Children who fail to meet intellectual and physical milestones may have a developmental delay.
Developmental delay is an umbrella term used to encompass a variety of disorders in which children do not progress as expected in terms of cognitive, motor, social or language skills. Unlike children who simply lag behind their peers for a time, developmental delay is characterized by an ongoing delay, often noticed first by parents, according to the University of Michigan Health System. Developmental delay requires diagnosis by a doctor.
Impaired Social Interactions
Autism, one form of developmental delay, frequently draws a parent's notice because children have little to no interest in social interactions normal for children their age. While children with autism may rely on others to meet their needs, such as taking an adult's hand to lead them to the refrigerator for a snack, they show diminished interest in forming deeper relationships. In their book "Abnormal Psychology," psychologists David H. Barlow and Mark Durand describe how children with autism will sometimes sit on a parent's lap, as expected, but want to face away from the parent.
Infants arrive with the ability to process language, and in the first few years of life, children make enormous gains in language acquisition. Some developmental delays show up when a child fails to speak, cannot use or understand language according to his intellectual capacity or lags significantly behind peers. Language delays take a variety of forms and may co-occur with disorders such as autism or cognitive disability.
Similar to language development, children also tend to develop intellectual abilities in a predictable trajectory with milestones occurring at certain ages. For example, after about two years of age, children will remember the location of a toy after it's hidden, according to the book "Educational Psychology." Children whose school performance or intelligence tests scores are below expectations for their age may have a cognitive disability, also known as an intellectual disability or mental retardation. Children with cognitive disabilities frequently show other delays as well, such as language delays.
Difficulties With Body Control
Children reach milestones for motor control at different ages, and small differences are not a reason for concern. However, when small children progress far beyond a basic milestone--such as being able to hold up their heads unaided--or show other physical symptoms like floppy limbs, rigidity, frequent arching of the back or use of only one side or certain body parts, the child may have a developmental delay in motor skills. As with all suspected developmental delays, early identification is the key to providing treatment.
Dawn Walls-Thumma, eHow Contributor