The author is Mark Johnson, University of London.
Source: Introduction to Psychology book. Authors — R.L. Atkinson, R.S. Atkinson, E.E. Smith, D.J. Boehm, S. Nolen-Hoeksema. Under the general editorship of V.P. Zinchenko. 15th international edition, St. Petersburg, Prime Eurosign, 2007.
Many developmental psychologists now agree that both heredity and nurture are necessary for the normal development of perception. However, there is still much disagreement about the degree of importance of the influence of nature and nurture. Opinions on this issue are more than just philosophical reflections; they affect all kinds of experiments that have already been done. In this essay, I will argue that classifying certain aspects of perceptual development as either innate or acquired is too passive an approach that argues that either genes or environment determine the structure of the developing brain. On the contrary, I suggest that the development of perception is better characterized as an activity-dependent process involving complex and subtle interactions on many levels.
To illustrate my point, let’s look at a recent neurobiological study of the prenatal development of the visual cortex in rodents. The neurons studied in these experiments are involved in binocular vision. Experiments show that these neurons are prenatally tuned by their responses to internal waves of electrical activity elicited by information entering the visual cortex from the lateral geniculate body and the eye (Katz & Shatz, 1996). In other words, the response patterns of these visual cortex neurons are shaped by a kind of «virtual environment» generated by brain and eye cells. Although we can use the concept of «innate» more broadly to explain this example of development, we can also describe this process as the «learning» of cortical cells under the influence of information from their «brothers» in the lateral geniculate body and the eye. After birth, these same cortical neurons remain tuned in the same way, except that now the information coming to them reflects the structure of the world around them. Thus, when we examine development in detail, it becomes increasingly difficult to prove, as some theorists do (Spelke, 1998), that «innate knowledge» is fundamentally different from learning.
One can demonstrate the role of activity-dependent processes in the development of perception with another example — the ability to detect and recognize faces. Since it became known that there were areas of the cerebral cortex specialized in processing information about faces, many argued that this ability was innate. However, experiments with infants show that things are somewhat more complicated (Johnson, 1997). The tendency of newborns to pay more attention to faces appears to be based on a very primitive reflex system, which is set in motion by such a simple stimulus as three contrasting spots arranged like eyes and mouth. This explains why, during the first weeks of life, newborns look much more at faces than at other objects. It follows from this that the visual recognition circuits in the cortex receive more information related to faces and are thus formed under the influence of visual stimuli of this type. Now we can study this process using new methods of brain scanning. Similar studies have shown that the processing of facial images in the cerebral cortex of infants is less localized and less specialized than in adults. Only towards the end of their first year of life do infants discover adult patterns of brain specialization in processing information about faces, by which time they have already observed human faces in general for about 1000 hours.
Another example comes from studies of infant eye movements when tracking visible objects. Newborns have only a few primitive reflex eye movements, and it is not until the end of their first year of life that they can make most of the complex and precise kinds of jerky eye movements that adults do. Some argue that the limited abilities of newborns are sufficient to allow them to use and develop new brain circuits for the more sophisticated integration of visual and motor information required for adult eye movements, which they do. By 4 months, the baby already manages to make more than 3 million eye movements. In this way, the infant actively contributes to his own subsequent development. These considerations lead us to be skeptical of many claims of innate perceptual abilities based on experiments with infants 4 months of age and older. In fact, it has often been found that when the same experiments were carried out with young children, very different results were obtained, indicating fundamental changes in perceptual abilities during the first few weeks and months after birth (Haith, 1998).
It can be concluded that the perception of infants is not formed passively under the influence of genes or environment. Rather, its development is an activity-dependent process in which the infant plays the most active role during the first months of life, gaining experience necessary for subsequent development.