Pop-Out Phenomenon

When a strikingly distinct stimulus, such as the only smiling face, draws our eye.

Perceptual Sets The tendency for our perceptions to be

influenced by expectations or preconceptions.

A mental predisposition that greatly influences what we see. Devoted fans to science fiction are

more likely to see UFO’s We may fail to notice writing and

printing errors. Have also found that emotion,

motivation and culture can influence our perception.

Is this the letter B or the number 13?

The cat sat on the map and licked its whiskers.

Perceptual Set

What you see in the centre figures depends on the order in which you look at the figures: If you scan from the left, see an old woman If you scan from the right, see a woman’s figure

Schemas Through experience we form concepts, or schemas,

that organize and interpret unfamiliar information. Especially strong are out schemas for faces.

Mona Lisa

Form Perception Gestalt principles describe the brain’s

organization of sensory building blocks into meaningful units and patterns.

They generated laws of perceptual organization such as: Figure and Ground Laws of Grouping

Figure and Ground Organization of the

visual field into objects (figures) that stand out from their surroundings (ground).

Gestalt Laws of Grouping

Proximity: Objects that are near each other will be perceived as belonging to a common set. Seeing 3 pair of lines in A.

Similarity: Objects that are similar will be perceived as belonging to the same group. Seeing columns of orange

and red dots in B.

Gestalt Laws of Grouping

Continuity: Tendency to perceive stimuli in a unified form. Seeing lines that

connect 1 to 2 and 3 to 4 in C, rather than four separate lines.

Gestalt Laws of Grouping Closure: Grouping disconnected

pieces into a meaningful whole. Seeing a horse in D and

“triangle.” Connectedness: The tendency to

perceive objects as belonging together when they are positioned together or are moving together.

Form Grouping

Impossible Doghouse

Depth Perception

Seeing objects in three dimensions enables us to determine distance.

Visual Cliff experiments

Gibson and Walker

Visual Cliff A laboratory device for testing depth perception in

infants and young animals. It suggests that the ability to perceive depth is at

least partially innate.

Binocular Cues Visual cues to depth or

distance that require the use of both eyes. Retinal Disparity: The slight

difference in lateral separation between two objects as seen by the left eye and the right eye.

Convergence: Turning inward of the eyes, which occurs when they focus on a nearby object. The more the inward strain

the closer the object.

Monocular Cues

Relative Size: The one that casts the smaller retinal shadow is further away.

Monocular CluesInterposition: if one object partially blocks another we perceive it as closer.

Interposition

Monocular Clues Relative Clarity: We perceive hazy objects as

farther away than sharp focused ones.

Monocular Clues Texture Gradient: A gradual change from a coarse, distinct texture to

a fine, indistinct texture signals increasing distance.

Monocular Clues Relative Height: We perceive objects higher in our field

of vision as further away.

Monocular Clues

Relative Motion: As we move, objects that are actually stable appear to move. The nearer the object the faster

it seems to move.

Monocular Clues Linear Perspective: Parallel

lines appear to converge with distance.

Monocular Clues Light and Shadow: Nearby objects reflect more light

into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away.

In or Out?

Distance CuesThe moon just above the horizontypically appears to be unusuallylarge because we perceive it asunusually far away from ourselves.This is a result of distance cues,which make the horizon moonseem farther away. The horizonmoon appears to shrink in size if itis viewed through a narrow tubethat eliminates the perception ofdistance cues. This illustrates theimportance of context effects.

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. An illusion of movement

Motion Perception Objects traveling

towards us grow in size and those moving away shrink in size.

The same is true when the observer moves to or from an object.

Perceptual Constancy Perceptual constancy enables us to perceive an object as unchanging

even though the stimuli we receive from it change. Thus, we can identify things regardless of the angle, distance, and

illumination by which we view them. Constant in terms of color, size and shape

Shape Constancy Even though these images cast shadows of

different shapes, we still see the quarter as round

Size Constancy We perceive objects as having a constant size,

even while our distance from them varies.

Lightness Constancy

We perceive an object as having a constant lightness even while its illumination varies.

Perceived lightness depends on relative luminance. The amount of light an

object reflects relative to its surrounding.

The Ames Room

The Ames Room

The Ames Room A specially-built room

that makes people seem to change size as they move around in it

The room is not a rectangle, as viewers assume it is

A single peephole prevents using binocular depth cues

Visual Illusions

Illusions are valuable in understanding perception because they are systematic errors. Illusions provide hints about perceptual strategies.

In the Muller-Lyer illusion (above) we tend to perceive the line on the right as slightly longer than the one on the left.

The Ponzo Illusion Linear perspective

provides context Side lines seem to

converge Top line seems

farther away But the retinal

images of the red lines are equal!

Fooling the Eye

The cats in (a) are the same size The diagonal lines in (b) are parallel You can create a “floating fingertip frankfurter” by holding

hands as shown, 5-10” in front of face. Look beyond your fingers to experience the illusion.

Hearing:The Psychology of Sound Sound waves are really air

molecules being pushed about. Frequency: The length of the

sound wave. Pitch

Amplitude: The height of the sound wave. Loudness

Timbre: Complexity of sound, mixtures of tones Allows us to recognize a

friends voice on the phone.