8 ~ 9 is sub-normal ability.

? The boundary of normal intelligence is that IQ is 9-11, and IQ is 2 points. Those who score 9-11 belong to the normal intelligence range, those who score 12-14 are smart people, and those who score above 14 are called geniuses.

The lower the score, the worse the intelligence, and the IQ below 7 is a quantitative indicator of people's intelligence. It was put forward by German psychologist Steen in 1912. IQ is the abbreviation of intelligence quotient, and IQ is expressed in English. IQ is the quotient obtained by dividing the intellectual age by the physiological age.

The intellectual age can only indicate the absolute intelligence level, but not the intelligence level of children of different physiological ages. For example, A child is 5 years old physically and 6 years old intellectually, while B child is 1 years old and 11 years old intellectually. Both children are one year older than their physical age, so it is difficult to compare their intelligence.