All the early influences on differential psychology mentioned so far came
from philosophers. None was an empirical scientist. Darwin was, of course, but
Darwinian ideas were introduced into psychology by Herbert Spencer, a pro­
fessional philosopher. The empirical study of mental ability and individual dif­
ferences could not begin until someone took up the methods of empirical
science, that is, asking definite questions of nature and discovering the answers
through analysis of data based on systematic observation, objective measure­
ment, and experimentation. The first person to do this was the Victorian eccen­
tric, polymath, and genius Sir Francis Galton (1822-1911).3 Galton was Charles
Darwin’s younger half-cousin—half-cousin because they had only one grand­
parent in common, Erasmus Darwin, a noted physician, physiologist, naturalist,
and poet. Born into a prominent and wealthy family, Galton was a child prodigy,
who could read and write before the age of four. He intensely disliked school,
however, and his parents transferred him from one private boarding school to
another, each as boring and frustrating to him as the others, and he begged his
parents to let him quit. In his Memories o f My Life (1908), written when he was
86, he still complained of his unsatisfying school experience. At age fifteen, he
was sent away to college, which offered more challenge. To satisfy his parents’
ambition that he follow in his eminent grandfather’s footsteps and become a
physician, he entered medical school. There he soon discovered that the basic
sciences—physics, chemistry, biology, and physiology—were far more to his
liking than medical practice. So he left medical school for Cambridge Univer­
sity, there to major in mathematics in preparation for a career in science.

Soon after Galton graduated, at age twenty-one, his father died, and Galton
received a large inheritance that made him independently wealthy for the rest
of his very long life. It allowed him to pursue his extremely varied interests
freely in all things scientific. His enthusiastic and catholic curiosity about natural
phenomena drove him to became perhaps the greatest scientific dilettante of all
time. Because he was also a genius, he made original contributions to many
fields, some of them important enough to be accorded chapters in books on the
history of several fields: criminology, eugenics, genetics, meteorology, psy­
chology, and statistics. He first gained fame in geography, as an explorer, ex­
pertly describing, surveying, and mapping previously unexplored parts of Africa.
For this activity, his name is engraved on the granite facade of the Royal Ge­
ographical Society’s building in London, along with the names of the most
famous explorers in British history. (His fascinating book  The Art o f Travel
[1855] was a long-time best seller and went through nine editions.) He also
made contributions to meteorology, inventing isobar mapping, being the first to
write a daily newspaper weather report, and formulating a widely accepted the­
ory of the anticyclone. He made other original contributions to photography,
fingerprint classification, genetics, statistics, anthropology, and psychometrics.
His prolific achievements and publications brought worldwide recognition and
many honors, including knighthood, Fellow of the Royal Society, and several
gold medals awarded by scientific societies in England and Europe. As a famous
man in his own lifetime, Galton also had what Hollywood calls “ star quality.”

Biographies of Galton also reveal his charming eccentricities. His profuse
intellectual energy spilled over into lesser achievements or activities that often
seem trivial. He was almost obsessed with counting and measuring things (his
motto: “When you can, count!” ), and he devised mechanical counters and other
devices to help in counting and tabulating. He loved data. On his first visit to
a city, for example, he would walk around with a small, hand-held mechanical
counter and tally the number of people passing by, tabulating their character­
istics—tall, medium, short; blond, brunette, redhead—separately for males and
females, the latter also rated for attractiveness. To be able to manage all these
data while walking about, he had his tailor make a special vest with many little
pockets, each one for a particular tabulated characteristic. He could temporarily
store the data from his counters by putting into designated pockets the appro­
priate number of dried peas. Back in his hotel room, he counted the peas in
each pocket and entered the numerical results in his notebook for later statistical

He devised an objective measure of the degree to which a lecturer bored the
audience, and tried it out at meetings of the Royal Society. It consisted of
counting the involuntary noises—coughs, feet shuffling, and the like—that is­
sued from the audience, and, with a specially rigged protractor, he measured the
angle that listeners’ heads were tilted from a vertical position during the lecture.
A score derived from the data obtained with this procedure showed that even
the most eloquently written lecture, if read verbatim, was more boring than an
extempore lecture, however rambling and inelegant.

He also invented a special whistle (now called a Galton whistle), which is
familiar to many dog owners. Its high-frequency pitch is beyond humans’ au­
dible range and can be heard only by dogs and certain other animals. Galton
made a series of these whistles, ranging widely in pitch, and used them to find
the upper limits of pitch that could be heard by humans of different ages. To
compare the results on humans with the auditory capacities of many species in
the London Zoo, he would attach the whistles to the end of a tube that could
be extended like a telescope, so it could reach into a cage and direct the sound
right at the animal’s ear. While quickly squeezing a rubber bulb attached to one
end of the long tube to force a standard puff of air through the whistle attached
to the other end, he would note whether or not the animal reacted to a particular

In another amusing project, he used the mathematics of solid geometry to
figure out the optimal way to cut a cake of any particular shape and dimensions
into any given number of pieces to preserve the freshness of each piece. He
published his clever solution in a mathematics journal. There are many other
quaint anecdotes about Galton’s amazing scientific curiosity and originality, but
the several already mentioned should suffice to round out the picture of his
extraordinary personality.

Although he died (at age ninety) as long ago as 1911, his legacy remains
remarkably vivid. It comprises not only his many pioneering ideas and statistical
inventions, still in use, but also the important endowments, permitted by his
personal wealth, for advancing the kinds of research he thought would be of
greatest benefit to human welfare. He founded the Department of Eugenics (now
Genetics) at the University of London and endowed its Chair, which has been
occupied by such luminaries as Karl Pearson, Sir Ronald Fisher, and Lionel
Penrose; he furnished a psychological laboratory in University College, London;
he founded two prestigious journals that are still active,  Biometrika and  The
Annals o f Human Genetics’, and he founded (in 1904) the Eugenics Society
(recently renamed The Galton Institute), which maintains an extensive library,
publishes journals and books, and sponsors many symposia, all related to the
field now known as social biology.


Galton’s position in the history of behavioral science is stellar. He is ac­
knowledged as one of the two founding fathers of empirical psychology, along
with Wilhelm Wundt (1832-1920), who established the first laboratory of ex­
perimental psychology in 1879 in Leipzig. As Wundt is recognized as the father
of experimental psychology, Galton can certainly be called the father of differ­
ential psychology, including psychometrics and behavioral genetics. Each is now
a major branch of modern behavioral science. The leading historian of experi­
mental psychology, Edwin G. Boring (1950), drew the following interesting
contrast between the scientific personalities of Galton and Wundt:

Wundt was erudite where Galton was original; Wundt overcame massive obstacles
by the weight of his attack; Galton dispatched a difficulty by a thrust of insight.
Wundt was forever armored by his system; Galton had no system. Wundt was
methodical; Galton was versatile. Wundt’s science was interpenetrated by his
philosophy; Galton’s science was discursive and unstructured. Wundt was
interminably arguing; Galton was forever observing. Wundt had a school, a formal
self-conscious school; Galton had friends, influence and effects only. Thus, Wundt
was personally intolerant and controversial, whereas Galton was tolerant and ready
to be convicted of error, (pp. 461-62)

Wundt and Galton were the progenitors of the two main branches of scientific
psychology—experimental (Wundt) and differential (Galton). These two disci­
plines have advanced along separate tracks throughout the history of psychology.
Their methodological and even philosophical differences run deep, although
both branches embrace the scientific tradition of objective testing of hypotheses.

Experimental psychology searches for general laws of behavior. Therefore, it
treats individual differences as unwanted variance, termed “ error variance,”
which must be minimized or averaged out to permit the discovery of universal
regularities in the relation between stimulus and response. The method of ex­
perimental psychology consists of controlling variables (or treatment conditions)
and randomizing the assignment of subjects to the different treatments. The
experimental conditions are intentionally manipulated to discover their average
effects, unconfounded by individual differences. In general, the stimulus pre­
sented to the subject is varied by the experimenter, while the subject’s responses
are recorded or measured. But the data of primary interest to the experimental
psychologist consist of the averaged performance of the many subjects randomly
assigned to each condition.

Differential psychology, on the other hand, seeks to classify, measure, and
then explain the variety and nature of both individual and group differences in
behavioral traits as phenomena worthy of investigation in their own right. It uses
statistical analysis, such as correlation, multiple regression, and factor analysis,
applied to data obtained under natural conditions, rather than the controlled
conditions of the laboratory. Obviously, when human characteristics are of in­
terest, individual differences and many other aspects of behavior cannot feasibly
or ethically be controlled or manipulated by the investigator. Therefore, scien­
tists must study human variation as it occurs under natural conditions. During
the latter half of this century, however, a rapprochement has begun between the
two disciplines. Both experimental and correlational methods are being used in
the study of cognition.

G al to n ’s Methodological Contributions. Galton made enduring contribu­
tions to the methodology of differential psychology. He was the first to devise
a precise quantitative index of the degree of relationship, or  co-relation (as he
called it) between any two metric variables obtained from the same individuals
(or relatives) in a given population. Examples are individuals’ height and weight
or the resemblance between parents and children, or between siblings, in a given

In 1896, Karl Pearson (1857-1936), a noted mathematician, who became a
Galton disciple and has been rightly called the “ father of statistics,” revamped
Galton’s formulation of co-relation, to make it mathematically more elegant and
enhance its general applicability. Pearson’s formula yields what now is called
“ the Pearson product-moment coefficient of correlation.” In the technical lit­
erature, however, the word  correlation, without a modifier, always signifies
Pearson’s coefficient.4 (The many other types of correlation coefficient are al­
ways specified, e.g.,  intraclass correlation,  rank-order correlation,  tetrachoric
correlation,  biserial correlation,  point-biserial correlation,  partial correlation,
semipartial correlation,  multiple correlation,  canonical correlation, correlation
ratio, phi coefficient,  contingency coefficient,  tau coefficient,  concordance co­
efficient, and  congruence coefficient. Each has its specialized use, depending on
the type of data.) Pearson’s correlation is the most generally used. Universally
symbolized by a lower-case italic  r (derived from Galton’s term  regression), it
is a ubiquitous tool in the biological and behavioral sciences. In differential
psychology, it is absolutely essential.

Galton invented many other statistical and psychometric concepts and meth­
ods familiar to all present-day researchers, including the bivariate scatter dia­
gram, regression (related to correlation), multiple regression and multiple
correlation (by which two or more different variables are used to predict another
variable), the conversion of measurements or ranks to percentiles, standardized
or scale-free measurements or scores, various types of rating scales, the use of
the now familiar normal or bell-shaped curve (originally formulated by the great
mathematician Karl Friedrich Gauss [1777-1855]) as a basis for quantifying
psychological traits on an equal-interval scale, and using either the median or
the geometric mean (instead of the arithmetic mean) as the indicator of central
tendency of measurements that have a markedly skewed frequency distribution.

In his  Inquiries into Human Faculty and Its Development (1883), Galton
described an odd assortment of clever tests and techniques, devised mostly by
himself, for measuring basic human capacities, particularly keenness of sensory
discrimination in the different modalities, imagery, and reaction times to audi­
tory and visual stimuli. Although Galton’s use of gadgetry has been disparaged
as “ brass instrument psychology,” it was a seminal innovation—the  objective
measurement of human capacities. Compared with modern technology, of
course, Galton’s methods were fairly crude, sometimes even inadequate for their
purpose. His intense interest in human variation and his passion for quantitative
data, however, led him to apply his “ brass instrument” techniques to almost
every physical and mental characteristic that could be counted, ranked, or mea­

Galton obtained many types of data on more than 9,000 persons who, from
1884 to 1890, went through his Anthropometric Laboratory in London’s South
Kensington Science Museum. Each had to pay threepence to serve as subjects
for these tests and measurements. Unfortunately, Galton lacked the powerful
tools of statistical inference that were later developed by Karl Pearson (1857-
1936) and Sir Ronald A. Fisher (1890-1962), and therefore he could only draw
much weaker conclusions than the quality of his massive data really warranted.
He was dismayed that the measurements of sensory discrimination and speed of
reaction appeared to show so little relationship to a person’s level of general
mental ability (as indicated by educational and occupational attainments). It soon
became a widely accepted and long-lasting conclusion that the simple functions
assessed by Galton are unrelated to individual differences in the higher mental
processes, or intelligence. Galton’s “ brass instrument” approach to the study
of human abilities, therefore, was abandoned for nearly a century.

Recently, Galton’s original data have been analyzed by modern methods of
statistical inference.151 It turned out that his original hypotheses were largely
correct after all. R. A. Fisher’s method known as analysis o f variance revealed
highly significant differences between groups differing in educational and oc­
cupational level on Galton’s discrimination and reaction-time tests. Galton’s
scientific intuitions were remarkably good, but the psychometric and statistical
methods then available were not always up to the task of validating them.

Galton Introduces Genetics into Psychology. Galton’s most famous work,
Hereditary Genius (1869), was the forerunner of behavior genetics, nearly a
century before either the term or the field of behavior genetics came into being.
Galton was especially interested in the inheritance of mental ability. Because
there was then no objective scale for measuring mental ability, he devised an­
other criterion of high-level ability:  eminence, based on illustrious achievements
that would justify published biographies, encyclopedia articles, and the like. By
this criterion, he selected many of the most famous intellects of the nineteenth
century, whom he classed as “ illustrious,” and he obtained information about
their ancestors, descendants, and other relatives. His extensive biographical and
genealogical research revealed that the relatives of his illustrious probands were
much more likely to attain eminence than would a random sample of the pop­
ulation with comparable social background. More telling, he noticed that the
probability of eminence in a relative of an illustrious person decreased in a
regular stepwise fashion as the degree of kinship was more remote. Galton
noticed that the same pattern was also true for physical stature and athletic

Galton made other observations that gave some indication of the power of
family background in producing eminence. In an earlier period of history, it was
customary for popes to adopt orphan boys and rear them like sons, with all the
advantages of culture and education that papal privilege could command. Galton
noted that far fewer of these adopted boys ever attained eminence than did the
natural sons of fathers whose eminence was comparable to a pope’s. From such
circumstantial evidence, Galton concluded that mental ability is inherited in
much the same manner, and to about the same degree, as physical traits.

Galton further concluded that what was inherited was essentially a  general
ability, because eminent relatives in the same family line were often famous in
quite different fields, such as literature, mathematics, and music. He supposed
that this hereditary general ability could be channeled by circumstance or interest
into different kinds of intellectual endeavor. He also recognized special abilities,
or talent, in fields like art and music, but considered them less important than
general ability in explaining outstanding accomplishment, because a high level
of general ability characterized all of his illustrious persons. (Galton noted that
they were also characterized by the unusual zeal and persistence they brought
to their endeavors.) He argued, for example, that the inborn musical gift of a
Beethoven could not have been expressed in works of genius were it not ac­
companied by superior general ability. In Hereditary Genius, he summarized his
concept of general ability in his typically quaint style: “ Numerous instances
recorded in this book show in how small a degree eminence can be considered
as due to purely special powers. People lay too much stress on apparent spe­
cialities, thinking that because a man is devoted to some particular pursuit he
would not have succeeded in anything else. They might as well say that, because
a youth has fallen in love with a brunette, he could not possibly have fallen in
love with a blonde. As likely as not the affair was mainly or wholly due to a
general amorousness” (p. 64).

Ga l to n ’s Anecdotal Report on Twins. The use of twins to study the inher­
itance of behavioral traits was another of Galton’s important “ firsts.” He noted
that there were two types of twins, judging from their degree of resemblance.
“ Identical” twins come from one egg (hence they are now called monozygotic,
or MZ, twins), which divides in two shortly after fertilization. Their genetic
makeup is identical; thus their genetic correlation is unity (r = 1). And they are
very alike in appearance. “ Fraternal” twins (now called dizygotic, or DZ) come
from two different fertilized eggs and have the same genetic relationship as
ordinary siblings, with a genetic correlation of about one-half (on average). That
is, DZ twins are, on average, about one-half as similar, genetically, as MZ twins.
DZ twins are no more alike in appearance than ordinary siblings when they are
compared at the same age.

Galton was interested in twins’ similarities and differences, especially in MZ
twins, as any difference would reflect only the influence of environment or
nongenetic factors. He located some eighty pairs of twins whose close physical
resemblance suggested they were MZ, and he collected anecdotal data on their
behavioral characteristics from their relatives and friends and from the twins
themselves. He concluded that since the twins were so strikingly similar in their
traits, compared to ordinary siblings, heredity was the predominant cause of
differences in individuals’ psychological characteristics.

Because Galton obtained no actual measurements, systematic observations, or
quantitative data, his conclusions are of course liable to the well-known short­
comings of all anecdotal reports. Later research, however, based on the more
precise methods of modern psychometrics and biometrical genetics, has largely
substantiated Galton’s surmise about the relative importance of heredity and
environment for individual differences in general mental ability. But Galton’s
research on heredity is cited nowadays only for its historical interest as the
prototype of the essential questions and methods that gave rise to modern be­
havioral genetics. It is a fact that most of the questions of present interest to
researchers in behavioral genetics and differential psychology were originally
thought of by Galton. His own answers to many of the questions, admittedly
based on inadequate evidence, have proved to be remarkably close to the con­
clusions of present-day researchers. In the history of science, of course, the
persons remembered as great pioneers are those who asked the fundamental
questions, thought of novel ways to find the answers, and, in retrospect, had
many correct and fruitful ideas. By these criteria, Galton unquestionably quali­

Ga l to n ’s Concept of Mental Ability. Galton seldom used the word  intelli­
gence and never offered a formal definition. From everything he wrote about
ability, however, we can well imagine that, if he had felt a definition necessary,
he would have said something like  innate, general, cognitive ability. The term
cognitive clearly distinguishes it from the two other attributes of Plato’s triarchic
conception of the mind, the affective and conative. Galton’s favored term, men­
tal ability, comprises both general ability and a number of special abilities—he
mentioned linguistic, mathematical, musical, artistic, and memorial. General
ability denotes a power of mind that affects (to some degree) the quality of
virtually everything a person does that requires more than simple sensory acuity
or sheer physical strength, endurance, dexterity, or coordination.

Analogizing from the normal, bell-shaped distribution of large-sample data
on physical features, such as stature, Galton assumed that the frequency distri­
bution of ability in the population would approximate the normal curve. He
divided the normal curve’s baseline into sixteen equal intervals (a purely arbi­
trary, but convenient, number) to create a scale for quantifying individual and
group differences in general ability. But Galton’s scale is no longer used. Ever
since Karl Pearson, in 1893, invented the  standard deviation, the baseline of
the normal distribution has been interval-scaled in units of the standard devia­
tion, symbolized by c (the lower-case Greek letter sigma). Simple calculation
shows that each interval of Galton’s scale is equal to 0.696o, which is equivalent
to 10.44 IQ points, when the o of IQ is 15 IQ points. Hence Galton’s scale of
mental ability, in terms of IQ, ranges from about 16 to 184.

Galton was unsuccessful, however, in actually  measuring individual differ­
ences in intelligence. We can easily see with hindsight that his particular battery
of simple tests was unsuited for assessing the higher mental processes that peo­
ple think of as “ intelligence.” Where did Galton go wrong? Like Herbert Spen­
cer, he was immensely impressed by Darwin’s theory of natural selection as the
mechanism of evolution. And hereditary individual variation is the raw material
on which natural selection works by, in Darwinian terms, “ selection of the fittest
in the struggle for survival.” Also, Galton was influenced by Locke’s teaching
that the mind’s content is originally gained through the avenue of the five senses,
which provide all the raw material for the association of impressions to form
ideas, knowledge, and intelligence. From Darwin’s and Locke’s theories, Galton
theorized that, in his words, “ the more perceptive the senses are of differences,
the larger is the field upon which our judgement and intelligence can act”
{Human Faculty, 1883, p. 19). Among many other factors that conferred advan­
tages in the competition for survival, individual variation in keenness of sensory
discrimination, as well as quickness of reaction to external stimuli, would have
been positively selected in the evolution of human intelligence.

It seemed to Galton a reasonable hypothesis, therefore, that tests of fine sen­
sory  discrimination (not just simple acuity) and of reaction time to visual and
auditory stimuli would provide objective measures of individual differences in
the elemental components of mental ability, unaffected by education, occupation,
or social status. The previously described battery of tests Galton devised for this
purpose, it turned out, yielded measurements that correlated so poorly with com-
monsense criteria of intellectual distinction (such as election to the Royal So­
ciety) as to be unconvincing as a measure of intelligence, much less having any
practical value. Statistical techniques were not then available to prove the the­
oretical significance, if any, of the slight relationship that existed between the
laboratory measures and independent estimates of ability. Galton had tested
thousands of subjects, and all of his data were carefully preserved. When re­
cently they were analyzed by modern statistical methods, highly significant (that
is, nonchance) differences were found between the  average scores obtained by
various groups of people aggregated by age, education, and occupation.151 This
finding lent considerable theoretical interest to Galton’s tests, although they
would have no practical validity for individual assessment.

Binet and the F irs t Practical Test of Intelligence. At the behest of the Paris
school system, Alfred Binet in 1905 invented the first valid and practically useful
test of intelligence. Influenced by Galton and aware of his disappointing results,
Binet (1857-1911) borrowed a few of Galton’s more promising tests (for ex­
ample, memory span for digits and the discrimination of weights) but also de­
vised new tests of much greater mental complexity so as to engage the higher
mental processes—reasoning, judgment, planning, verbal comprehension, and
acquisition of knowledge. Test scores scaled in units of mental age derived from
Binet’s battery proved to have practical value in identifying mentally retarded
children and in assessing children’s readiness for schoolwork. The story of Bi­
net’s practical ingenuity, clinical wisdom, and the lasting influence of his test
is deservedly well known to students of mental measurement.171 The reason that
Binet’s test worked so well, however, remained unexplained by Binet, except
in intuitive and commonsense terms. A truly theory-based explanation had to
wait for the British psychologist Charles Spearman (1863-1945), whose mo­
mentous contributions are reviewed in the next chapter.

Galton on Race Differences in Ability. The discussion of Galton’s work in
differential psychology would be incomplete without mentioning one other topic
that interested him—race differences in mental ability. The title itself of his
chapter on this subject in  Hereditary Genius would be extremely unacceptable
today: “ The Comparative Worth of Different Races.” But Galton’s style of
writing about race was common among nineteenth-century intellectuals, without
(he slightest implication that they were mean-spirited, unkindly, or at all un­
friendly toward people of another race. A style like Galton’s is seen in state­
ments about race made by even such democratic and humanitarian heroes as
Jefferson and Lincoln.

Galton had no tests for obtaining direct measurements of cognitive ability.
Yet he tried to estimate the mean levels of mental capacity possessed by different
racial and national groups on his interval scale of the normal curve. His esti­
mates—many would say guesses—were based on his observations of people of
different races encountered on his extensive travels in Europe and Africa, on
anecdotal reports of other travelers, on the number and quality of the inventions
and intellectual accomplishments of different racial groups, and on the percent­
age of eminent men in each group, culled from biographical sources. He ven­
tured that the level of ability among the ancient Athenian Greeks averaged “ two
grades” higher than that of the average Englishmen of his own day. (Two grades
on Galton’s scale is equivalent to 20.9 IQ points.) Obviously, there is no pos­
sibility of ever determining if Galton’s estimate was anywhere near correct. He
also estimated that African Negroes averaged “ at least two grades” (i.e., 1.39a,
or 20.9 IQ points) below the English average. This estimate appears remarkably
close to the results for phenotypic ability assessed by culture-reduced IQ tests.
Studies in sub-Saharan Africa indicate an average difference (on culture-reduced
nonverbal tests of reasoning) equivalent to 1.43a, or 21.5 IQ points between
blacks and whites.8 U.S. data from the Armed Forces Qualification Test (AFQT),
obtained in 1980 on large representative samples of black and white youths,
show an average difference of 1.36a (equivalent to 20.4 IQ points)—not far
from Galton’s estimate (1.39a, or 20.9 IQ points).9 But intuition and informed
guesses, though valuable in generating hypotheses, are never acceptable as ev­
idence in scientific research. Present-day scientists, therefore, properly dismiss
Galton’s opinions on race. Except as hypotheses, their interest is now purely
biographical and historical.


3. The literature on Galton is extensive. The most accessible biography is by Forrest
(1974). Fancher (1985a) gives a shorter and highly readable account. A still briefer
account of Galton’s life and contributions to psychology is given in Jensen (1994a),
which also lists the principal biographical references to Galton. His own memoir (Galton,
1908) is good reading, but does not particularly detail his contributions to psychology,
a subject reviewed most thoroughly by Cyril Burt (1962). Galton’s activities in each of
the branches o f science to which he made original contributions are detailed in a collec­
tion o f essays, each by one o f fourteen experts in the relevant fields; the book also
includes a complete bibliography o f Galton’s published works, edited by Keynes (1993).
Fancher (1983a, 1983b, 1983c, 1984) has provided fascinating and probing essays about
quite specific but less well-known aspects o f Galton’s life and contributions to psychol­
ogy. Lewis M. Terman (1877-1956), who is responsible for the Stanford-Binet IQ test,
tried to estimate Galton’s IQ in childhood from a few of his remarkably precocious
achievements even long before he went to school. These are detailed in Terman’s (1917)
article, in which he concluded that Galton’s childhood IQ was “ not far from 200” (p.
212). One o f Galton’s biographers, Forrest (1974), however, has noted, “ Terman was
misled by Francis’ letter to [his sister] Adele which begins, ‘I am four years old.’ The
date shows that it was only one day short of his fifth birthday. The calculations should
therefore by emended to give an I.Q. of about 160” (p. 7). (Note: Terman estimated IQ
as 100  X  estimated Mental Age (MA)/Chronological Age (CA); he estimated Galton’s
MA as 8 years based on his purported capabilities at CA 5 years, so 100 x 8/5 = 160.)

(all from The g factor, the science of mental ability – Arthur R. Jensen,, chapter 1).

The Keynes book is: The Legacy of His Ideas  by Francis Galton; ed. Milo Keynes.

I found a review of it, here: Sir Francis Galton, FRS The legacy of his ideas. review

I was particular struck by this:

Some contributors  suggest  that  he spread  himself  too  thinly:  that  he did  too many
things and followed up too few. Perhaps  so, but many great  scientists have been
polymaths.  Could  it be something  more  insidious?  That  his major  work  has become
too politically incorrect  to mention?

I am much like Galton, except that im not that smart. I seem to be around 2.3sd above the white mean, but share his mental energy and diverse interests.