Auditory, Olfactory, Gustatory, and Tactile Perception
Visual Perception
- Auditory
- less sensitive than adults; sensitivity improves with age; may be adult-like at 2 years of age; can localize sounds at birth and react to loudness and duration; crude pitch discrimination has been shown as early as 4 days old (definite seen around third month).
- Olfactory and Gustatory
- difficult to discern between the development of the two because they are so closely related; newborns appear to react to certain odors, but may be caused more by pain than by smell; newborns prefer sweet tastes to sour or bitter ones; smell and taste are active during infancy but develop due to personal experiences.
- Tactile
- evidence that infants react reflexively to touch (search reflex, palmar grasp); reaction to pain has been monitored through various measures of stress.
Visual Acuity, Accommodation, and Peripheral Vision
- At birth, all parts necessary for sight are present and almost completely formed.
- However, the fova is incompletely developed and the muscles are immature.
- This causes issues with fixation, focus, and coordination of eye movements.
- Blinking and tear forming apparatuses are poory developed at birth.
- Debatable whether or not newborns posses color vision.
- Visual acuity, accommodation, peripheral vision, binocularity, fixation, tracking, color vision and form perception develop rapidly during the early weeks and months following birth
Methods of Studying Infant Perception
- There are a number of techniques and methods that can be used to study infant perception.
- Researchers often use indirect and naturalistic observation.
- Some techniques have limitations:
- may be unreliable; observers may not agree on that the response occurred or to what degree
- difficult to quantify; rapid and diffuse movements of the child make accuracy difficult
- is the response due to the stimulus or a change from no stimulus to a stimulus?
- Important not to overgeneralize from the data or to rely on only one or two studies as conclusive
- Observational assessment techniques
- Habituation: Single stimulus is presented repeatedly to the infant until a measurable decline is observed
- Dishabituation:New stimulus is presented and any recovery in responsiveness is recorded
- Evoked potentials: electrical brain responses that may be related to a stimulus because of where they originated
- Visual acuity: degree of detail that can be seen in an object.
- normal acuity is achieved gradually as the cornea rounds our and the lens flattens
- newborn focal distance is 4"-10"; increases almost daily until adult levels at about 6-12 months old.
- Accommodation: ability of the lens of each eye to vary its curvature to bring the retinal image into sharp focus.
- Haynes: adult-like accommodation doesn't occur until around month 4
- Banks: partial accommodation at 1 month; near adult-like focusing at 2 months
- Peripheral vision: visual field that can be seen without a change in fixation of the eyes. (adults are 90 degrees from the center of the eye)
- Tronick: visual field at 2 weeks is only 15 degrees but increases 40 degrees by 5th month
- Aslin and Salapatek:1-2 months 30 degrees
- Cohen: 6 months both central and peripheral systems are very mature
Form Perception
Contrast Sensitivity
Color Perception
Depth Perception
- The ability to distinguish between shapes and to discriminate among a variety of patterns.
- Haith: placed in a darkened room, newborns would look for subtle shadows and edges; would also respond to horizontal lines
- Kessen: newborns responded only to vertical high-contrast edges
- Frantz: newborns are able to perceive form and prefer curved lines to straight
- Salapatek: 3 conclusions from abundance of research
- Before 2 months, visual attention captured by a single or limited number of features of a figure or pattern.
- Before 1 or 2 months, little evidence that arrangement or pattern plays any role in visual selection or memory.
- Before 1 or 2 months, there is little evidence that the line of sight is attracted by anything more than the greatest number or size.
- Vision used first by newborns in responding to various light intensities.
- Consensual Pupillary Reflex
- Hershenson: 2-4 day olds looked at medium-intensity light longer than dim or bright
- Peeples and Teller: 2 month-olds could discriminate between bars of light against a black background nearly as well as adults.
- Has been found that newborns tighten their eyelids when sleeping in a brightly lit room.
- Also, tend to be more active in dim than bright light.
- Many studies have been conducted; info before the '60s was confusing/conflicting
- Hershenson: infants respond to brightness of color prior to responding to hue.
- Kellman and Arterberry: 2-3 months have similar color vision to adults
- Unknown whether infants younger than 10 weeks can discriminate colors
- Unknown if perception of infants is identical to that of adults but evidence supports that it is
- Cohen and Cashon: color perception appears to go through developmental pattern where infants begin processing at the lowest level; later they integrate and process information at a higher level
- Involves the ability to judge the distance of an object from oneself.
- Static: making depth or distance judgements with regard to stationary objects.
- Experiments by Gibson and Walk with glass
- Development is in part a function of experience
- Sensorimotor feedback through early locomotor experience is sufficient to account for development between prelocomotor and locomotor infants
- Dynamic: requires one to make distance judgments about moving objects.
- Studies by Von Holfsten
- Newborns as young as 5 days may make purposeful reaching movements toward moving objects.
- Present in a more sophisticated form by the 4th month
- However, movements toward an object are crude and demonstrate poor integration between the visual and motor systems.
- Adult-like reaching does not appear until around the 6th month
Chapter 9: Infant Perception