brain scanner, the study monitors 7 to 11 and 12-month-old babies listening to sill be si syllables such as da and ta. researchers noticed an activation in the part of the brain that coordinate speech production. hello. how are you? that s the kind of speech that we think allows babies to mirror what they ought to do. reporter: so in the interest of brain development. hi. reporter: i make sure my little guy gets an earful of parentese daily. hi, my precious. reporter: besides, who could resist? linzie davis, abc news, new york. oh, baby is so cute. so true how they tell you say don t talk down to your baby. and they absorb language. especially around 2 years old. there s a fine line between baby talk and babble. you don t want to dumb it down too much. absolutely right. it s true. coming up, the world s largest yo-yo, so big it needs to be hung from a crane. and why mcdonald s has become a hot spot for some brides and grooms. that s ahead in the mix.