TJ Pitchford For Soothing. "I'm OK". Think of baby pacifiers.
  They suck on the pacifier because mom takes the thumb out of the
  mouth (thumb was first) and it frees up the hand for other
  things. Then its bottles. Then juiceboxes. Somewhere late in
  juicebox time, moving towards Sunny-D/Monster time, getting
  friends becomes really important (like age 7-8 and beyond) - and
  at that point, "Good jo...b" and "attaboy" and "Like" and
  "You're cute/hot/awesome/sexy/amazing/beautiful/pretty/manly" or
  even "you're smart/you're talented" "I rate you a 10" - replaces
  the pacifier/bottle/juicebox for a source of comfort and a way
  of feelling "I'm ok". "