Symptoms of autism are usually noticed first by parents and other caregivers sometime during the child's first 3 years. Although autism is present at birth, signs of the disorder can be difficult to identify or diagnose during infancy. Parents often become concerned when their toddler does not like to be held, does not seem interested in playing certain games, such as peekaboo, and does not begin to talk. Sometimes, a child with autism will start to talk at the same time as other children the same age, then lose his or her language skills. Parents also may be confused about their child's hearing abilities. It often seems that a child with autism does not hear, yet at other times, he or she may appear to hear a distant background noise, such as the whistle of a train.