Todd Rose, director of the “Mind, Brain, and Education” program at the Harvard Graduate School of Education, has written a brilliant and important new book titled The End of Average.

In it he argues that our notion of average, when applied to human beings, is terribly misguided. The belief that variation can be summarized using measures of center is often erroneous, especially when describing people. The “average person” does not exist, but the notion of the “Average Man” is deeply rooted in our culture and social institutions.

Sometimes variation—individuality—is the norm, with no meaningful measure of average. Consider the wonderful advances that have been made in neuroscience over the past 20 years or so. We now know so much more about the average brain and how it functions. Or do we? Some of what we think we know is a fabrication based on averaging the data.

In 2002, Michael Miller, a neuroscientist at UC Santa Barbara, did a study of verbal memory using brain scans. Rose describes this study as follows:

One by one, sixteen participants lay down in an fMRI brain scanner and were shown a set of words. After a rest period, a second series of words was presented and they pressed a button whenever they recognized a word from the first series. As each participant decided whether he had seen a particular word before, the machine scanned his brain and created a digital “map” of his brain’s activity. When Miller finished his experiment, he reported his findings the same way every neuroscientist does: by averaging together all the individual brain maps from his subjects to create a map of the Average Brain. Miller’s expectation was that this average map would reveal the neural circuits involved in verbal memory in the typical human brain…

There would be nothing strange about Miller reporting the findings of his study by publishing a map of the Average Brain. What was strange was the fact that when Miller sat down to analyze his results, something made him decide to look more carefully at the individual maps of his research participants’ brains… “It was pretty startling,” Miller told me. “Maybe if you scrunched up your eyes real tight, a couple of the individual maps looked like the average map. But most didn’t look like the average map at all.”

The following set of brain scans from Miller’s study illustrates the problem:

As you can see, averaging variation in cases like this does not accurately or usefully represent the data or the underlying phenomena. Unfortunately, this sort of averaging remains common practice in biology and social sciences. As Rose says, “Every discipline that studies human beings has long relied on the same core method of research: put a group of people into some experimental condition, determine their average response to the condition, then use this average to formulate a general conclusion about all people.”

This problem can be traced back to Belgian astronomer turned social scientist Adolphe Quetelet in the early 19th century. Quetelet (pronounced “kettle-lay”) took the statistical mean down a dark path that has since become a deep and dangerous rut. Sciences that study human beings have fallen into this rut and become trapped ever since. Many of the erroneous findings in these fields of research can be traced this fundamental misunderstanding and misuse of averages. It’s time to build a ladder and climb out of this hole.

When Quetelet began his career as an astronomer in the early 19th century, the telescope had recently revolutionized the science. Astronomers were producing a deluge of measurements about heavenly bodies. It was soon observed, however, that multiple measurements of the same things differed somewhat, which became known as the margin of error. These minor differences in measurements of physical phenomena almost always varied symmetrically around the arithmetic mean. Recognition of the “normal distribution” emerged in large part as a result of these observations. When Quetelet’s ambition to build a world-class observatory in Belgium was dashed because the country became embroiled in revolution, he began to wonder if it might be possible to develop a science for managing society. Could the methods of science that he learned as an astronomer be applied to the study of human behavior? The timing of his speculation was fortunate, for it coincided with the 19th century’s version of so-called “Big Data” as a tsunami of printed numbers. The development of large-scale bureaucracies and militaries led to the publication of huge collections of social data. Quetelet surfed this tsunami with great skill and managed to construct a methodology for social science that was firmly built on the use of averages.

Quetelet thought of the average as the ideal. When he calculated the average chest circumference of Scottish soldiers, he thought of it as the chest size of the “true” soldier and all deviations from that ideal as instances of error. As he extended his work to describe humanity in general, he coined the term the “Average Man.”

This notion of average as ideal, however, was later revised by one of Quetelet’s followers—Sir Francis Galton—into our modern notion of average as mediocre, which he associated with the lower classes. He believed that we should strive to improve on the average. Galton developed a ranking system for human beings consisting of fourteen distinct classes with “Imbeciles” at the bottom and “Eminent” members of society at the top. Further, he believed that the measure of any one human characteristic or ability could serve as a proxy for all other measures. For example, if you were wealthy, you must also be intelligent and morally superior. In 1909 Galton argued, “As statistics have shown, the best qualities are largely correlated.” To provide evidence for his belief, Galton developed statistical methods for measuring correlation, which we still use today.

Out of this work, first by Quetelet and later by Galton, the notion of the Average Man and the appropriateness of comparing people based on rankings became unconscious assumptions on which the industrial age was built. Our schools were reformed to produce people with the standardized set of basic skills that was needed in the industrial workplace. In the beginning of the 20th century, this effort was indeed an educational reform, for only six percent of Americans graduated from high school. Students were given grades to rank them in ability and intelligence. In the workplace, hiring practices and performance evaluations soon became based on a system of rankings as well. The role of “manager” emerged to distinguish above-average workers who were needed to direct the efforts of less capable, average workers.

I could go on, but I don’t want to spoil this marvelous book for you. I’ll let an excerpt from the book’s dust cover suffice to give you a more complete sense of the book’s scope:

In The End of Average, Rose shows that no one is average. Not you. Not your kids. Not your employees or students. This isn’t hollow sloganeering—it’s a mathematical fact with enormous practical consequences. But while we know people learn and develop in distinctive ways, these unique patterns of behaviors are lost in our schools and businesses which have been designed around the mythical “average person.” For more than a century, this average-size-fits-all model has ignored our individuality and failed at recognizing talent. It’s time to change that.

Weaving science, history, and his experience as a high school dropout, Rose brings to life the untold story of how we came to embrace the scientifically flawed idea that averages can be used to understand individuals and offers a powerful alternative.

I heartily recommend this book.

Take care,