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Heredity and Intelligence
A History of the Abuse of Science
Naturalistic Fallacy
• "Ought" and "Is"
• Claims containing the concepts of "ought" or
"should" or similar obligations do not
generally follow from purely descriptive
claims.
• The naturalistic fallacy occurs when a
description of a situation is taken to provide
sufficient justification for creating or accepting
some duty or obligation.
Socrates
Socrates
• “…you are brothers, yet God has framed you
differently. Some of you have the power of command,
and in the composition of these he has mingled gold,
wherefore also they have the greatest honor; others
he has made of silver, to be auxiliaries; other again
who are to be husbandmen and craftsmen he has
composed of brass and iron; and the species will
generally be persevered in the children…An oracles
says that when a man of brass or iron guards the
State, it will be destroyed.”
Carolus Linneaus
• 1735 Carolus Linnaeus
“The Father of Taxonomy”,
offers first systematic
organizational schema to
understand the variety of life
in the natural order, which is
the basis of taxonomical
nomenclature.
Physical Differences
• Early attempts to understand
intelligence utilized unrefined
examinations of group differences
among people’s physical structure.
Investigators primarily examined these
areas by studying group averages for
skull capacity or actual brain size.
Phrenology
Body Morphology
Morphological assessments: From
the head to the body
• Phrenology (Gall, early 1800s) – skull shape = personality
• Sheldon’s body types (1950)
– Based on photographs of all incoming freshmen at Ivy league
schools in the 1930s
– Endomorph – jolly/happy, lazy
– Mesomorph – dominant, athletic
– Ectomorph – smart, shy
• Body type and criminality (Lombroso)
One Species, or Two?
• Monogeny
– The belief that all
humans belong to a
single species
– Difference such as
skin color, size,
culture are
superficial.
• Polygeny
– The belief that what
we perceive as racial
differences are in
fact different species
of human.
Louis Agassiz
• “There are upon earth different races of men,
inhabiting different parts of its surface, which
have different physical characters; and this
fact…presses upon us the obligation to settle
the relative rank among these races, the
relative value of the characters peculiar to
each, in a scientific point of view… As
philosophers it is our duty to look it in the
face.” (1850)
Samuel George Morton (1799
-1851)
Samuel George Morton
• Morton (1799 -1851) was Philadelphia
physician who collected and examined1,849
skulls of Americans. Most of these skulls
came from the various Native American tribes
that had once inhabited the land. Morton
believed that a ranking of the races could be
established objectively by looking at the
cranial capacity of the skulls. He used his
detailed research on cranial capacity to
support his theory of intellectual superiority of
different racial groups.
Samuel George Morton
• Stephen Jay Gould (1981) criticized his work with
four general problems:
– (1) He chose to include/delete sub-samples of skulls form his
calculations based on how they fit his theory;
– (2) He measured skull capacity with seeds which is
inaccurate and subject to bias; re-measurements with more
precise tools indicated that Caucasians were typically overestimated and other groups were underestimated;
– (3) He assumed that cranial size indicated intelligence and
didn’t considered the impact of one physical stature or
gender on the skull size;
– (4) He miscalculated rounding estimates that consistently
favored his hypothesis.
Morton’s Measurements
• Morton cared
about accuracy.
• Started by using
mustard seed.
• Changed to
using lead
pellets because
they were more
exact.
• Still got it wrong.
Dr. Paul Broca (1824-1880)
Dr. Paul Broca (1824-1880)
• Broca was a chief of surgery at a major
Parisian hospital who was interested in
the variations found among people’s
skeletal structures, particularly their
skulls. He developed several
instruments for measuring these
variations.
Dr. Paul Broca (1824-1880)
• Dr. Broca’s examination of brain size
was influenced by his desire to
demonstrate physical evidence for his
belief that Caucasian males were
intellectually superior to women and
men of other races.
For example:
• When Broca found that criminals mean
brain size was larger than honest
people’s average brain size, he
dismissed this information stating that
the executions caused the brain
structure to change or that the mean
age at death was younger.
More Examples
• When Gratiolet (an opponent of the belief that
brain size was correlated with intelligence)
indicated that French brains were smaller
than German brains, Broca correctly adjusted
the German brain sizes to account for
differences in body stature.
• However, he did not use this type of
adjustment when he examined the
differences between men and women’s brain
sizes.
Charles Darwin
The End of Polygeny
• Darwin’s theory of evolution posits
a common ancestor for all humans,
thus eliminating the possibility of
claiming that different races are
separate species.
Darwin’s Theory
• Three major principles:
1. heredity
• characteristics are passed from one generation to the
next
2. variability
• characteristics vary across members of a species
• some individuals will be more successful in their
environment than others
• demand for resources produces selective pressure
Darwin’s Theory
• Three major principles:
3. natural selection
• how species change, or evolve, over time
• only those members of a species able to
compete successfully for limited resources
will survive and reproduce
Social Darwinism
• The general misapplication of Darwinian
principles to society in order to justify
the social order.
– Spencer
– Galton
– Sumner
Sociology
• Sociology needed a theoretical structure.
Natural Selection provided a basis on which
to explain why societies have taken the forms
they have.
• British popular philosopher Herbert Spencer
(1820-- 1903) wrote extensively on the bases
of many social sciences. He is the person
who coined the term “Survival of the Fittest,”
in 1858 the year before the publication of the
Origin of Species.
Herbert Spencer (1820-1903)
Argues that domains of the
universe are subject to
objective laws and that the
goal of science is to discover
the principles of morphology
and physiology of all organic
and superorganic forms.
Argues that sociology is to
discover the universal and
enduring properties of human
social organization.
Selected Bibliography
The Proper Sphere of Government (1843).
Social Statics (1851).
First Principles, 1862.
Principles of Biology, 2 vols (1864-1867).
The Principles of Psychology, 2 vols (1870-1872)
The Study of Sociology (1874).
The Principles of Sociology, 3 vols (1882-1898).
The Man versus the State (1884).
The Factors of Organic Evolution (1887).
The Principles of Ethics, 2 vols (1892).
Herbert Spencer
was a prolific
writer.
Social Darwinism
Once discovered, people should obey the
laws of societal evolution and resist trying to
create, via state and legal mechanisms,
societal forms that transgress objective
societal laws.
Argument attempts to scientize laissez-fair
political ideology.
Spencer took the standard classical liberal
view of freedom:
Individuals should satisfy needs and desires
without interfering with the needs and desires
of others.
Individuals should be free as possible from
external regulation.
Moral law and laissez-faire capitalism are
thus co-extensive; both reflect biological laws
of survival of the fittest—the eternal struggle
among species.
Francis Galton (1822-1911)
Francis Galton
(1822-1911)
The life of Galton
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Born on Feb. 16, 1822, in Birmingham
Younger relative of Darwin
Child prodigy, independently wealthy, very poor student
Birmingham Medical School, doesn’t finish
Trinity College, Cambridge, medicine (1840), doesn’t finish
Cambridge, mathematics, doesn’t finish
Inherited a fortune (1844)
Noted explorer, geographer, meteorologist, balloonist, biological
researcher… and psychologist
• Became interested in individual differences at Cambridge
• Hereditary Genius (1869) eminence and intelligence are inherited
• Coined the word ‘eugenics’
Galton’s Contributions and
Influence
• Developed both intelligence tests and statistical
correlation
• Fingerprints: classified into ‘loops’, ‘arches’ and ‘whorls’
• Self-report questionnaires in psychology
• Questionnaires on mental imagery
• Word-association studies (cf. Psychoanalysis)
• Beauty maps of Britain (?)
• Influenced geography, meteorology, biology, statistics,
criminology and psychology
Hereditary Genius
• Galton drew on Darwin’s ‘Origin of
Species…’
– most important human evolutionary
characteristics = intellectual and psychological
• Noted that eminence ran in families =
inherited
Conceptualization of
Intelligence
• Our knowledge of the environment reaches
us through the senses (from John Locke)
• Therefore, those with more acute sensory
processes should be more intelligent
• Created tests of sensory discrimination and
motor coordination to assess mental function
Heredity is Key
• Human abilities are genetically
determined and the human species can
be improved through controlled
breeding practices
• I.e., Eugenics.
Hereditary Genius
•
Three pieces of ‘evidence’:
1. The Normal Distribution.
Quetelet had already shown height, etc. =
normally distributed.
2. Pedigrees of Genius.
Imperfect, but clear tendency for relatives to
excel and excel in similar fields
3. Adoptive vs Biological Relatives Studies.
Adopted “nephews” of Popes did not grow up
to be eminent
Correlation and regression
• Galton sought to express strengths of hereditary
relationships mathematically
- noticed tendencies (e.g height)
- cast various measurements into scatter plots
- observed regression towards the mean
- Noted steepness of any regression line
varied directly with strength of the relationship between
two variables
- Correlation
refined by Karl Pearson (Pearson’s r)
Eugenics
• Galton had a utopian vision
• ‘Eugenics’ = improving human race via
selective breeding
• Eugenic parents to be identified via
intelligence tests administer to all
Eugenics
• Measures of Intelligence :
– head size: power of the brain indicated
by its size
– reaction time: neurological efficiency
related to speed
– sensory acuity: retarded people (and
women!) less likely to feel pain/be able to
discriminate tea and coffee
• IQ tests not meaningful until Alfred Binet
(1905)
Cyril Burt
• Intelligence is strictly inherited
• No influence of teaching, training, or
environment
• Thus, income levels are determined by
intelligence, not environment
• Unfortunately, it appears as though old
Cyril manufactured much of his data.
Hereditarianism Today
•Hereditarians (Galton, Arthur Jensen,
Rushton, Hernnstein and Murray)
What’s Wrong?
• What went wrong in the thinking of the
hereditarianists?
– Naturalistic Fallacy.
– Darwinian Principles.
(Mis)interpreting Darwin
• Two common errors:
1. assuming that evolution means
“progress”
• Or, as species evolve, they improve
• Evolution simply means change and
adaptation to an environment
• Not “better,” but “better adapted”
(Mis)interpreting Darwin
• Two common errors:
2. “survival of the strongest”
• fit simply means best able to
survive and reproduce in the
environment
False Assumptions
• Reification - “Intelligence” actually represents
a complex, multifaceted set of human
aptitude, yet it is typically treated as a unitary
entity.
• Ranking - Our propensity to place arbitrary
order to complex variations.
• Reification & Ranking are both manifested in
our societies effort to represent intelligence
with one number such that the numbers can
be used to rank people’s worthiness.
Group Differences in IQ
IQ Changes
– Worldwide improvement in IQ scores
• 3pts. per decade
• Hard to account for this change
genetically
• Why?