The definition and classification of mental retardation

Area of Science:

• Psychology
• Psychometrics
• Developmental Disabilities

Background:

• Current definitions of mental retardation are problematic.
• Classification systems based on behavioral capabilities are criticized due to noncognitive performance determinants.

Purpose of the Study:

• To propose a revised definition of mental retardation based solely on IQ scores.
• To address limitations in assessing intellectual functioning and social adaptation.

Main Methods:

• Critique of existing classification systems for intellectual disability.
• Proposal for a definition based on IQ scores at least 2 standard deviations below the population mean.
• Consideration of etiological categories (organic, familial, undifferentiated).

Main Results:

• Behavioral capabilities are influenced by numerous noncognitive factors, complicating performance assessment.
• IQ scores are proposed as the most reliable current measure for defining intellectual disability.
• Etiology is identified as a significant predictor for group differences in classification.

Conclusions:

• Social adaptation and expected performance are considered correlates, not defining features, due to measurement unreliability.
• Labeling individuals with intellectual disability can be beneficial if it facilitates access to services and interventions.