This is often considered a highly impersonal and therefore largely imprecise and impractical framework for viewing development, especially since the purported events which have supposedly shaped the brain through evolution can never be observed. A more popular type of theory is cognitive development. Jean Piaget is considered the founder of this school of thought; after noticing that responses from children of different ages were qualitatively different, he identified several distinct stages of cognitive development and saw cognition as the primary facet of development, affecting the other areas more than vice versa (Newman 2007).
There are, of course, some serious ethical considerations when engaging in experiments with human beings, especially children who are not able to provide informed consent. Most scientific experiments require as many variables as possible to be controlled, so that a singular aspect of a phenomenon can be observed. This is usually ethically impossible when dealing with human beings, but case studies of extreme cases and carefully designed series of experiments that observe certain things from various angles can both help to overcome these issues. One interesting example of a finding brought out simply by many observations over an extended period of time is the development of a child's sense of self. There is evidence that toddlers become aware of themselves in a rudimentary physical...
2004). This is related to the ability for abstract and symbolic thought, which also begins to develop during early childhood but is not fully formed until later (Newman 2007).
This suggests that children in the pre-operational stage of development, Piaget's more descriptive term for toddlerhood and early childhood, and the developmental patterns they exhibit might not be as egocentric as Piaget himself theorized (Papalia et al. 2004). This is only one of many adjustments or outright refutations of Piaget's theory that have been made since he began his work in he 1920s and 30s, but it is not surprising that these theories are undergoing modification -- that is the way of science. It is somewhat more surprising, and a testament to the rigor and veracity of his claims, that Piaget's theories have been as well accepted as they are, given their arrival during the height of behaviorism in the United States (Newman 2007).
References
Clifton, A. (1995) Psychological Theory: Erikson. Accessed 9 July 2009. http://www.haverford.edu/psych/ddavis/p109g/erikson.stages.html
Newman, B. (2007). Theories of Human Development. New York: Routledge.
Papalia, D.; Olds, S. & Feldman, R. (2004). Human Development, 9th ed. New York: McGraw Hill.
