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
Depth Perception
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
Stereopsis
Process by which the visual cortex combines the differing neural signals caused by binocular disparity (the slightly different signals sent to the brain by the two eyes)
Emerges suddenly at around 4 months of age (Held et al., 1980)
Depth perception
about 6–7 months of age, infants become sensitive to a variety of monocular or pictorial cues, the perceptual cues of depth that can be achieved by one eye alone
These include relative size (larger is closer), interposition (overlapping) and linear perspective (convergence of parallel lines)- meaning a single point of origin
7 month old infant and depth perception
This 7-month-old infant is using the monocular depth cue of relative size (Yonas et al., 1978)
Wearing an eye patch to take away binocular depth information, he is reaching to the longer side of a trapezoidal window - aims window.
This behaviour indicates that the baby sees it as the nearer, and hence more readily reachable, side of a regular window
Pictorial representations
Despite the fact that even newborns can recognize two dimensional versions of three dimensional objects, children must come to understand their symbolic nature
Before they reach about 19 months of age and have substantial experience with pictures, infants and toddlers attempt to treat pictures as though they were real objects (DeLoache et al, 1998)
How does hearing develop
Although the human auditory system is relatively well developed at birth, hearing does not approach adult levels until age 5 or 6
Auditory perception
Newborns turn toward sounds, a phenomenon referred to as auditory localization.
Wertheimer (1961) – 10 mins old
Clarkson & Clifton (1991) – Continuous sound is best.
Infants are remarkably proficient in perceiving subtle differences in human speech
Perception of speech sounds
At 2 months of age (Eimas, 1985):
Allow infant to suck on soother (dummy) that is connected to a computer and measure baseline sucking rate
Present phoneme (/pa/) repeatedly
Sucking rate first increases and then infant habituates (i.e., returns to baseline sucking rate)
Present new phoneme (/ba/)
Infant dishabituates (i.e., sucking rate increases)
Perception of music (biological)
Biological foundation
Butt and Kisilevsky (2000)
Heel lance procedure on premature infants 31 weeks GA
Heart rate returned to normal more quickly when played Brahms lullaby (regardless of instrument)
Not present for infants <31 weeks GA (gestational age)
Control condition?
Perception of music
Infants share the strong preferences adults have for some “pleasing” music sounds over others (Trainor & Heinmiller, 1998)
Infants respond to rhythm and temporal organisation in music, preferring music that had pauses between musical phrases rather than in the middle (Krumhansl & Jusczyk, 1990)
Infants are also sensitive to melody, showing habituation to the same tune (a particular sequence of notes) regardless of changes to the musical key (pitch) (Chang & Trehub, 1977)
Preference for sweetness shown at birth studies. Marlier
Marlier et al. (1998)
Newborn infants prefer the smell of their “own ‘’ amniotic fluid relative to that of another baby.
Teicher & Blass (1977)
taste and smell
Amniotic fluid promotes post-birth feeding behaviour in RATS
Baby rats navigate to mother rat for feeding very soon after birth
If mother rat is washed immediately after birth – pups don’t find food source
Marlier and Schall
Newborns prefer the smell of breast milk, their natural food source (Marlier & Schall, 2005)
Regardless of whether they have been breastfed or bottle fed (i.e., have never tasted breast milk)
Taste and smell in the newborn
By two weeks of age, babies appear to be able to differentiate the scent of their own mothers from that of other women, an ability shared by a variety of infant mammals (MacFarlane, 1975)
Touch and intermodal perception (video)
Very young infants link sight and sound, oral and visual experience, and visual and tactile experience how info from more than once sense is put together
When two videos are presented simultaneously, 4- month-old infants prefer to watch the images that correspond to the sounds they are hearing (Spelke, 1976, 1979) - will watch video that corresponds with sounds
Using a similar technique, researchers have found that by 5 months of age, infants associate facial expressions with emotion in voices (Walker-Andrews, 1997)
Intermodel perception (rings)
Infants held two rings, one in each hand, under a cloth that prevented them from seeing the rings or their own bodies
For some infants the rings were connected by a rigid bar and therefore moved together
For others the rings were connected by a flexible cord and therefore moved independently
All the infants were allowed to hold and feel just one or the other type of rings until they had largely lost interest (habituated).
They were then shown both types of rings and looked longer at the rings that were different from those they had been exploring with their hands (Streri & Spelke, 1988)
