Perception

How we organize and interpret sensory information

Inattentional Blindness

When focusing on one thing, we often miss or ignore other stimuli (no matter how exaggerated or crazy the stimuli may be… for example the gorilla in the basketball game).

Selective attention - we can only focus awareness on a limited part of what we are sensing.

Cocktail party effect – type of selective attention in which you can attend to only one voice at a time

Cell phones and driving? Listening to music and studying?

Visual Capture

The tendency for vision to dominate your senses.

At an IMAX movie, it feels like you are moving because it looks like you are moving. Your vision dominates over your vestibular system.

Parallel processing – processing many things at once

Man who mistook his wife for a hat – could see form but not the big picture

Colorblindness with functional conesMotion blindnessBlindsight

Perceiving Images

The first step in perceiving an image is determining the figure and ground.

The Gestalt Principles

Gestalt and the Urge to Organize

Gestalt and the blind spot

Other gestalt principles

More gestalt

And more gestalt

Depth Perception (seeing in 3D)Depth Perception (seeing in 3D)

Binocular cues – require both eyes

Retinal disparity – cue for relative distance of

different objects (greater the disparity, the

closer the object)

Convergence – extent to which eyes converge

inward when looking at something (greater

inward strain, the closer it is)

Depth Perception (cont’d)Depth Perception (cont’d)Monocular cues (available to each eye separately)

Relative size – assuming two objects are the same size, the one casting a smaller retinal image is farther away

Interposition – object partially blocking view of another perceived as closer

Relative clarity – hazy objects perceived as farther away than sharp, clear objects

Texture gradient – gradual change from coarse, distinct texture to a fine, indistinct texture signals increasing distance

Depth Perception (cont’d)Depth Perception (cont’d)Monocular cues (cont’d)

Relative motion (motion parallax) – as we move, objects that are stable appear to move. The nearer the object, the faster it appears to move. Objects beyond fixation appear to move with you.

Linear perspective – parallel lines appear to converge with distance.

Light and shadow – Nearby objects reflect more light on our eyes. Dimmer ones seem farther away. (Janus’ mask… assume light comes from above, so location of shadow indicates whether objects are concave or convex)

Motion PerceptionHow does the brain recognize an object is moving? How does it interpret the direction of

movement?

Brain interprets shrinking objects as receding and enlarging objects as approaching

Stroboscopic Effectthe perception of motion produced by a rapid succession of slightly varying images (animation, movies)

Phi phenomenonan illusion created when two or more adjacent lights blink on and off in succession, creating the perception of movement (lighted signs, illusions)

Motion Perception

Objects that are farther away appear to be moving more slowly. Think of a plane in the sky or a truck in the distance

Perceptual Constancy - the ability to perceive an object is the same even as the illumination and retinal image changes.

Shape Constancy – perception that shape of an object doesn’t change just because image on the retina does.

How many right angles do you see?

Perceptual Constancy

Size constancy – perception that an object’s size remain the same even as the retinal image changes.

Color Constancy – the perception that familiar objects have a consistent color, even if changing illuminations alter the wavelength reflected.

What color are the squares indicated by arrows?

Don’t believe me….? Watch this!

Perceptual Constancy

Lightness constancy – the perception that familiar objects have a constant lightness, even while illumination varies.

Size-distance relationshipWhen other monocular cues tell us an image is further away, it actually appears larger.

Moon illusion

Imagine you are outside on a clear night in which there are no clouds and that is a bright full moon. Pretend that you are going to pick up one of the following objects that when held at arm’s length just covers up the moon.

Moon Illusion Objects Imagine the moon is straight overhead.

BB

Pea

Dime

Penny

Nickel

Quarter

Golf ball

Baseball

Softball

Small Salad Plate

Large Salad Plate

Frisbee

Basketball

Beach ball

Moon IllusionNow imagine the horizon moon.

Softball

Small Salad Plate

Large Salad Plate

Frisbee

Basketball

Beach ball

BB

Pea

Dime

Penny

Nickel

Quarter

Golf ball

Baseball

Moon Illusion

What object do you need?

A pea! For both the overhead and horizon moon.

Muller-Lyon IllusionWhich is longer?

Muller-Lyon Illusion

Perceptual Adaptation

What happens if you wear goggles that distort your world? Could you shake hands? Catch a ball?

Let’s try!!

Perceptual Set – like a mental predisposition

Looking at either the left or the right-hand image first is likely to cloud your perspective of the center, ambiguous figure.

Perceptual Set ExamplesPunctuate the following so it makes sense:

TIME FLIES I CANT THEYRE TOO FAST

Read the following words out loud as they appear:MacDonaldMacHenryMacMurrayMachinery

Now let’s try some more…

Unscramble in order.

List A List B

LULB

CALEM

NUKKS

SEUMO

BAZER

EAP

NORC

NOONI

MATOOT

PREPPE

TEBE

EAP

In the next slide you will see a picture of two people. Name the person standing on the left (slightly behind the other person).

Context Effects

Who was it?

Let’s take another look…

Extrasensory Perception

Telepathy – mind readingClairvoyance – perceiving remote eventsPrecognition – Knowing things before they

happenTelekinesis (psychokinesis) – moving

objects with one’s mind (not technically ESP)