infant perception. william james, 1890 “the baby, assailed by eyes, ears, nose, skin and entrails...
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Infant Perception
William James, 1890
“The baby, assailed by eyes, ears, nose, skin and entrails all at once, feels it all as one great blooming, buzzing confusion.”
Infant Vision
• Infants’ looking is:– active– organized– selective
• They prefer stimuli with:– high contrast– curves– motion
babies LOVE faces!
Fantz’ Methodological Breakthrough:Preferential Looking Paradigm
• Infants view two simultaneous displays.
• Measure their looking time to each display.
• If infants consistently look longer at one than the other, then they can discriminate between the two displays.
* Preferences logically imply discrimination *
Visual Acuity
A:
B:
Visual Acuity
• Newborns: 20/200 to 20/400
(legally blind)
• 3-month-olds: 20/100
• 6-month-olds: 20/70
• 1-year-olds: Close to adult level
Habituation/Dishabituation Paradigm
• Show same thing repeatedly until infants get bored (decreased looking)
• Show new thing and measure looking
Using Habituation/Dishabituationto Test Infants’ Color Perception
Color => Wavelengths of light; a continuous dimension
Categorical Color Perception
480 nanometers = “BLUE”
510 nanometers (+ 30) = “GREEN”
450 nanometers (- 30) = “BLUE”
Physical Level Psychological Level (continuous) (categorical)
450 480 510
Categorical Color Perception in 3-month-old Infants
Habituation Phase:• Infants are habituated to one wavelength
(480; “blue”)
Test Phase:• Group 1 views wavelength of + 30 nm
(510; “green”)
• Group 2 views wavelength of - 30 nm (450; “blue”)
Categorical Color Perception in 3-month-old Infants
Results:
• Infants who view wavelength that crosses color boundary dishabituate
Conclusion:
• Infants perceive colors in categories, much like adults do
Rules that Babies Look ByMarshall Haith
1. If awake, open your eyes.
2. If in darkness, search around.
3. If find light, search for edges.
4. If find edges, examine them.
Visual Scanning
• 1-month-olds: scan perimeter of an object/face (highest contrast with background)
• 2-month-olds: scan more broadly, both outer edges and inner detail
Infants’ Auditory Sensitivity
• Pretty good!
• Decrement of ~10 decibels
• Most sensitive to sounds of human speech
At birth, babies recognize and prefer their mothers’ voice
Categorical Speech Perception
• Speech sounds are perceived in distinct phonemic categories
• Example: /ba/ vs. /pa/
• Produced in the same way; only difference is Voice Onset Time
Categorical Speech Perception in 1-month-old Infants
GROUP 1Habituation Phase:Repeated exposure to
VOT: 20 msec = /ba/
Test Phase:Presentation of new
VOT: 40 msec = /pa/
GROUP 2Habituation Phase:Repeated exposure to
VOT: 60 msec = /pa/
Test Phase:Presentation of new
VOT: 80 msec = /pa/
For both groups, the acoustical difference between sounds is the same (+20 msec)
Categorical Speech Perception in 1-month-old Infants
Results:
• Infants who hear VOT that crosses category boundary (Group 1) dishabituate
Conclusion:
• Infants can distinguish phonemic sound categories
Categorical Speech Perception
• 1-month-olds can discriminate all sound categories (600 consonants, 200 vowels)
• Between 6-12 months of age, this ability narrows to only those sound categories available in the infant’s native language
Music Perception
• Babies LOVE music
• Respond to rhythm (bounce, move)
• Prefer consonance vs. dissonance
• Can recognize same melody played at different pitches
In summary
Infant perception is active & organized
next time….infant cognition