PSYB20H3 Chap.9 Infant Senses and Perception Research Methods
Infant Senses and Perception Research Methods
What newborns can sense
The second half of Lecture 4 in PSYB20H3 surveys the senses at birth. Taste is highly developed even before birth, and by two hours of age babies distinguish sweet, sour and bitter solutions. Smell is present very early, as facial expressions show.
Touch is well developed in the womb, where a fetus grasps the umbilical cord and sucks a thumb, and after birth it is most sensitive around the mouth, palms and soles.
Hearing works during the last two months of pregnancy, newborns discriminate their mother's voice, and hearing is more developed than vision at birth.
Vision, the least mature sense
A newborn's visual acuity is 20/240: what an adult with normal vision sees at 240 feet, a newborn sees at 20. Acuity reaches 20/40 by six months and adult level by twelve months.
Even so, newborns prefer their mother's face over a female stranger's as early as twelve hours after birth. Numerical facts like these are common multiple-choice targets.
Sensation, perception and affordances
Sensation and perception differ: sensing a stimulus is not the same as interpreting it.
In Gibson's ecological view, perception exists so that people can engage with their surroundings and adapt, and objects carry affordances, opportunities for interaction perceived directly from the environment and the body.
This links perception to motor action and to the dynamic systems account of motor skills.
Three ways to study infant perception
Researchers infer understanding, preferences and expectations from observable behaviours such as heartbeat, breathing, sucking and looking.
The preference technique, from Fantz's looking chamber of 1956 to modern eye-tracking, shows two stimuli and measures which one holds attention longer. Habituation and dishabituation present one stimulus until attention falls, then switch to a new one; renewed attention shows discrimination.
The high-amplitude sucking method infers discrimination and preference from changes in sucking rate on a special pacifier.
Reading results correctly
The most common error is reading dishabituation as preference. A rebound in looking after a change shows that the infant can tell the stimuli apart, not which one the infant likes.
Another frequent item describes a study and asks for both its design and its technique, which are separate answers from Chapter 1 and from this chapter.
What this chapter covers
- 01
Taste, smell and touch at birth
- 02
Hearing before and after birth
- 03
Visual acuity in the first year
- 04
Sensation and perception
- 05
Gibson's ecological view and affordances
- 06
Preference technique
- 07
Habituation and dishabituation
- 08
High-amplitude sucking method
Worked example · free
Read a habituation graph trial by trial
- 1Looking fell from 12 to 3 seconds, a drop of 9 seconds or three quarters: habituation.
- 1The rise to 9 seconds for the circle is dishabituation, showing the infant tells the shapes apart.
- 1It does not show that the infant prefers circles, only that the circle is perceived as new.
Key terms
- Affordance
- An affordance is an opportunity for interaction that an object offers, perceived directly from the environment and the body.
- Dishabituation
- Dishabituation is renewed attention to a new stimulus after habituation, showing the infant discriminates old from new.
- Preference Technique
- The preference technique presents two stimuli and measures which one an infant attends to longer.
Infant Senses and Perception Research Methods FAQ
Which sense is least developed at birth?
Vision is the least mature sense in newborns. Visual acuity is about 20/240 at birth, improves to about 20/40 by six months and reaches adult level by twelve months. Hearing, by contrast, already works in the last two months of pregnancy and is more developed than vision at birth.
What does dishabituation tell a researcher?
Dishabituation is renewed interest, such as longer looking, when a new stimulus replaces one the infant has habituated to. It shows that the infant perceives a difference between the old and new stimuli. It does not by itself show which stimulus the infant prefers.
What is the high-amplitude sucking method?
It is a technique for studying infant perception in which researchers examine discrimination and preference from changes in an infant's rate of sucking on a special pacifier. It suits very young infants and sound stimuli, such as comparing responses to the mother's voice and a stranger's voice.
Exam move
Make a five-row table of the senses with one fact and one number each, and test yourself until you can fill it blank. Then sketch a habituation curve with a rebound, label both halves, and write the one-sentence conclusion each half supports.
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