UNIT 4B: PERCEPTION
THE BIG DEAL WITH PERCEPTION
 We know how we see, hear, touch, taste and smell.
 So… how do we not just see shape and colour, but a rose in bloom, a loved one’s face, a beautiful sunset?
 So… how do we not just hear pitches and rhythms, but a cry of pain, hum of traffic or music?
 How do we organize and interpret our sensations so that they become meaningful perceptions?
GESTALT
 When given a cluster of sensations, we tend to organize
them into a whole called a gestalt  an organized
whole. Gestalt psychologists emphasized our
tendency to integrate pieces of information into
meaningful wholes.
 Said that the whole may exceed the sum of its
parts. Ex. Combine sodium (corrosive metal) with
chlorine (poisonous gas) = Salt.
 Look at the Necker Cube. Nothing but 8 blue
circles with some white lines. What do we see as
the ‘whole’?
 Our brain does more than register information
about the world.
FORM PERCEPTION
 Part of perception is organizing, in our brains, the
perception of an object as distinct from their
surroundings.
 Figure ground  the organization of the visual
field into objects (the figures) that stand out from
their surroundings (the ground).
 Will continue to reverse in our brains, but we will
always go back to what is the figure, what is the
ground?
 Words are the figures, paper is the ground.
 Think of a few more…
GROUPING
 The figure now needs to be organized in a meaningful way.
 Grouping  the perceptual tendency to organize stimuli into coherent groups.
 Proximity
 Similarity
 Continuity
 Connectedness
 Closure
FORM PERCEPTION
GROUPING - PROXIMITY
 Group nearby figures together.
 See 3 sets of 2 lines, not 6 lines total.
FORM PERCEPTION
GROUPING - SIMILARITY
 Group similar figures together.
 We see the triangles and circles as similar vertical lines.
 We do not see 3 horizontal lines of alternating shapes.
FORM PERCEPTION
GROUPING - CONTINUITY
 Series of alternating semi-circles
 We see 2 continuous lines:
 Curved and straight
FORM PERCEPTION
GROUPING - CONNECTEDNESS
 Linked, 3 sets of 2 dots.
 Rather than 6 total dots.
FORM PERCEPTION
GROUPING - CLOSURE
 Fill in the gaps to see a complete, whole object.
 We assume the circles are blocked by an imaginary triangle.
 3rd image with lines added, now we can see the circles because your brain stops filling in the gaps.
DEPTH PERCEPTION
 We receive 2 dimensional images in our retinas, that our brains organize into 3 dimensional realities.
 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.
 Ex. Crossing the street, estimate the distance of an oncoming car.
 http://www.youtube.com/watch?v=QGNdtLZ-lGA
 Used in the visual cliff experiments  a laboratory device for testing depth perception in infants and young
animals.
 We come pre-wired to perceive depth, however, grows with age.
BINOCULAR CLUES
 With both eyes open, hold 2 pens in front of you and touch their tips together.
 Do it again, with one eye closed.
 Binocular Clues  depth cues, such as retinal disparity, that depend on the use of two eyes.
 Eyes are 2.5 inches apart, our retinas each receive their own image of the world.
 Brain will compare both images and the difference between them to help understand the relative distance between 2
objects.
 Hold your pointer fingers directly in front of your nose – both eyes open, one eye closed. What happens? Now move
them further away.
 Retinal Disparity  a binocular cue for perceiving depth. By comparing images from the retinas in the two
eyes, the brain computes distance – the greater the disparity (difference) between the two images, the closer
the object.
 Placement of eyes on head – binocular vs peripheral vision.
 3D movies, with 2 cameras placed a few inches apart. Isolates each eye, makes 3D image.
MONOCULAR CUES
 Retinal disparity is slight when looking
straight ahead.
 Rely on monocular cues  depth cues,
such as interposition and linear
perspective, available to either eye alone.
 Which is bigger, height or width?
 HA! Height and width are equal. Relative height creates this horiztonal- vertical illusion.
 Our perceiving vertical dimensions as longer than horizontal dimensions.
 Water glass demo.
DEPTH PERCEPTION
MONONOCULAR CUES
 Monocular cues – pg 155
 Relative height
 Relative size
 Interposition
 Linear perspective
 Relative motion
 Light and shadow
DEPTH PERCEPTION
RELATIVE HEIGHT
DEPTH PERCEPTION
RELATIVE SIZE
DEPTH PERCEPTION
INTERPOSITION
DEPTH PERCEPTION
LINEAR PERSPECTIVE
DEPTH PERCEPTION
RELATIVE MOTION
DEPTH PERCEPTION
LIGHT AND SHADOW
MOTION PERCEPTION
 Motion applies to writing, eating, walking, driving… etc.
 Your brain computes motion based partly on its assumption that shrinking objects are retreating ( not getting
smaller) and enlarging objects are approaching.
 Large objects (trains) appear to move more slowly and smaller objects (cars) moving at the same speed.
 Applies to trying to catch a fly ball or a dog catching a Frisbee.
 Stroboscopic movement – 24 frames per second in animation film, we construct the motion in our
heads.
 Phi Phenomenon  an illusion of movement created when two or more adjacent lights blink on and off
in quick succession.
 Marquee lights.
PERCEPTUAL CONSTANCY
 Perceptual Constancy  perceiving objects as unchanging (having consistent shapes, size, lightness, and
color) even as illumination and retinal images change.
 How can we recognize objects without being deceived by changes in their shape, size, brightness or
color.
 Top-down processing that is very fast.
 Size/Shape Constancy – objects will have a constant size, even when our distance from them varies.
Ex. We assume a car is a large object that can hold people even when it looks tiny from far away.
Connection between perceived distance and perceived size – knowing the distance away gives us clues
to it’s size, along with knowing it’s general size.
READ THIS SLIDE
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SHAPE CONSTANCY
SIZE CONSTANCIES
 Size constancy
 Moon illusion
 Ponzo illusion
AMES ROOM
AMES ROOM
LIGHT CONSTANCY
 White paper reflects 90% of light falling on it, while
black paper only reflects 10%. Put them in sunlight
and the black paper will reflect 100 times more
sunlight than the white paper, but it still appears
black.
 We perceive an object as having a constant lightness
even when it’s illumination varies.
COLOR CONSTANCY
 Color Constancy  perceiving familiar objects as
having consistent color, even if changing
illumination alters the wavelengths reflected by
the object.
 As the brightness of light chances on a apple,
still appears red.
 Our experience of color comes not just from the
object, but from everything around it as well.
 We see color based on our brain’s computations
of the light reflected by any object relative to it’s
surrounding objects.
PERCEPTUAL INTERPRETATION
 Debate on whether our perceptual abilities are influence more by nature or nurture.
 To what extent do we LEARN to perceive?
 Inborn ways of organizing sensory experiences? OR Through our experiences do we learn to perceive our world?
 Think of this experiment: A person born blind was taught through touch alone, the difference between a cube and
a sphere. If they were made to see, could they visually distinguish between them?
 The common answer is no, because the person never learned to see the difference.
 This has been put to the test in the ‘real world’ – Although their sight slightly improved, they could still, not by
sight, identify the shapes that they could by touch.
 If the change is done later on in life (ex cataracts in older humans), the eye will return back to normal.
 Critical Period
 Mike May – lost vision at age 3
 Restored while in adulthood.
 Could see wife and kids, but although the signals
were reaching his visual cortex, it had be dormant so
long that he lacked the experience to interpret them.
 Facial expressions difficult.
 Can see some movement, learning to identify sights.
 Dust in Sunlight.
PERCEPTUAL ADAPTATION

Perceptual Adaptation  in vision, the ability to adjust to an
artificially displaced or even inverted visual field.

When you get a new prescription of glasses, dizzy for a few
days, then you get used to them.

We can give people perceptional glasses that will shift their
vision 40 degrees to the left. Over time we can adjust to these
glasses and learn to function normally with them. (Ex. Throwing
a ball).

Upside down glasses, worn for 8 days. Walking, eating difficult.
Took 8 days to adjust.

As long as we wear the device long enough, we can even do
more complicated movements, like skiing or driving.

http://www.youtube.com/watch?v=-kohUpQwZt8
PERCEPTUAL SET
 Perceptual Set  a mental disposition to perceive
one thing and not another.
 Mental Predisposition – Top Down Processing
 Adult and child are perceived as looking more alike
when you are told they are parent and child.
 Fries served to children out of a McDonald’s bag
were said to taste better than the same fries served
out of a plain, white bag.
 Our perceptual set is determined by Schemas, that
organize and interpret unfamiliar information – Ex.
Seeing the face in the moon.
CONTEXT EFFECTS
 A given stimulus will trigger a radically different perceptions, due to our differing set,
but also because of the immediate context we are in.
10 inch difference between the 2 players, 6’9” and 7’9”.
 The effects of perceptual set and context show how experience helps us construct perception.
 Stereotypes about gender can color our perception. Cues of pink or blue, struggle to call a new baby ‘he’ or ‘she’,
name dictates gender.
 Culture and context effects – Figure at the top of 164.
EMOTION AND MOTIVATION
 Perception is influenced by both our expectations, as
well as our emotions/motivations.
 Ex. Walking distances look farther away to those who
have been fatigued by prior exercise.
 Ex. Hills look steeper to those wearing a heavy
backpack, or those who were exposed to sad, heavy
music, rather than light, upbeat music.
 Ex. Target looks further to those who have to throw
a heavy vs. a light object.
 Motivation – Which gets rewarded? Farm or Sea
animal? Choice influenced from then onwards.
 Emotional influences influence our social perceptions.
 Ex. Spouses who feel loved and appreciated perceive less threat in stressful martial events.
 Ex. If you inform a professional sports referee that a team has a history of aggressive behaviour, they will assign
more penalties to that team, after watching video taped footage.
 Ex. When you are driving, you hate pedestrians, but when you are walking you hate drivers.
 So is perception innate or learned? – It’s both! Fed with sensation, cognition and emotion.
Parapsychology
EXTRASENSORY PERCEPTION OR ESP
 Extrasensory Perception (ESP)  the controversial
claim that perception can occur apart from sensory
input; includes telepathy, clairvoyance and
precognition.
 Parapsychology  the study of paranormal
phenomenon, including ESP and psychokinesis.