Friday, May 20, 2016

Then or Never: Critical periods in humans

In many, if not all, animals and birds there is a critical period shortly after birth in which certain events must occur for normal growth and maturation.  An early writer in this area, Konrad Lorenz, observed ducklings immediately after hatching.  He discovered they would follow any object of approximately the "right" size as if it were their mother, IF the duckling was exposed to the object immediately after hatching.  By the next day the critical period was closed, and such attachment (which he called "imprinting") could no longer occur.  Some photos exist that show Dr. Lorenz waddling along, crouched down, with a line of ducklings toddling along after him.

Dogs and wolves have been shown to have the same pattern.  If wolves are not exposed to and handled by humans within the first few days after birth, they become untameable and feral.  In dogs the critical period for socialization is considerably longer, and may be as long as 12 weeks, with 8 weeks common in certain breeds of dog. (My doctoral dissertation is in this area).

In humans there is known at least one critical period for language development. If children are not talked to or cannot hear language in the first 3 or 4 years of life, they will never be able to learn to speak.  (I have not looked up this period and am not sure whether the length of time I have cited is accurate.)

It has occurred to me that there may be a critical period in humans and other primates for belonging to a group or pack.  We are group animals, of course.  We seek out groups to which to belong.  This process can be seen in children somewhere before puberty usually noticeable at age 10 and later.  It becomes more and more important through the teen years.  In this period groups form, whether gangs or social groups or interest groups.  What group you belong to is increasingly important.

Group boundaries can be marked by clothing or location or by title.  Probably other methods of marking boundaries can be found.  Transgressing a boundary can be a life-threatening event.  What people wear becomes extremely important, sometimes puzzling parents, but when this happens the clothing items are boundary markers, and not having the right item can mean exclusion and humiliation.

In non-human primates being excluded is a life or death issue, and we probably have some genes that dictate this level of importance to membership.  It is obvious that membership is highly valued;  young people have accepted "beat-downs" or group rapes as the price of belonging to a particular group.
Adolescents have committed suicide because of group exclusion or rejection.  College students may accept "hazing", sometimes quite severe, as the price of belonging to a fraternity or sorority.

So the importance of belonging is clear.  We all experience it to a degree.  Even adults frequently find group membership highly important.  What is less clear is what happens to people who don't achieve group membership during what may be a critical period for group membership.

These people are seen by other adolescents as "weirdos", "geeks", "loners" and other pejorative names.  It appears to me that school shootings have been carried out entirely by loners, non-members of groups, who are filled with otherwise inexplicable rage at those who "belong".  Adults who were not accepted in groups during their adolescence are not comfortable with adult groups. They rarely join clubs.  In many ways they (we) don't seem to quite know how to belong.  They don't get the cues, wear the right clothes, have the right behavioral signals (i.e. "manners").  The tend to be loners their entire lives.  Even when they marry, their families tend to remain socially isolate.

This is particularly observable in military families, in which the teen=age children are moved several times during the critical period for belonging, i.e. the high school years.  As adults they tend to stay on the outside of groups and are isolated to a degree even in their neighborhoods.  They tend to think of themselves as "different", "un-social", and equivalent titles.  In my opinion they will never be able to overcome their sense of isolation.  In a funny sense, they (we) are feral as far as groups are concerned.

Human infants learn at a very early age (prior to 1) to mimic expressions on a parental face.  This "mirroring reflex" is automatic and apparently not accompanied by a specific matching feeling.  For instance, when the parent face is smiling, the infant "smiles";  when the parent frowns, so does the infant, but does not apparently feel badly.  Just the expression itself is mimicked.  Very specific neurons in the human brain (and in some primates) are involved.  I wonder if the beginnings of social isolation are found in a failure of the parent to provide such up-close and personal contact at a critical period as yet unidentified.

Certainly some of us on the autistic spectrum have difficulty recognizing and responding appropriately to facial expressions, tones of voice, body language and the like.  This makes us easily identifiable as potential social isolates.  Asperger's syndrome is an example.  However, intellectual understanding of social cues can help supplement or replace missing instinctual responses.  We can learn what a specific expression means and practice appropriate responses, which can conceal the genuine social awkwardness that underlies it.

It puzzles me that there has been so little research in this general area, which is obviously of considerable importance to understanding normal and aberrant human development.