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