Yes, that is the famous sucking of the thumb! He loves it! And there isn't much we can do about it when he is asleep. If you can see the time of my post, you will see that I wish I could suck my thumb and go back to sleep!
Since we are on the topic of sleep, I don't think I have ever appreciated my amazing ability to sleep at any time. This week I have been plagued with waking up at 3:00 and not going back to sleep. I have had the same concealer for 100 years and I think I've managed to use it up this week for the dark circles.