why do we smile?
The primary one bred in us (i.e. we're born with this one ...)
"..... as one headline said: "Baby's smile lights up mom's brain." Well, of course.
Researchers used MRI scans to confirm that certain parts of a mother's brain are activated by her baby's smile. Also not surprisingly, the study concluded that a crying baby did not produce the same response.
That natural stimulus is just one of the bountiful rewards a mother gets for enduring near-death pain and, er, fear. The study targeted first-time mothers, but I'm sure this second time around will prove the same effect.
... Published in the July (2008?) issue of Pediatrics, the journal of the American Academy of Pediatrics, the study confirms an intuitive, common-sense certainty: "When first-time mothers see their own infant's face, an extensive brain network seems to be activated ... " "