Why do mentally handicapped people "Bob"?

Question

Why do they nod back and forth? I can't seem to google up an answer.

Answer 1

Some nod (bob) back and forth due to self-stimulation (stimming).  

Answer 2

Sometimes it's a lack of muscle control.

It really just depends on the illness.

Some people are so severely handicapped, that they can only function as babies. Because of that, those people just do what feels good to them, without realizing that what they are doing looks strange.

It's a real shame. I wish a cure could be formulated for such illnesses.

Nobody deserves to be born into such a helpless existence.

Answer 3

Sometimes it is due to a neurological impairment and other times it has to do with a sensory integration issue.  Cognitive impairments may be developmental or secondary due to a neurological disorder.

Answer 4

not all mentally challenged people display the same mannerism.but sometimes the persistent nod back and forth is some sort of a stimulatory behavior to help them relax or help them regulate their environment.