Perception

How we organize and interpret sensory information

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.

Perceiving Images

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

Do you see the arrow?

Gestalt and the Urge to Organize

Other gestalt principles

Simplicity

Gestalt Principles: Closure

Gestalt Principles: Continuity

Gestalt Principles: Proximity

Gestalt Principles: Similarity

Gestalt and the Lion King

http://www.youtube.com/watch?v=skD2gyP1cCshttp://www.youtube.com/watch?v=zdtMTixlBFI

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)Stroboscopic effect

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

Perceptual Constancythe 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 (the incredibly shrinking teacher) – perception that an object’s size remain the same even as the retinal image changes.

Perceptual Constancy

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

Perceptual Constancy

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

Visual Cliff – used to check for depth perception.

Pre-Renaissance Art

The Holy Innocents by Giotto di Bondone.Jesus on Way to CalvarySimone Martini

Masaccio, Trinity (ca. 1425).

Leonardo Da Vinci, The Last Supper

Renaissance Art

Depth Perception Monocular Depth Cues

Linear perspective (parallel lines appears to converge on a vanishing point)

Relative height (more distant objects are higher)

Relative size (more distant objects are smaller)

Depth Perception

Monocular Depth CuesRelative clarity (objects in

the distance appear hazy)Overlap/interposition

(continuous outlines appear closer)

Depth Perception

Monocular Depth CuesTexture gradient (texture

details, like roughness, diminish with distance)

Depth Perception

Monocular Depth CuesLight and shadow

How many can you identify here?

Depth Perception

Monocular Depth CueMotion parallax (or relative motion) – Distant

objects will appear slow in comparison with close objects even when the two are moving at the same speed

Think of an airplane traveling overhead.http://www.youtube.com/watch?v=-

OmK3rGk__I&NR=1

Depth Perception

Binocular depth cues – require two eyesRetinal disparity – the greater the difference

between the images on your two retina, the closer the object (“camera 1, camera 2”, “finger sausage”, hole in the hand)

Convergence – the greater your eye muscles must strain (or converge) to focus on an object, the closer the object (notice how hard your eyes strain when you focus on the tip of your nose).

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

Horizon Moon

High moon on a clear night.

Muller-Lyon IllusionWhich is longer?

Muller-Lyon Illusion

Perceptual Set

Perceptual Set

Perceptual Set

Context Effects

Extrasensory Perception

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

happenTelekinesis (psychokinesis) – moving

objects with one’s mind (not technically ESP)