Mental retardation lies at the bottom extreme of intelligence. It is currently termed as “mentally challenged”. Mental retardation refers to a sub-average level of intelligence which is manifested in about two or more areas of performance such as self-care, home living, social skills, learning safety and health, self-direction and work. About one to three percent of the population is found to be mentally retarded.
The current conceptualization of mental retardation is “the intelligence test performance two or more standard deviations below the mean having limitations in adaptive functioning such as failure to cope with the common tasks of daily living appropriate to one’s age and situation”. People categorized as mentally retarded can range from those who can be taught to work and do simple errands with little special attention to those who cannot dress themselves, and cannot be trained. The late- category must receive institutional treatment for their lifetime.
Mentally retarded with minor deficits are classified as mild retarded. The IQ scores range from 55 to 69 and they constitute 80 percent of total retarded population. They can take simple jobs involving gross manual labor. Other levels of retardation are termed as moderately retarded (IQs from 40 to 54) severely retarded (IQs from 25 to 39), and profoundly retarded (IQs below 25).
Below is given the table of classification of mental retardation along with their abilities of adaptation which includes capacity for self-care, speech and communication, learning, social interaction, vocational abilities and possibilities of marriage.