Sleeping Beauty?

My extremely brilliant boy has been sleeping superbly well! Three nights in a row of sleeping through the night, thank you sweet baby. However, during his nap yesterday he would randomly scream a scream that was not described in the Baby Whisperer, so I had no clue what it meant. Being the good mother I am, I responded, not rescued, and every time I peeked at him in his bed, he was sleeping. Continuing on with my chores, yes the dirt under the rug is gone, I would again hear the scream, and again he would be a sleep. I finally stayed in his room to observe what was going on. It seems my brilliant boy wraps his fingers around a chunk of his hair and pulls quite hard, screams, and lets go. Again, being the good mother I am, I took a picture of this. He did this three more times while I watched him before I wrapped up his arms. He's so smart...