Perception notes

• What is perception?• What’s Gestalt mean?• What are Gestalt’s 5 principles?• What is figure ground?• How do we perceive depth?• What are monocular cues?• What are perceptual sets?• What is the Phi phenomenon?• What’s the Muller Lyer illusion?

• The previous picture “moves” because of tiny muscular movements of your eyes.

Perception

The process of organizing and interpreting information, enabling us to recognize meaningful objects and events.

What is a Perceptual Set?

• A mental predisposition to perceive one thing and not another.

• Based on top down processing

Kiss the Guy

Perceptual Set• We perceive by filling

the gaps in what we sense.

• I _ant ch_co_ate ic_ cr_am.

• Based on our experiences and schemas.

• If you see many old men in glasses, you are more apt to process a picture of an old man (even when you may be in error).

What you see in the middle depends on your perceptual set.

Real World Application

• Cops who chase an African American suspect down a dark alley are more likely to perceive him as holding a gun than a cell phone or wallet.

• We see what we expect to see!!

When you first read this, what does it say--A When you first read this, what does it say--A Bird In The Bush? If you read this more Bird In The Bush? If you read this more carefully you will find that it says A Bird In The carefully you will find that it says A Bird In The The Bush!!! If you caught it the first time, The Bush!!! If you caught it the first time, good for you, but I bet you you did not catch it good for you, but I bet you you did not catch it this time!!!this time!!!

Gestalt Psychology• Gestalt means “an organized whole”• These psychologists emphasize our

tendency to integrate pieces of information into meaningful wholes

Gestalt Philosophy

The whole is greater than the sum of its parts

Figure Ground Relationship

Our first perceptual decision is what is the image is the figure and what is the background?

Figure-Ground Relationship

• The organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Figure ground

Camouflage works due to our inability to distinguish figure

from ground

Reversible figures: you canreverse the figure and the ground

Figure-ground principle:

states that we organize our perceptions into figure (focus or appearance of solidity) and background (not clearly shaped or patterned)

The images are exactly the same except for the thick black area in the right image (an example of the Poggendorff illusion (1860)). In the figure on the right, there appear to be two continuous diagonal lines: a red and a blue line. Which Gestalt principle explains this?

Proximity

Similarity

Closure

Gestalt and attention… Aoccdrnig to a rscheearch at

Cmabrigde Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a word are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can still raed it wouthit porbelm. This is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the word as a wlohe.

Visual Capture

• The tendency for vision to dominate the other senses.

Depth Perception• The ability to see objects in three

dimensions although the images that strike the retina are two dimensional.

• Allows us to judge distance.

Depth Cues• Eleanor Gibson and her

Visual Cliff Experiment.• Finding: depth perception is

innate (to some degree)• We see depth by using two

cues that researchers have put in two categories:

• Monocular Cues• Binocular Cues

How do we transform two-dimensional objects to three-dimensional

perception?

• Binocular Cues: depth cues that depend on two eyes

•Monocular Cues: depth cues that depend on one eye

Binocular Cues

• Retinal Disparity: a binocular cue for seeing depth.

• The closer an object comes to you the greater the disparity is between the two images.

Pen together two eyes- try with one

Monocular Cues (one eye only)

• Interposition: (overlap) if something is blocking our view, we perceive it as closer.

•Relative Size: if we know that two objects are similar in size, the one that looks smaller is farther away.

•Relative Clarity: we assume hazy objects are farther away.

More Monocular Cues• Texture Gradient: the coarser it looks the

closer it is.•Relative Height: things higher in our field of vision, they look farther away•Relative Motion: things that are closer appear to move more quickly.

•Linear Perspective: Parallel lines seem to converge with distance.

•Light and Shadow: Dimmer objects appear farther away because they reflect less light.

Linear perspective: We judgeDistance by an object’s placementBetween lines. We assume the top line is further away and longer than the bottom line because our mind perceives the railroad tracks as the same width apart.

• Texture gradient

• Relative height

Light and shadow

Size Constancy

Do you see:1. interposition?2. Relative size?3. Relative clarity?4. Relative height?5. Linear perspective

Which balloon is closer?

Relative clarity: things in the distance are fuzzier (like texture gradient)

• Identify: Interposition, Relative Size, Visual Acuity,

Linear Perspective, Texture Gradient

Motion Perception

• We perceive motion incredible well.

• We judge mostly by the size of the object.

Think about how cartoons work.

Phi Phenomenon

• An illusion of movement created when two or more adjacent lights blink on and off in succession.

Perceptual Consistency• Perceiving objects as unchanging even as

illumination and retinal images changes.• Shape constancy

Perceptual Interpretation

Context Effects

• Based on immediate context, not schemas.

• You do not hear the word, but can guess at it based on the context it was said in.

True or False?True or False?

Both center patches are the same shade of gray

True: The patch on the right appeared darker due to perceptual contrast with its background

True: The patch on the right appeared darker due to perceptual contrast with its background

Depth Perception Cues:

Motion Parallax

Visual Texture

Binocular Disparity

Perceptual Constancies

Size constancy

Space constancy

Color constancy

• 1.If you stand in the middle of a cobblestone street, the street will look coarse near your feet and finer if you look into the distance. This is called

• a.texture gradient.

• b.linear perspective.

• c.relative size.

• d.relative motion.

• 2. When traveling in a car, near objects seem to move past you faster than distant objects. This is called

• a.aerial perspective.

• b.linear perspective.

• c.relative size.

• d.relative motion.

• 3. Illusions are

• a.distortions of existing stimuli.

• b.the same as hallucinations.

• c.the result of innate mechanisms.

• d.not based on external reality.

• 4. The fact that objects that are near each other tend to be grouped together is known as

• a.closure.

• b.continuation.

• c.similarity.

• d.proximity.

• 5. The tendency to group together objects that are the same size, shape, color, or form is known as

• a.closure.

• b.continuation.

• c.similarity.

• d.nearness

• 6. As a door opens toward you, you perceive it as a rectangular door rather than going through actual image changes on the retina (from rectangular to trapezoid). This is an example of

• a.perceptual closure.• b.shape constancy.• c.ambiguous stimuli.• d.retinal disparity

• 7. Closure, nearness, similarity, and continuation are categories of

• a.perceptual (Gestalt) organization.

• b.cognitive style.

• c.cognitive organization.

• d.perceptual integration

• 8. The tendency to fill in gaps in the perception of a figure is called

• a.sensory completion.

• b.closure.

• c.figure-ground.

• d.continuation

• 9. You observe two cars of identical make and model. Although one roars away and its image on your retina is changed, you still perceive the cars as identical. This phenomenon is

• a.size constancy.• b.shape constancy.• c.concept constancy.• d.form constancy

• 10. Interposition is the pictorial depth cue more commonly known as

• a.relative motion.

• b.overlap.

• c.linear perspective.

• d.motion parallax.

• 11. A cheetah (escaped from a zoo) scrambling up a rocky slope in Montana is likely to be perceived as a mountain lion because

• a.perception is guided by expectations.

• b.figure and ground have been confused.

• c.contiguity is a powerful influence on perception.

• d.the setting provides an ideal camouflage

• 12. A widespread increase in the reported sightings of UFOs following newspaper reports of similar sightings may be attributed to

• a.perceptual defense.

• b.coordinated perceptual set.

• c.mass hallucination.

• d.perceptual expectancy. 

• 13. Assembling sensations into usable patterns is called

• a.attention.

• b.evaluation.

• c.habituation.

• d.perception

• 14. Figure and ground can be switched in

• a.shape perception.

• b.depth perception.

• c.reversible figures.

• d.nonlinear figures.

• 15. The film Star Wars created illusions of depth by quickly changing images of the sizes of planets and starships using the pictorial depth cue called

• a.convergence.

• b.accommodation.

• c.linear perspective.

• d.relative size.

• 16. Experiments with the visual cliff show that

• a.human infants are aware of shape constancy.• b.human and animal depth perception is entirely

learned.• c.perceptual grouping does not begin until a

baby is from six to fourteen months old.• d.human infants perceive depth by the age of six

months.

• 17. Motion parallax

• a.is not enough, alone, to indicate depth when most other cues fail.

• b.refers to the illusion that distant objects move slightly against a background, while closer objects move a sizable distance.

• c.is responsible for motion sickness.

• d.is dependent on stereoscopic vision

• 18. The ability to identify the direction from which a sound originates is strongly dependent on having two ears separated in space by several inches. The ability to perceive visual depth is related to a similar property known as

• a.accommodation.• b.aerial perspective.• c.retinal disparity.• d.inverted vision.

• 19. In making a charcoal pencil drawing, which pictorial depth cue could you most effectively use?

• a.accommodation

• b.retinal fusion

• c.convergence

• d.light and shadow

• 20. Perception is a process by which

• a.environmental stimuli are sensed.• b.sensations are assembled into meaningful patterns

that represent external events.• c.sensations and experiences are stored permanently in

the brain.• d.many different forms of stimulus energy are converted

into electrical signals for use by the nervous system.

A hallucination is when you see something that isn’t there. An illusion is a distortion of the senses.

*We may see an illusion because we know what we are supposed to see, even though part of a picture ordesign may not be completely there”

…when perception overrides sensation