Explain the psychological importance of understanding one's development as an infant, child, or adolescent.
I do not necessarily think it is imperative that a parent fully understands the how's and why's of child-development, as long as the parent is willing to pick a path of parenting and attempt to stick with it, or, through trial-and error, discover what works for the family and the child. In the end, children do not necessarily know what is best for them. As long as they feel emotionally and physically secure, at the end of the day (or life) most agree that whether a child is raised by psychologically educated parents or not, he or she can certainly be healthy and successful one day.
As far as understanding child development, it is helpful (especially for parents) in embracing the unknown and building confidence when certain parenting techniques do not necessarily have immediate effects. Obviously understanding child development is necessary in the educational world, for building age-appropriate lessons and attempting to reach a large number of children at once. But for parents who are mostly one-on-one with their own children, I think knowledge of child development can be helpful, but certainly isn't necessary.
The other side of this is "understanding one's development," as in a grown person understanding their previous growth and development. Any time we gain knowledge into our past experience, light is shed upon our present actions, motivations and attitudes. Since this is so, "understanding one's development" has significant psychological importance so that one might feel more comfortable with one's experience in life and so that one might make the most and best of oneself.
I have always been fond of the quotation, "The child is father of the man" (Wordsworth). While the nature versus nurture battle, a false dichotomy if there ever was one, rages on, whatever each of us brings to life genetically, we are profoundly affected by the experiences, people, and feelings in our "worlds." I will concede that our memories of our early environment are to some degree constructed memories and that these are formed and overlaid by genetic tendencies, for example, shyness or optimism. However, to the degree one can remember and understand one's developmental years, one has the basis to change, to accept oneself, to navigate through the world in a better way.
As akannon discusses, the theories of Freud and Jung are powerful aids to an understanding of one's developing years and how these affect one's adult makeup and actions. We internalize our early experiences, and if they are damaging experiences, it is often through insight into how they were developmentally inappropriate that we grow.
Sometimes we find that Maslow's hierarchy of needs explains our adult needs and behaviors. What needs were met in our childhoods? What needs were not met in our childhoods? Without an understanding of this, it is difficult to address our own concerns, much less move beyond them to be fuller participants in our adult world.
As someone who often teaches adult learners, I have found that that Vygotsky's and Dewey's theories are powerful and helpful to some of my students. They learn that they are unable to move on sometimes because their previous learning, or lack thereof, was not scaffolded learning, whether that was in mathematics or in the soft skills one needs on the job. They start to understand that their learning deficits exist because their parents and early teachers did not provide an environment in which they could construct their own learning. Learning about these theories helps them to overcome these deficits.
All of these psychology greats and many more give us the tools to look back and recreate ourselves, to strive for self-actualization. An understanding of one's early years through the lens of psychology allows one to see one's childhood as one's childhood, not as a life sentence.
Sobering news for any parents out there: how you parent your child and the situation in which they are brought up in will have profound consequences for the rest of their life! Help! More seriously, however, many psychologists argue about the importance of the early years of every individual and how they are the most formative. Some psychologists actually go as far as to say that by the age of 10 (or it might be sooner) the blueprint of the individual has been laid and cannot be altered. All this serves to show how important those early years are.
I think that it is extremely important to understand the psychological development of an individual. I think that one does not go far in the field of psychology without examining the experiences of infancy, childhood, and adolescence in gaining greater insight to the psychological makeup of an individual. The field of psychology is driven by the idea that the individual experiences of youth play a profound impact on the people we are as adults. Freud's theories of both repression and sexuality, for example, are rooted in the experiences that help to result in psychological developments. Carl Jung, another preeminent psychologist, was very concerned with how individuals experiences help to form identity. An entire branch of psychology, developmental psychology, devotes itself to understand how experiences as infant, child, and adolescent impact both our identity and conception of self. I think that the importance of our past experiences cannot be undersold. This becomes the reason why parenting is so important, as it helps to establish the backbone of these experiences and, good or bad, help to create the identities of who we are as adults.
Oh my Gosh, this is amazing... never heard those theories before.