Intellectual disability involves problems with general mental abilities that affect functioning in two areas:

• Intellectual functioning such as learning, problem-solving, judgement
• Adaptive functioning such as activities of daily life, communication and independent living

A full-scale IQ test score of around 70 to 75 indicates a significant limitation in intellectual functioning, interpreted in the context of the person's difficulties in general mental abilities.

Three areas of adaptive functioning:

• Conceptual – language, reading, writing, math, reasoning, knowledge, memory
• Social – empathy, social judgment, communication skills, the ability to follow the rules, the ability to maintain relationships
• Practical – self-sufficiency in areas such as personal care, job responsibilities, money management, recreation, organizing tasks

Assessment of adaptive functioning through standardized measures with the individual and interviews with the family members, teachers and caregivers, is highly effective.