Functioning is absolutely minimal… incapable of self-maintenance in any way. Can’t even be toilet-trained.
Between 12 and 28
Profound retardation. Once known as “idiots”, this group are without understanding or ordinary mental capacity. Need constant care and supervision. An IQ of 20 is the beginning of a semblance of humanity - cats are at this level.
28 to 44
Severely retarded. Once called “imbeciles”. Congenitally weak-minded, they cannot profit from academic training at all, cannot be employed in sheltered workshops and must be supervised domestically. Demonstrate little or no social and communication skills but they can be trained in basic health habits. Smart dogs are estimated to have IQs at this level.
Moderately retarded. Limited support is essential and with extended special education a maximum of Grade four could be attained by age 18. Their thinking does not involve much in the way of logic. Their ethical thinking has to involve conditioning, but there is the beginning of a quid pro quo sort of morality. Their social and communication skills are fair but there is little self-awareness. They can function vocationally in a sheltered workshop (and perhaps lawn-mowing, if you don’t mind them losing fingers). Cannot live independently. Average adult chimpanzee has a general intelligence level corresponding to this category.
60 to 76
(Mental age 12 for adults) Mildly retarded. Once called “morons” or “feeble-minded”. With special education, a maximum of grade six is possible by age 18. Are inevitably functionally illiterate even if they have been taught to read for at least four years. Real (if superficial and concrete) logic appears in this category.Conventional morality also begins to appear - this group perceive as good whatever pleases significant others and the bad as anything that displeases them. At least some intermittent outside assistance is necessary. Their communication and social skills are reasonable. (By social/communication this does not refer to negotiation skills or wit, but basics such as washing hands, dressing, brushing teeth, using toilet paper, looking at the person addressing them and finding the local doctor.) They are socially and vocationally adequate (at menial labour) given special training and supervision. Many are able to lead a relatively independent life. At an IQ of 70 or below the law regards them as being too stupid to know the difference between right and wrong.
Dull. Life is tough at this level. Learning is slow, simple and needs to be supervised closely to be effective. With application they may graduate from primary school but will flounder badly in high school. Those with IQs below 80 will probably never be functionally literate and the rest will not understand anything more complex than a popular magazine. Their reasoning is very superficial. Morality is of a primitive conventional sort - good and bad depends on how significant others view good and bad. The vast majority of serious social problems are associated with people in this category because there are so many of them and they are just smart enough to be let loose. People in this category commit about 75 percent of all petty and violent crimes. Anything other than unskilled labour is a trial, though simple semi-skilled work is possible.
92 to 108
Mediocre - the average person. Learning varies from explicit coaching with hands-on experience to study guides and textbook work with some practical experience. They should be able to deal with a high school curriculum and graduate, but even with hard work won’t do well enough to enter university. Their reading level is, at best, news stories (not editorials), popular magazines and novels. Morality is conventional - a matter of serving the social order and tradition or doing your duty as defined by some authority - church, teacher, parent or state. Able to function at the level of skilled blue-collar, clerical, sales or police work. This large group are the glue of society, but, given the wrong authority, they will do horrible things in the name of morality.
Bright. They can learn via the typical university format of lectures and textbooks. They would struggle at, but sometimes graduate from, university. Their best reading level is editorials, magazines such as Time and The Economist, and classical novels. Abstract, “what-if” hypothetical thinking begins in this group but is still superficial. Principled morality also begins in this group, that is, they can see there are non-arbitrary principles or laws that should govern ethical behaviour and thought. They can also see that these laws are social constructs and have not come down from heaven or any other ultimate authority. Their best work level is that of most teachers, low- to middle-level management and military officers, sub-standard to fair professionals and some elected national or provincial politicians. This group makes up the moral, intellectual and practical leadership assistants of society.
124 to 140
Superior. This category and all those above them don’t require assistance to learn. They can find the information and master the methods themselves. Capable of postgraduate work, including PhDs, but may struggle with a few subjects such as postgraduate mathematics, physics and philosophy. Reading philosophy and legal tracts with comprehension is possible. Morality is decidedly a matter of principles for this group but nevertheless they tend to accept established systems - rarely is the principled system a self-chosen one. This group forms the bulk of the better doctors, lawyers, engineers, accountants and other professionals, United States presidents, CEOs of large companies and academics. Tend to be the keepers, and transmitters of knowledge and the higher points of any culture, but can’t create it themselves.
Brilliant. Highly regarded original academic work rarely occurs with lower IQs. Some in this group exceed the average university student in academic competence while still in primary school. They garner most academic honours such as Rhodes scholarships and maths Olympiads. They can read anything and probably read philosophy for pleasure. Most professional mathematicians, physicists, philosophers and judges or very senior counsel can be found in this group. Many Nobel laureates and some historical geniuses - like Sartre - are also to be found here. People in this category make up society’s intellectual leaders. Most original ideas start with these people. However their contribution tends to be in bits and pieces rather than a whole new system or new way of seeing things. One in 1000 people reach an IQ of 148.
156 to 172
Genius. Most exceed the average postgraduate in academic competence - even professors - while still in primary school and probably knew more than their teachers from about grade four. They can and do read philosophy for pleasure well before puberty and can read at the university level before the average person can comprehend a primary reader (that is, “I see a cat”). The smarter Nobel Prize winners and most historical geniuses (people such as Einstein, Hawkins, Byron, Milton, Kant, Newton, Bertrand Russell, Ayn Rand) are to be found in this category. They are the source of virtually all of humanity’s advances. A common experience with people in this category or higher is that they are not wanted - the masses (including the professional classes) find them an affront of some sort. Fortunately, they are plentiful in absolute numbers - South Africa probably has about 1 500 - so many of them do rise above the envy and hostility.
Freakish. While still of primary school age, only around one in 1000 professors can look them in the eye intellectually. They tend to read competently before they are three years old. Keynes - who used to intimidate Russell - was probably in this category. Zietsman believes that FW Nietzsche, the German philosopher and poet, and Hugo de Groote, a jurist, were others. Michael Kerney, who holds the world record as the youngest university graduate ever at 10 years old, probably also has an adult IQ around 186 on this scale. Only one in a million people are this intelligent. They are seldom understood or appreciated. Most feel profoundly isolated from society - even when they are appreciated. A large proportion of this group opt out of society and never make revolutionary contributions in the standard academic fields or professions. It seems to be very difficult to motivate them to play the academic/scholarly/professional game because they regard even the most venerable of traditions and institutions as absurd or silly. Consider that even the mind of the average professor appears to them like the mind of the average bricklayer would appear to the professor.
IQ over 188
In all of history only about a dozen people have been this smart. Zietsman says: "I know of only one case for sure. William James Sidis lectured Harvard mathematicians on four-dimensional mathematics at age 11 and was a professor of mathematics at Rice University at age 14. "He easily mastered many more languages than the then ‘world record’ of around 40. He would do the entire New York Times crossword in his head.
"Because of his eccentricities, academics and the press mercilessly hounded him. At the age of 22 he published a book discussing black holes a full 15 years before Nobel laureate astrophysicist Subrahmanyan Chandrasekhar thought of them. “He eventually refused to do anything academic or have anything to do with academic society. Who knows what these people think about the rest of humanity?”
That would be 7000 freaks roaming the Earth 
