Severe Mental Retardation
An IQ score between 20-25 and 40.
Example: Behavioral observations of a twelve-year-old child indicate that his capacity for adaptive learning is at the average level for four-year-olds.
Her is a list of caegories that show general guidelines for judging the level of retardation including mild, moderate-severe, and severe: http://www.cloudnet.com/~edrbsass/mrcharacteristics.htm
Fournier, G. (2010). Severe Mental Retardation. Psych Central. Retrieved on February 13, 2016, from http://psychcentral.com/encyclopedia/severe-mental-retardation/