picking fluff

A fairly frequently observed behaviour is where the severely mentally handicapped child picks fluff from a person's clothes (or bits from his hair) and puts these in his mouth.

One view of this could be as an expression of affection, of a desire to incorporate and possess the love object into the child, and keep the other person with the child permanently. This would be consistent with a strongly oral receptive/aggressive type of psychosexual developmental stage. It reminds us of the expression:-
" I could eat him/her up!"
It also has similarities with these phenomena:-
a. cannibalism, whether seen nowadays, in the west, or in the past in places like Papua New Guinea. Here the above mentioned very primitive level of thinking is probably involved, wherein the consumer imagines he will take in, and preserve, the object eaten, inside himself.
b. eating certain animals. A somewhat similar idea is the superstitious belief that eating something with some pronounced quality will give the consumer that quality, e.g. eating the heart of a lion, will give a warrior the qualities of bravery, ferocity and strength.
c. the grooming and bonding behaviour seen in chimpanzees.

Another quite common behaviour is that where the child chews or mouths his clothes, e.g. the neck or sleeves of her top, jumper etc., or her hair. Alternatively the child may grasp and tug these objects with her hands. As we know these objects are symbols of the parents, especially the mother, and these behaviours are therefore disguised attitudes towards these people. If the behaviour with the object involves the mouth the behaviour is, by definition, oral, and depending upon the tenor of the behaviour, either oral-aggressive, (biting and chewing) or oral receptive, (mouthing and sucking). These remarks also apply to the famous 'comfort cloths' of some children, often remnants of blankets etc.

I had just finished giving an English lesson to a 5 year old Thai boy. He'd come with his mother to my house. I observed that while sitting on the floor just behind his mother he began to pick bits off the back of her top and bring them to his mouth!
This is a normal boy of at least average IQ