How does the nature and quality of parenting that a child experiences early in life affect how she functions later in life? That is a central issue when trying to understanding the role of early experience in psychological and behavioral development. As it turns out, investigating the topic of whether experiences had early in life exert an enduring influence on how a child functions later in life is not just fundamentally important and interesting but rather challenging.
In an ideal world, at least an ideal scientific--even if ethically horrible--one, the task would be rather straightfoward: Simply decide, on a random basis, that some children will be parented, for instance, in a warm, sensitive, emotionally supportive and intellectually stimulating manner and that others will be cared for in just the opposite way. Then follow the children up at a later age and make comparisons between them. Any differences would be attributable to effects of early rearing.
For this research to yield truly compelling answers to questions about enduring influences of parenting early in life on development later in life, the skilled scientist would not even rely on biological parents to rear their own children--in the manner the scientist dictates--but have other, unrelated adults do the job. This kind of investigatory freedom is engaged in all the time when animals are the focus of investigation. Some such work, for example, takes rats or monkeys away from their biological mothers and hands them over to another adult (of the same species) who is known, on the basis of prior study of their parenting skills, to care for offspring very well or very poorly. An alternative strategy is to induce the adult who provides foster care to the young animal to care for their pseudo-progeny in a sensitive or insensitive manner by modifying the conditions under which parent and child live--by, for example, creating crowded or comfortable conditions, by providing sufficient food or doing the opposite, and so on and so forth. Once again, comparisons between animals cared for well or poorly early in life allow one to discern enduring effects of early care when the animals are studied later in life.
Because this kind of experimentation is not permitted on humans, scientists studying child development have two choices as to how to proceed. One is to seek out "natural experiments", though sometimes these seem anything but natural. Consider in this regard research on early experience effects focused upon the long-term development of children who had the misfortune of being dumped into terribly deprived Romanian orphanages when the Communists were in power and compared with children who either were not so "cared" for or simply spent less time in such places. By comparing those who had more and less exposure to these conditions of deprivation early in life, one can discern whether there are long term effects of such early experiences.
However elegant such studies can be, such research, like much early experience work involving animals, often leaves one wondering about the effects of mainstream family life--in which experimenters are not free to manipulate parenting practices and parenting experiences do not qualify as inhumane.
One way to proceed in this situation as a developmental scientist is to follow for many years children and families, studying carefully what goes on in their lives. If one wants to know how parenting in, say, the infant, toddler and preschool years might influence children when they are, say, 11 and 12, it is essential to do several things. The first is to take into account--that is, statistically control for--effects of family factors that might be related to parenting and even account for putative effects of parenting. A second important thing to do, if possible, is to take into account parenting experienced subsequent to the early years to insure that apparent effects of early parenting are not simply a function of later parenting which ends up being related to early parenting.
I have been heavily involved in one study that has followed this practice, with a sample of over 1300 Amereican children followed from birth to age 12. We discovered that the quality of parenting experienced across the first 4 ½ years of life consistently predicted many aspects of children's functioning even after we had taken into consideration a laundry list of alternative sources of influence, including family economic and educational resources early and later in the child's life, whether the mother was a single parent early and later in the child's life, mother's tendency to be depressed early and later in the child's life, the quality, quantity and type of child care the child experienced during the infant, toddler and preschool years, and the quality of instruction and the emotional support the child experienced at school in 1st, 3rd and 5th grade. Even with all these (and more) alternative sources of potential influence accounted for, many will not be surprised to learn what we found: When children experienced parenting that was warm, sensitive, cognitively stimulating and not intrusive or over controlling early in life, children showed better cognitive functioning, academic achievement and social adjustment when in 5th and 6th grade. The opposite was true when children experienced care that could not be characterized this way. (see: http://www3.interscience.wiley.com/journal/117957245/abstract)
Will these apparently beneficial effects of parenting in the early years extend into adolescence? That is a question we are presently addressing and should be reporting on in the not too distant future. Of interest perhaps is that these findings underscoring the enduring influence of parenting during the early years emerged from a major study whose core purpose was to investigate the effects of early (non-maternal) child care on child development, a subject that will have to wait for a future blog.