Hi - This is the OP - I just saw that this thread had been revived. Just to provide an update - my son is now 3 1/2 years old (he was 20 months when I originally wrote). As of 3 weeks ago - he has stopped head banging and fingers crossed that he won't start again.
When we was around 2 years old, I took him to two different pediatric neurologists primarily because I wanted to make sure that he wasn't permanently hurting himself by banging his head repeatedly for long periods of time. One of them told us that 10-15% of otherwise "normal" children will head bang - usually boys - for self soothing purposes - similar to twirling hair or sucking a thumb.
We took his pacifier away 3 weeks ago - I had delayed doing so because I feared his banging would become worse if it didn't have the stimulation of the sucking of the pacifier. Much to our shock - he actually stopped banging and has told us he no longer bangs because he doesn't have his pacifier.
We'll see - my hope is that he really has stopped for good. Time will tell

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