ground (both the black on the bottom and the white on the top.

Perceptual Organization: Depth Perception

Depth Perception– ability to see objects in three dimensions– allows us to judge distance

Binocular cues- both help with judging distance (depth perception)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

– The more your eyes have to move inward towards one another, the closer the object must be to your face

Perceptual Organization: Depth Perception

Visual Cliff

Retinal disparity You can try this yourself

Because your retinas are separate from one another and about 2 ½ inches apart, they will see images slightly differently, especially when the images are closer to your eyes

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 --> closefine --> distant

Perceptual Organization: Depth Perception

Relative Size

Interposition

Which king is closer?

This guy

Interposition confusion

Relative Clarity

The boat is more clear, so it must be closer

Texture gradient Objects that are further away seem to be much

more densely with finer details, while closer objects have much more bold and coarse details.

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

Perceptual Organization: Depth Perception

Relative Height- lower buildings seem closer

Relative motion

Video- which appears to be moving faster, the batteries or the shoe?

Perceptual Organization: Depth Perception

Light and Shadow- used to create the idea of depth

Perceptual Organization: Depth Perception

Perspective Techniques-light and shadow are used to create an idea of depth

Motion Perception

Phi phenomenon- when two adjacent stationary lights blink on and off in quick succession, we perceive a single light moving back and forth between them.

Perceptual Constancy-perceiving objects as unchanging even as

illumination and retinal image change-The door looks increasingly like a trapezoid, but we still perceive it as a rectangle

• color• shape • size

Perceptual Constancy

Size-Distance Relationships

Ponzo Illusion

Perceptual Organization: Muller-Lyer Illusion

Perceptual Illusions

Perceptual Organization: Size-Distance Relationship

The moon illusion

Try this: at what point does the moon seem larger, when it is on the horizon line or when it is high up in the air?

The moon will seem up to 50 percent larger when it is lower in the sky at the horizon. One theory for why this is suggests that the moon seems larger because it is directly behind trees and buildings that you can compare its’ distance with.

Lightness constancy

Lightness constancy- we perceive things to have a constant lightness even while it’s illumination varies.

Lightness constancy depends on an objects relative luminance, which is the amount of light an object reflects relative to its’ surroundings.

Perceived lightness stays roughly constant, given an unchanging context. But when the surrounding context of an object changes, the perceived lightness will change with its’ surroundings. This phenomenon can be used to create illusions.

Perceptual Organization-Brightness ContrastWhich square is a lighter color, A or B?

Believe it or not, both squaresare the same exact color!

Sensory Deprivation:Blakemore & Cooper, 1970

Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.

Perceptual Interpretation

Perceptual Adaptation-(vision) ability to adjust to an artificially

displaced visual field•prism glasses

Perceptual Set-a mental predisposition to perceive one

thing and not another

We see familiar images on Mars because we are used to seeing these images.

Perceptual Set: Schemas

What you see in the center is influenced bythe perceptual set

What do you see, a saxophone player or a woman's face?

You will be much more likely to see a woman’s face if first you look at the unambiguous picture of the woman’s face at the bottom.

Perceptual Set: Schemas

Flying Saucers or Clouds?

Perception and the Human Factor

Human Factors Psychology• explores how people and machines interact• explores how machine and physical environments can be

adapted to human behaviors

Perceptual Set: Human Factors

Actualdescent

path

Pilot’s perceiveddescent path

Altitude looksthis much higher

20 18 16 14 12 10 8 6 4 2Distance from runway (miles)

10

8

6

4

2

0

Altitude(thousands

of feet)

Is There Extrasensory Perception?

Extrasensory Perception-controversial claim that perception can occur apart from

sensory input• Telepathy- communicate thoughts from one mind to another• Clairvoyance- sixth sense of seeing things outside of normal

world vision• Precognition- direct knowledge of the future

Parapsychology-the study of paranormal phenomena

• ESP• psychokinesis

Telepathy

Precognition

Clairvoyance

Clairvoyance

Are you clairvoyant? http://www.psychicguild.com/esptest/