You know, I felt bad about the flippancy of my response so here is a resurrection. I don't have Attention Deficit Disorder but I do have an Obsessive/Compulsive bent. It is almost like I am trying to create one for myself.

For instance, especially when I am out walking if a syllable occurs to me, I have to see how many words can be made by adding a single letter in front.

If I happen to think of 'ard', I go down the list: bard, card, hard, lard, pard, ward...

Or 'ere': here, mere, sere, were...

And then I remind myself that 'w' usually changes the vowel sound from that of the others.

When I get tired of it, I am able to stop. However, I don't know why I do it in the first place.