"The Bell Curve" and Controversies over Race and IQ
The normal distribution is often called a "mound-shaped" distribution or a "bell curve." The connection between the two is that bells were once formed by pouring molten metal over a mound of sand.
Statistics textbooks often use IQ as an example of a "trait" that is normally distributed. IQ stands for "intelligence quotient," a single number based on a test defined as an "intelligence test." It is supposed to represent the "general intelligence" of an individual. Of course, many people-- including the psychologist Howard Gardner -- have questioned the idea that such a thing exists.
Here is a short, informal video from the Neurodivergent Rebel vlog:
There are MANY Types of Intelligence - The Problem with IQ
Links to an external site.
The original IQ tests were constructed to help teachers determine how best to help students learn. That soon changed. For over a century, IQ tests have been constructed and interpreted mainly to institutionalize racism and justify class divisions.
Tests like the Stanford-Binet were "standardized" by making sure that scores corresponded with teachers' or researchers' subjective estimate of students' abilities. They judged boys to be smarter than girls, and white people (from northern and western Europe) to be smarter than black people (or immigrants from southern or eastern Europe). They added and removed questions from their "intelligence" tests to make sure that white boys did well on them.
In the 1930s, it became unfashionable to assume women to be less intelligent than men. The tests were "re-normed" so that the average scores for women and men would be the same. To this day, the tests have never been re-normed to be non-racist.
IQ scores are normally distributed because the test is "normed" to be that way. The test makers ASSUME that a few people are exceptionally "smart" and a few are exceptionally "stupid" and most are "normal." Whether or not that is true depends on what you think intelligence is -- or if you think "general intelligence" exists at all.
The African-American psychologist Dr. Robert Williams was a leading critic of IQ tests. In 1972, he presented to the American Psychological Association his "Black Intelligence Test of Cultural Homogeneity" (BITCH-100). His presentation sharply exposed and ridiculed the way IQ tests have been socially constructed to incorporate specific cultural assumptions and expectations.
In 1994, several Harvard professors published a book called "The Bell Curve" that was widely criticized (and debunked) as a racist misuse of statistics. One prominent critic was Dr. Steven Jay Gould - see this video:
Francis Galton (1822-1911) is recognized as one of the founders of statistics. He believed that practically every human trait (including intelligence, temperament and more) followed a normal distribution. For Galton, statistics was a way to justify a program he called "eugenics." This meant selective breeding of "superior" people and selective elimination of "inferior" ones. He was an early example of what came to be known as "scientific racism."
References:
Gardner, H. (1983). Frames of mind: The theory of multiple intelligences. New York,NY: Basic Books.
Saini, Angela. (2019). Superior: The return of race science. Boston: Beacon Press.
Tucker, William H. (1994). The science and politics of racial research. University of Illinois Press.