The term "intellectual disability" is a specific type of disability. It is caused by limited mental capacity. Limited mental capacity makes it difficult to develop important mental abilities. This includes reasoning, planning, thinking, and judgment. This limited mental capacity makes it difficult to learn new things. The ability to learn is a very important mental ability. We learn new information and skills in school. We learn from our past mistakes. We learn how to do many things by watching others. When this ability to learn is lacking, it causes many problems in everyday life.
The Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Association (APA, 2013) lists three main criteria for intellectual disabilities:
1. Significant limitations in intellectual functioning (mental abilities);
2. Significant limitations in adaptive functioning (conceptual skills, social skills, and practical life skills);