Which of the following research findings showed that babies learn and recognize the familiar scent of their mother within just a few days of birth?

a. Babies would demonstrate a preference for a gauze pad that had been placed inside the bra of their mother over one that had been placed inside the bra of another nursing woman.
b. Babies preferred the scent of clothing that had been washed in the same detergent as their mother's clothes over clothing that had been washed in scent-free detergent.
c. Babies cried more when their diaper was changed by a nurse than when it was changed by their own mother.
d. Babies slept more soundly on a pillow that had been used by their mother the previous night over a pillow that had a fresh, unused pillowcase on it.

Answer: A