When LO was a baby, she found her thumb and used it to self-soothe to sleep. Without fail, she would suck her thumb for a few seconds and then conk out to sleep. When she's upset/scared she sucks her thumb to calm her down. All of this was fine by me. Now, at 14 months of age, LO walks around the house playing and toddling around but is now starting to constantly suck her thumb. When I try to take it out, she pops it back in.