The main characteristics of mental retardation include a lower-than-average intelligent quotient (IQ), difficulty with practical daily life skills, learning difficulties or disabilities, developmental delays, memory problems and lower attention spans. Not every person who is diagnosed with mental retardation will display every common characteristic, but most of them are present to some extent in the majority of mentally retarded individuals. Mental retardation also can be linked with physical disabilities and an abnormal physical appearance.
There are four main classifications of mental retardation: mild, moderate, severe and profound. The characteristics are more pronounced in individuals who have severe and profound retardation. People who have been diagnosed with mild retardation make up the bulk of mental retardation diagnoses, however, and these individuals can often learn to function in society at a basic level despite their disadvantages.
IQ tests are an important part of a mental retardation diagnoses. Individuals who are mentally retarded have IQs that are at least two-thirds lower than the average IQ for their age groups. Their lower overall intelligence levels are why mentally retarded individuals struggle to learn in academic and social environments. As children, they often require special teachers or classrooms to help them learn. Teaching a mentally retarded child basic skills, such as personal hygiene, usually requires more time and repetition than it takes to teach a child of average intelligence the same skills.
Developmental delays are common characteristics of mental retardation and are present to some extent in all mentally retarded individuals. Mentally retarded children often do not speak until later in life, if they learn to communicate through speech at all. Physical delays also are common, particularly in regard to coordination, balance and dexterity. Children who are born with certain syndromes, such as Down syndrome or fetal alcohol syndrome, are particularly prone to delays in physical development.
Memory problems and short attention spans are other common signs of mental retardation. These signs typically manifest early in life for children who are born mentally retarded. People who undergo trauma that results in brain damage later in life also often display these characteristics. Mentally retarded individuals often find it difficult or even impossible to focus on a particular task or concept for more than a short period of time. Shorter attention spans often make memory problems more pronounced because individuals who cannot concentrate long enough to learn a task or concept have trouble recalling the information later.
Every patient's situation is unique in some way, so characteristics of mental retardation that are present in some people might be undetectable in others. For example, many mentally retarded individuals who are able to speak have difficulty with pronunciation and sentence structure, while many mildly retarded individuals can speak normally. Many mentally retarded individuals also suffer from related disorders and problems, such as seizures, attention-deficit hyperactivity disorder (ADHD), depression, autism and behavioral disorders.