IQ Scores & Ratings
What is a good IQ score? What is a high IQ
score? What is a low IQ score? These are common questions,
particularly after someone finds out their score from an IQ test.
Terman (1916) developed the original notion of IQ and proposed this scale for
classifying IQ scores:
Over 140 - Genius or near genius
120 - 140 - Very superior intelligence
110 - 119 - Superior intelligence
90 - 109 - Normal or average intelligence
80 - 89 - Dullness
70 - 79 - Borderline deficiency
Under 70 - Definite feeble-mindedness
Normal Distribution & IQ Scores
The properties of the normal
distribution apply to IQ scores:
50% of IQ scores fall between 90 and 110
70% of IQ scores fall between 85 and 115
95% of IQ scores fall between 70 and 130
99.5% of IQ scores fall between 60 and 140
Low IQ & Mental Retardation
5% of people have an IQ under 70 and this is
generally considered as the benchmark for "mental retardation", a
condition of limited mental ability in that it produces difficulty in
adapting to the demands of life.
Severity of mental retardation can be broken
into 4 levels:
50-70 - Mild mental retardation (85%)
35-50 - Moderate mental retardation (10%)
20-35 - Severe mental retardation (4%)
IQ < 20 - Profound mental retardation (1%)
High IQ & Genius IQ
Genius IQ is generally considered to begin around 140 to 145,
representing ~.25% of the population (1 in 400). Here's a rough
- 115-124 - Above average (e.g., university students)
- 125-134 - Gifted (e.g., post-graduate students)
- 135-144 - Highly gifted (e.g., intellectuals)
- 145-154 - Genius (e.g., professors)
- 155-164 - Genius (e.g., Nobel Prize winners)
- 165-179 - High genius
- 180-200 - Highest genius
- >200 - "Unmeasurable genius"
More notes on High IQ and Genius IQ:
Einstein was considered to "only" have an IQ
of about 160.
Mensa is a society for people with high IQ, in the top
2% (1 in 50).
In 1926, psychologist Catherine Morris Cox
published a study "of the most eminent men and women" who had lived
between 1450 and 1850 to estimate what their IQs might have been.
to Estimated IQs
of the Greatest Geniuses.