A recent study has one more benefit to add to the list: the chance to practice making new sounds, such as consonants like d and k, says psychologist Mary Fagan, coauthor of the study and a postdoctoral researcher at the Indiana University School of Medicine in Indianapolis. Because consonants are made by pressing lips together or touching the tongue to the top of the mouth, gnawing on a safe object automatically gives the baby's tongue the shape changes it needs to create certain sounds.
But that's not to say that anything should go in a child's mouth. Keep all small objects, like buttons and pennies, out of reach: Anything that can fit through a toilet-paper tube is too small. You'll also want to double-check that none of your baby's favorite chompers have been recalled for lead paint or other safety issues (visit cpsc.gov for a list). Some good bets for safe and satisfying mouthing include plastic keys, stacking rings, rattles, and good old fingers and hands.Lisa Guernsey is the author of Into the Minds of Babes: How Screen Time Affects Children From Birth to Age 5.