in her lab petitto and her graduate students work with a special machine petitto helped design. it's called the f nerves, a faster, quieter, and more portable version of an mri machine. if petitto was going to study the brains of infants she needed a way to look at them. >> this is quite an extraordinary new microscope into the brain. it also allows the baby to engage in more naturalistic behaviors. they can look, they can turn their head, they can move their hands. and this was very exciting. >> reporter: remember that baby babbling in sign language? well, petitto found that babies exposed to sign language hit the same developmental milestones as babies exposed to speech. for example, the first word and first sign both come around 12 months. that meant something was happening in the brain, unique to language.