Lecture 5: Perceptual development Flashcards
Sensation
the processing of basic information from the external world by sensory receptors in the sense organs and the brain. Sensory input is often ambiguous or incomplete.
Perception
organising and interpreting sensory information about the objects, events, and spatial layout of our surrounding world. Perception organises sensory input into representations that the brain can use.
Perception research in infants
Measured how long infants look at stimuli.
Fantz used this to demo that infants had visual preferences.
what did newborn perception research reveal
infants could discriminate between stimuli using the preferential looking and habituation techniques
Preferential-looking
involves showing infants two patterns or objects at a time to see if the infants have a preferences for one over the other.
habituation
involves repeatedly presenting an infant with a given stimulus until the response declines. If the infants response increases when a novel stimulus is presented, the researcher infers that the baby can discriminate between the old and new stimuli
Operant conditioning
for example, rewarding the infant with a particular sound (or taste, or smell) according to their sucking pattern. Measure which pattern the child responds with to ascertain which reward is preferred. can be used in prenatal listening.
William James
“The baby, assailèd by eyes, ears, nose, skin, and entrails at once, feels it all as one great blooming, buzzing confusion”
However is is not as chaotic as james predicted.
what can newborn children see
Visual acuity- sharpness of visual discrimination
How does visual acuity develop
The sharpness of infants’ visual discrimination develops so rapidly that it approaches that of adults by age 8 months and reaches full adult acuity by 6 years of age
How can visual acuity be estimated
An infant’s visual acuity can be estimated by comparing how long the baby looks at a striped pattern such as this one versus a plain grey square of the same size and overall brightness
Contrast sensitivity
Very young infants (up to 2 months) prefer to look at patterns of high visual contrast because they have poor contrast sensitivity (the ability to detect differences in light and dark areas)
This is because the cones (light-receptors) of the eye, which are concentrated in the fovea (the central region of the retina), differ from adults’ in size, shape, and spacing
Childrens eyes
Immaturity of children’s cone cells - not very well developed
Light sensitive neurons concentrated in the fovea in the retina
Different size and shape and further apart than in adults
Newborns have about 20/120 vision
develops rapidly from then
Implications for colour vision
Colour vision
Very young infants have limited colour vision, although by 2-3 months of age their colour vision is similar to that of adults’ (Kellman & Arterberry, 2006)
Infants can discriminate between two bright, vivid colours (high contrast) better than between two faint, pastel colours (low contrast)- due to cone cells
Scanning
Scanning One-month-olds (a) scan the perimeters of shapes, while two-month-olds (b) scan both the perimeters and the interiors of shapes (Maurer & Salapatek, 1976)- eyes move around something stationary. Begins at perimeter then develops to interior
Tracking
Tracking Although infants begin scanning the environment right away, they cannot track even slowly moving objects smoothly until 2 to 3 months of age (Aslin, 1981)
Smooth tracking movements
Faces
From birth, infants are drawn to faces because of a general bias toward configurations with more elements in the upper half than in the lower half
Newborns look longer at the left-hand images than the right-hand images (Simion et al., 2002)
From paying attention to real faces, the infant comes to recognize and prefer his or her own mother’s face after about only 12 cumulative hours of exposure (Bushnell, 1998)-
Developing face expertise- Pascalis et al (2002)
Adult humans able to tell the two (unfamiliar) men apart quite easily , but may still not be sure whether the two monkey photos are of different individuals or not
Pascalis et al. (2002) – adults and 9-month-old children have difficulty distinguishing monkey faces
But 6-month-olds just as good at distinguishing monkey faces as human faces-
Expertise helps us tell human faces apart.
Developing face expertise (Quinn et al., 2002)
From birth onward, infants look longer at faces that adults find more attractive than those adults rate as less attractive
Prefer female faces by around 3 months of age, unless primary caregiver is male (Quinn et al., 2002)
With experience, infants not only develop a preference for the type of face they see most often, but also come to understand the significance of different facial expressions – ~4-5 months
Pattern perception
Two-month-old infants can analyse and integrate separate elements of a visual display into a coherent pattern
Subjective contour.
Illusory square.
Kaniza arrangement
Only infants familiarised to the Kaniza arrangement in the top left show a significant preference away from squares (Ghim, 1990).
Hence, they must perceive a subjective square.
May not be present in newborns. Acuity?
Perceptual constancy
The perception of objects as being of constant size, shape, colour, etc., in spite of physical differences in the retinal image of the object
If an infant looks at the larger, but further away cube, researchers will conclude the child has size constancy (Slater et al., 1990) - they understand that it is twice as big but twice as far away.
Supporting the nativist position, visual experience does not seem to be necessary for perceptual constancy
Object segregration and movement
Infants who see the display in figure (a) perceive it as two separate objects, a rod moving behind a block
After habituating to the display, they look longer at two rod segments than at a single rod (b), indicating that they find the single rod familiar but the two segments novel
If they first see a display with no movement, they look equally long at the two test displays
This result reveals the importance of movement for object segregation (Kellman & Spelke, 1983)
Object segregation and gravity
young infants use common movement to perceive object segregation
Older infants, like adults, can use additional sources of information for object segregation, including their general knowledge about the world