Intelligence is a person's capacity to (1) acquire knowledge (i.e. learn and understand), (2) apply knowledge (solve problems), and (3) engage in abstract reasoning.  It is the power of one's intellect, and as such is clearly a very important aspect of one's overall well-being.  Psychologists have attempted to measure it for well over a century.

Intelligence Quotient (IQ) is the score you get on an intelligence test. Originally, it was a quotient (a ratio):  IQ= MA/CA x 100 [MA is mental age, CA is chronological age]. Today, scores are calibrated against norms of actual population scores.

• Under 70 [mentally retarded] -- 2.2%
• 70-80 [borderline retarded] -- 6.7%
• 80-90 [low average] -- 16.1%
• 90-110 [average] -- 50%
• 110-120 [high average] -- 16.1%
• 120-130 [superior] -- 6.7%
• Over 130 [very superior] -- 2.2%

Descriptive statistics

To understand IQ and the research involving IQ, we need to understand the basics of descriptive statistics:

1.  The normal curve.  This curve, also called the bell-shaped curve, is an idealized version of what happens in many large sets of measurements:  Most measurements fall in the middle, and fewer fall at points farther away from the middle.  Here, most people score near 100 (the average), and much less people score very high or very low.

2.  The mean.  The mean is just the average.  The sum of everyone’s IQ scores, divided by the number of scores, is the mean, which was originally set at 100 by agreement.

3.  The standard deviation.  The standard deviation is like the average degree to which scores deviate from the mean.  For our purposes, just know that 1 standard deviation above and below the mean [85 to 115] contains 68% of all the scores, 2 sd [70 to 130] contains 95%, and 3 sd [55 to 145] contains 99.7%

To understand the next discussion, we need to know about correlation.  Correlation is what you are doing when you compare two sets of measurements (each set is called a variable).  If you were to measure everyone’s height and weight, you could then compare heights and weights and see if they have any relationship to each other -- any co-relation, if you will.  Of course, the taller you are, generally speaking, the more you weight.  But it is obviously not a perfect co-relation, because some people are thin and some are fat.

A perfect correlation is +1.  An example would be the volume of water vs the weight of water.

Perfect correlation can also be -1.  An example would be the amount of ink left in your printer vs the amount of ink used up.

Most things have a correlation of 0.  An example would be your height vs your SAT score.

In psychology, we are generally impressed by correlations of .3 and higher.  .8 or .9 blows us away.

But one thing correlation cannot tell you is what causes what.  Your grades and your SATs correlate a little bit -- but which causes which?  Odds are there is something else that causes two things to correlate.

Is it genetic or environmental?

Here are a few correlations to ponder, between one person's IQ and anothers:

So intelligence clearly has a powerful genetic component.  But we can also see a number of environmental aids and hindrances:  A stimulating environment, parental encouragement, good schooling, specific reasoning skills, continued practice, and so on, certainly help a person become more intelligent.  Likewise, there are certain biological factors that are nevertheless environmental:  prenatal care, nutrition (especially in early childhood), freedom from disease and physical trauma, and so on.

All of these are important and cannot be ignored -- especially when these are the things we can most easily do something about!  But I do believe that something better than half of intelligence is accounted for by genetics.  And this is, to put it simply, a matter of brain efficiency.  If your brain is well-developed, free from genetic defects, free from neurochemical imbalances, then it will work well, given a decent environment.  But no matter how good your environment, if you are forced to rely on “bad equipment,” it will be much more difficult to attain high intelligence.

Most of the normal curve of intelligence, I believe, is due to a variety of physiological impairments of brain efficiency, such as that resulting from malnourishment, prenatal trauma, chromosomal damage, and, most often, simple inheritance of certain neurochemical makeups.  These stretch what would otherwise be a much “tighter” curve out to the low end.

The great majority of us have fairly healthy brains.  A very few have particularly healthy brains.  It would seem that having particularly healthy brains would be a fantastic aid to one’s “fitness,” so I can only guess that not being too bright must be even better!

Different kinds of intelligences

Is intelligence one thing (referred to as g)?  Many researchers believe it is.  Or is it many things.  Some suggestions include the following:

• Verbal, numerical, spatial, reasoning, fluency, perceptual speed...
• Fluid vs. crystallized (Cattell)...
• Linguistic, musical, logical-mathematical, spatial, bodily-kinesthetic, intrapersonal, interpersonal (Gardner)...

Social issues

A very  touchy subject is group differences in intelligence.  It is certainly conceivable that some groups have higher or lower average intelligence than others, whether through environmental or genetic causes.  But groups don’t really have intelligence, individuals do.  Averages are fictions -- convenient summaries of data -- and no individual need reflect that fiction.  So the debate would be only of scientific interest, were it not for the fact that so many people judge individuals by means of stereotypes.  This in itself is an example of poor thinking!

• 0 - 20  (profound) -- needs nursing care
• 20 - 35  (severe) -- can learn to talk and develop health habits
• 35 - 50  (moderate) -- second grade, needs sheltered care
• 50 - 70  (mild) -- educable to the sixth grade, minimally self-supporting

Difficulties with measuring intelligence

Finally, there’s the question of intelligence testing.  I think it has come a long way, but it has a long way to go as well.  I hope to see it become more inclusive of non-academic thinking, and to become less tied to prior learning.  The bigger problem with testing, however, is what we do with the results:  People are far too prone to take test scores at face value, without looking at a broader selection of information about a person’s abilities.  They are also far too likely  to generalize to non-intelligence issues.  We should certainly not use intelligence tests carelessly when deciding children's’ educations or adult’s  careers.

Cultural variables

Try these questions:

1.  How many days does it take for a chicken egg to hatch?
2.  What color is a Holstein cow?
3.  How many stomachs does a cow have?
4.  Does a bull have a cud?
5.  Is a rooster necessary for a hen to lay eggs?

The answers:  21; black and white; 4; yes; and no, unless you want fertilized eggs.  These are easy questions if you grew up on a farm!

Other examples:  The famous "chittlin's" test, biased towards black Americans.  It is named for the question:  "What are chittlin's?"  Answer:  Pig's intestines, cleaned, soaked, and fried (originally called chitterlings).  Or you could bias towards other groups by asking "What is tripe?" (an English dish consisting of sautéed ox stomach strips) or "What is haggis?" (a Scottish dish consisting of a sheep's stomach filled with a porridge made of oats and various sweetmeats.)

It becomes even more dramatic when we look at people very different from ourselves, such as children growing up in the wilds of Papua-New Guinea.  Some of the biases working against them might include...

1.  Use of paper and pencil. Problems are often presented in the form of diagrams; answering often requires x-ing, circling, underlining, etc.  Not easy for someone unfamiliar with paper and pencil!
2.  Use of pictorial material.  Pictures, especially as printed on paper, use highly conventional symbols, e.g. cutouts of pots, huts, etc. were thought to be pieces of cardboard, rather than the  objects they represented.  when placed into a scene, they began to make sense.
3.  Use of non-representational drawings.  Geometric figures, colored patterns, mazes, etc., lack meaning to many people.  Artistic patterns are only understood in context.
4.  Appreciation of spatial relations.  Our emphasis on three-dimensions at right angles is culturally specific. Other cultures emphasize rounded figures more.
5.  Manipulation.  If you lack experience with blocks, puzzles, pieces of cardboard, etc., you also lack a feel for them and may be clumsy with them, leading the tester to conclude that you are "dumb."

How are a pair of scissors and a copper pan alike?

One point answer:  They are both household utensils.
Two point answer:  They are both made of metal.

Which doesn't belong:  clam, pig, oven, rose.

The correct answer is the oven, because the rest are living things.
But a child may say rose, since the others relate to making dinner.
Or the clam, since clams live in the water, and the rest live on land.

Not only can different answers reflect different social or cultural backgrounds; they may also reflect originality and novel outlook.

In certain IQ tests, the child is given two points for "categorical" answers, one point for "descriptive" answers, but no points for "relational" answers.  So, in response to "How are a cat and a mouse alike?" you get two points for "they are both animals," one point for "they both have tails," and nothing at all if you say "they both live in houses."

With drawings of a boy, an old man, and a woman (the latter two wearing hats), children were asked "Which go together?"  "Good" answers include the boy and the man, because they are both male, or the man and the woman because they are both adults.  Less points are awarded to "the man and the woman, because they are both wearing hats."  and no points are gained for "the boy and the old man, because the boy can help the old man walk," which strikes me as the most creative answer!

Disembedded thought

The most important of all the confusing variables, I believe, is the problem of disembedded thought.  Disembedded thought is Margaret Donaldson's term for thought that takes place in a contextual vacuum:  It takes years of practice to get to a point where one is comfortable with abstract questions.  Answering what appear to be meaningless questions is rejected by people of many cultures, by most young children, and by many people with different "cognitive styles."  It is, in fact, a talent peculiar to us (i.e. educated western adults, and a few others).  Many others will spend their creative energies not at solving the problem, but at trying to figure out why you would ask such a strange question to begin with.

IQ tests, especially in the past, have been (1) competition-oriented (with motivation to answer quickly and accurately assumed), (2) upper-middle class oriented, and (3) western culture-oriented (especially in regards to the thought process associated with science and technology).  It should be understood, however, that psychologists have been working hard at eliminated these various biases, or at least reducing them, and that IQ tests today are at least relatively culturally fair.  They are certainly very reliable, and do in fact related well to success in school and western society -- i.e. the culture and institutions that share the values of these tests.

Using intelligence tests

There is one more problem with IQ tests, this time not about making them or giving them, but about using them:

There was an experiment by Rosenthal in which school teachers were casually told at the beginning of the school year that certain students (mentioned by name) were "spurters," that, according to some tests designed to measure "spurting," they would blossom in the coming year.  Actually no such test had been given.  In fact, no such test exists.  The information was actually given about 20% of the students, chosen at random.

These kids no only did well academically (which we might expect, with teachers having some control over that), but actually increased their IQ test scores!

The same, incidentally, happens with rats:  Graduate students told that certain rats had been bred for intelligence found that they did indeed do better at learning mazes -- even though the information was false!

This is a form of experimenter bias, of course, and part of the reason we have double blinds in experiments.  but in the broader, social arena, we call this the self-fulfilling prophecy, or the labelling effect.  It is clear that we should take children as individuals and give them whatever education they can handle.  Unfortunately, that is costly.

© Copyright 2003, C. George Boeree