Researchers explore infants' mental abilities through tests of habituation, where they measure infants' decreased interest in repeated stimuli over time. This allows researchers to determine what infants prefer to look at, like human faces over other images. Infant brain and motor development occurs rapidly during the first years of life. The brain grows dramatically as new neural connections are formed. Infants develop motor skills like grasping, stepping, and balance. Early experiences and maturation enable new cognitive and physical abilities during this critical period of development.