PERCEPTUAL DEVELOPMENT
• Focus on visual perception because we know more than
other areas of perception
• Also, a major source of new information is visual
• Most major changes occur in the first year of life
PERCEPTUAL DEVELOPMENT
•We will discuss:
• Methods
• Visual Acuity
• Color and Depth Perception
• Pattern and Object perception
• Selective Attention (?)
Methods • Infants do not talk so are not able to tell us what they
see
• Must develop methods to assess what they are seeing
Methods
• Looking Paradigms
• Preferential Looking
• Present two stimuli simultaneously
• Measure the infant’s preference for one or the
other stimulus - percentage of total time looking
at one or the other
Methods
•Preferential Looking
•Requires a spontaneous preference on the
part of the infant
•Example: Visual Acuity
60%
40%
Methods
•Looking
•If infant does not have a spontaneous
preference
•Infant tends to look at a novel stimulus
over a familiar
Methods
•Habituation:
•Familiarize to one stimulus
and test with a different
one
12
10
8
6
•Measure looking time to
stimulus during
habituation and test
4
2
0
1 2 3 4 5 6 7 8 9
Methods change stimulus
•Habituation:
11.0
•If infant can
discriminate test
from familiar they
should
dishabituate
dishabituation
9.9
8.8
7.7
6.6
5.5
habituation
4.4
3.3
2.2
1.1
0
1
2
3
4
5
6
7
8
9 -1 -2 -3 -4
Methods
•Novelty-Preference
•Has components of preferential looking
and habituation
•Familiarize to initial stimulus like in
habituation
•Test is similar to preferential looking
Methods
• Habituation
• Familiarize to criterion - 50%
decrease in looking
• Present number of
familiarization trials
• 1 stimulus presented at test
• 2 stimuli presented at test -Novel & Familiar
• Compare test performance to
pre-test performance
• Compare test performance of
each stimulus to each other
Methods
•Visual Scanning and Eye
Movements
•Where the infant is looking
•How fast the infant looks
Salapatek (1968)
Methods
•Reaching
• Mostly used in depth
perception studies
• Infants will reach for the nearer
of two objects
• Visual Evoked
Potentials (VEP)
• Electrodes are placed on
infant’s head
• First, present grey field
• Then present pattern
• Get response if can
discriminate pattern
Basic Visual Functioning: Visual Acuity
• Tested with preferential
looking and VEP
• VEP gives better acuity
measures than looking
Preferential Looking
1,020
920
820
720
620
• Trend is the same,
however
520
420
320
220
Adult
120
20
0
1
2
3
4
5
6
Basic Visual Functioning: Visual Acuity
• Tested with preferential
looking and VEP
VEP
1,020
• VEP gives better acuity
measures than looking
920
820
720
620
• Trend is the same,
however
520
420
320
220
Adult
120
20
0
1
2
3
4
5
6
Basic Visual Capacities:Visual Acuity
•Acuity levels off after 6 mos. and
reaches adult level by 1 year
Basic Visual Functioning: Acuity
•What accounts for
their development?
• Cone density in fovea
is 1/3 of adult’s
1 mo cone density
• Cone length is 1/10 of
adult’s
6 mo cone density
Color Perception
•Contrary to myth, newborns see color
•Preferential looking experiment with 1- to 5day-olds
•Colors were either red, green, yellow, or blue
Color Perception
•Newborns could see red, yellow, and green
•Newborns could not see blue
•Adult-like color perception develops by 3 - 4
months of age
Depth Perception
• Binocular Cues
• Young infants have difficulty coordinating the two eyes
early on
• Binocular Disparity
• Aslin - moved a target between a near (12 cm) and a far
point (57 cm)
• Found that some binocular fixation occurs at 1 and 2 months
• Reliable fixation does not occur before 3 months
Depth Perception
•Richard Held
measured infants’
preferential looking to
one stimulus that had
depth and one that
did not.
Depth Perception
• If infants can see the
binocular disparity, then will
look longer at stimulus on
the left
• Found that infants do not
use disparity until
approximately 3.5 months
Depth Perception
• Monocular Cues
• Interposition (or occlusion): One object is in front of
another and occludes part of the one behind
• Size: Objects that are closer appear larger
Depth Perception
•Granrud & Yonas
• Used a reaching paradigm and the stimuli: interposed and not
interposed
• If infants can use interposition, then should reach for
interposed more than non-interposed
(a)
(b)
(c)
Depth Perception
•Granrud & Yonas
•Found that 7-month-olds but not 5-montholds reached for the occluded display (a)
(a)
(b)
(c)
Depth Perception
•Size - Granrud, Hoake, & Yonas
• Used reaching
•The member of the test pair that is larger than
in familiarization should be perceived as closer
Familiarize
Test
Depth Perception
•Size - Granrud, Hoake, & Yonas
• Used reaching
•Found that 7-month-olds but not 5-month-olds
reached for the apparently closer object
Familiarize
Test
Object Perception
•Illusory Contours
Object Perception
• Bertenthal, Campos, and Haith - used habituation
• Found that 7-month-olds but not 5-month-olds
dishabituated to a change between illusory and nonillusory
Object Features and Feature Relations
•When do infants see
a whole form?
•Salapatek measured
infants’ visual
scanning of triangles
1-month-old
2-month-old
Pattern, Shape, & Object Perception
• When do infants perceive whole forms?
• Cohen & Younger (1984), using habituation, tested line
orientation versus overall form discrimination
Habituate
Change Form Test
Change Orientation
Test
Pattern, Shape, & Object Perception
• Found that 6-week-olds discriminate an orientation but
not a form change
• 3-month-olds discriminate a form change
Habituate
Change Form Test
Change Orientation
Test
Object Perception
• Do infants perceive unitary objects?
• Kellman & Spelke (1983)
Habituate
Unitary Object Test
Two Object Test
Object Perception
•4-month-olds perceive a unitary object, but
only when the rod moved
Habituate
Unitary Object Test
Two Object Test
Pattern, Shape and Object Perception
• Summary
• 2-month-olds could see the whole form
• 3-month-olds perceived a whole form
• 4-month-olds perceived a whole form even when they could not see
the whole form
Selective Attention
• Visual Pop-Out
• Stimuli with a unique property jump out from the
surrounding environment and capture our attention
• Sireteanu & Rieth vs. Atkinson & Braddick (1992) used preferential looking to assess pop-out in infants
Selective Attention
• Sireteanu & Rieth found that 10 to 12-month-olds
exhibited pop-out
• Atkinson & Braddick found that 3.5 to 4.5-month-olds
exhibited pop-out
Selective Attention
Infant
B
650
J
Saccade Latency
600
J
J
B
400
350
J
J
500
B
B
B
600
Five
Eight
J
J
400
350
250
Set Size
Target
Absent
J
450
250
Three
J
500
300
One
Target
Present
550
300
200
B
650
Target
Absent
550
450
700
Target
Present
Saccade Latency
700
Adult
200
J
B
B
B
Three
Five
Eight
B
One
Set Size
•Recently, Adler & Orprecio (2006), using eye
movements, have found that infants exhibit
pop-out similar to adults