I work with lots of people who have had head injuries. It is very common for people with head injuries to have poor impulse control and odd behaviors such as you describe. It usually has to do with damage to the frontal lobe of the brain, which is the part of the brain right behind your forehead. The frontal lobe is involved with emotions, impulse control, and regulating social behavior among other things. When damage occurs to that area you often see odd behaviors, strange habits, quirky personalities, etc as a results.
Depending on the severity of the brain injury sometimes behavioral interventions can be effective in changing those behaviors. Often a reward system will be beneficial if the person has some type of reward they want to work for. Every time they feel a desire to engage in the behavior if they do something else they get points or credits toward the reward. The reward really has to be something the person wants and that is different for everyone. Could be monetary, could be going to a movie, buying something special, etc.
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