Discuss the evidence from research into the development of infants’ visual perception during the first year of life. At birth, the infant’s eye is physically immature, as is the nervous system. It is increasingly accepted that infants enter the world with some innate knowledge, which is then built on via experience. There is an interplay, as infants develop, between perception, behavior and cognition, although this process is not linear, but rather all are part of an integrated system.
This essay will examine the four stages of the visual nervous system, and look at studies which have served to increase our understanding of how infants perceive the world, and how this perception develops and matures over the first year of life. It will also focus on the methodology of these studies, The visual nervous system can be divided into four main parts: the retina the optic nerve the lateral accentuate nucleus the visual cortex. The image formed on the retina, by the lens, of a newborn has about the same clarity and color as would be formed in an adult’s eye.
The infant’s eye, however, is less good at accommodation (the ability to focus the eye on objects at different distances). This inefficiency of accommodation could be due to a lack of retinal sensitivity to fine detail, or may be caused by maturities in any of the other three parts of the visual nervous system (Dates & Slater, 2005). Barroom et al, 1982 (cited in Dates & Slater, 2005) studied the migration of cones within the eye as the retina continues to develop following birth.
Cones are the part of the eye which are sensitive to fine detail and color, while rods are more attuned to black and white light. Following birth no new rods or TOMATO cones are formed, however the fovea (central area of the retina) of an infant does not eave as high a concentration of cones as the adult fovea, meaning that the infant is less able to perceive detail. The period within which this migration of cones is most active appears to be 2-3 months after birth. It is at this point that acuity seems to make the largest improvement.
Discuss the Evidence from Research Into the Development of Infants’ Visual Perception During the First Year of Life. By silverfish maturation which occurs shortly after birth (Yugoslav and Lectures, 1967, cited in Dates & Slater, 2005). They studied myelin, a form of insulation for nerve cells which improves the speed at which electrical impulses travel. The optic nerve lacks amelioration at birth, meaning that the coded electrical impulses carrying data from the retina to the visual cortex move more slowly, and the information gets diffused.
In studies, Yugoslav and Lectures showed that the process of amelioration is complete by 3 months, and so the infants visual perception is more defined by this point. The next part of the visual system is the lateral accentuate nucleus (LAG). This is a complex structure, situated at the base of the brain. One of the functions of the LAG s to translate the differing amounts of light between the middle and edge of the retina. Once again, the immaturity of the visual perception system, and lack of amelioration means that there is a lack of clarity in the centre of the infant’s visual field (Dates & Slater, 2005).
Finally, the data received from a visual stimulus arrives at the visual cortex. This is a highly complex structure, the mechanics of which are not fully understood. Some of the cells situated here interpret signals for light and dark areas (both lines and boundaries between areas) – these are known as ‘simple’ cells. Other cells, known as ‘complex’ cells, are more sensitive to movement. Size and color are interpreted by ‘hyperbole’ cells, which take their data from wider receptive fields (Michael, 1978, in Dates & Slater, 2005).
According to evidence from Horton and Hadley-White (1984), the TOMATO organization of these different cells into complex structures continues until at least 6 months of age. Having looked at how the infant eye differs biologically from an adult eye, from birth and in the following twelve months, it is now time to look at how these differences impact on the infant’s visual perception, and how these differences might be assessed. This is usually done by observing behaviors to gather evidence of what babies can and cannot do when exposed to different visual stimuli.
Marker & Marker (1998) cited in Slater & Dates, 2005, investigated how the scanning patterns of infants change during the first months of life. They found two major differences between the scanning actions of infants and older people; firstly, before 2-3 months infants inspect far fewer parts of a visual image, and secondly infants end to concentrate their gaze around the edges of an object or image, rather than on any particular feature contained within the image. These scanning movements, known as saccade, were detected by reflecting an infrared light beam off the surface of the eye, and plotting their movements.
In the sass, Faint made a major breakthrough in understanding how and what reasoning was that if there were measurable and consistent differences in which visual stimulus babies preferred to look at, then the babies must be able to perceive differences between the stimuli. Using a method known as forced choice preferential cooking (Atkinson, 2000, cited in Dates& Slater, 2005), two stimuli were presented at the same time to an infant, and an observer noted the amount of time spent gazing at each stimulus.
This was done by tracking the direction of gaze, and by using corneal reflection (the reflection of the stimulus on the cornea of the infant). Using these methods, Faint discovered that infants prefer more complex stimuli as they get older, have a preference for symmetry from four months onwards, have a liking for curves rather than straight lines and angles, and prefer moving stimuli to stationary ones. It was also shown that infants have a preference for real, three- dimensional objects over photographs of the same objects. These preferences echo what infants encounter in the real world around them.
There are two different types of experimental evidence which can illustrate the visual process. The first type is the observation of natural learning as it occurs, and the second is learning in a controlled laboratory setting. Bushnell (2003), showed that infants have a strong preference to look at their mother’s face, rather than that of a stranger, after a separation of a few minutes. This preference was observed to occur tit as little as an hour’s attention to the mother’s face, but grew stronger with more exposure. This is known as a familiarity preference.
Infants also show evidence of novelty preference – studied using ‘habituation’, where a stimulus is presented until the infant tires of looking at it (ii, it is habituated), and then a second stimulus is introduced. An increase in looking at the second stimulus indicates that the infant is able to discriminate between the two stimuli. Studies have shown that infants are able to discriminate between shapes, colors and faces from an early age (Dates & Slater, 2005) Slater et al (1990) showed that, despite a deficit in visual acuity, the infant’s visual world is still highly organized.
They looked at size constancy – the ability to perceive an object as the same size, in spite of different presentation distances, which in turn change the size of the image cast on the retina. 2 day old infants were shown a single object (a small or large cube, which during habituation was shown at different distances from the eyes). When tested again, the infants looked more at a different- sized cube, rather than the same-sized one, displaying a novelty preference, even Hough the two cubes were TAMA)II presented at different distances to ensure the size of the retinal image was the same.
By showing this novelty preference, it demonstrates that size constancy, a highly organized framework, is present from birth. Findings that infants can imitate facial gestures only minutes after birth (Residuals, 1988, in Dates & Slater, 2005). This was apparently first reported by one Piglet’s students, Olga Marmots, who discovered that if she stuck her tongue out at an infant, the baby responded in kind (which should not appear until the second year, according to Piglet’s theories).
This indicates that babies have an innate knowledge of their own face, which they can use to match a facial expression. In conclusion, it has been demonstrated that the visual perception of an infant, and the ability to perceive shape, color, form and structure, is not as developed as an adult’s at birth. However, there is a process of rapid development over the first 12 months of life, and many underlying preferences are present from very early on. In some studies, such as the size constancy or the mother/stranger discrimination tests, infants show remarkable visual competence.
Other areas, such as visual acuity rely on biological maturation processes, and continue to develop in the initial days and months after birth. The studies showing the ability to imitate some facial gestures from birth, would appear to indicate an innate programming for discrimination and bonding. References: Dates, J. And Slater, A. (2005) ‘Sensation and Perception’, in Dates, J. , Wood, C. And Grayson, A. (deeds) Psychological Development and Early Childhood, Oxford, Blackwell/ The Open University. (1 574 words)