Q.All persons do not have the same intellectual capacity. How do individuals vary in their intellectual ability? Explain.

People vary widely in intellectual ability, from intellectual deficiency at one extreme to giftedness at the other, with most in the average range (the normal curve). The intellectually disabled (IQ below 70) show significantly sub-average functioning plus deficits in adaptive behaviour arising during the developmental period (0–18 years), graded as mild, moderate, severe and profound. The intellectually gifted (IQ around 130 and above) show outstanding potential, high ability, high creativity and high commitment, with early signs of superiority. In between lie people of average and above/below-average intelli …

A continuum of ability

Not all persons have the same intellectual capacity. IQ scores are spread on a normal (bell-shaped) curve: most people cluster near the average (IQ 90–109), while only a few fall at the extremes of very high or very low ability. The two extremes deviate considerably from the normal population in their cognitive, emotional and motivational characteristics.

Intellectual deficiency (the disabled)

Children who face enormous difficulty learning even simple skills are termed intellectually disabled. The American Association on Mental Deficiency (AAMD) defines intellectual disability as significantly sub-average general intellectual functioning existing concurrently with deficits in adaptive behaviour and manifested during the developmental period. This gives three features:

• Significantly sub-average intellectual functioning — an IQ below 70.
• Deficits in adaptive behaviour — an inability to be independent and deal effectively with one's environment.
• Onset during the developmental period — between 0 and 18 years of age.

There is wide variation among the disabled, graded by severity:

• Mild (IQ ~55 to ~70) — slower development, but can function fairly independently and hold jobs.
• Moderate (IQ ~35–40 to ~50–55) — lag in language and motor skills; can be trained in self-care and simple communication with supervision.
• Severe (IQ ~20–25 to ~35–40) and Profound (IQ below ~20–25) — incapable of managing life and need constant care.

Intellectual giftedness …