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Evolution and Psychology
While evolutionary ideas in one form or another trace back to the ancient
Greeks, it was not until 18th century that they became scientifically prominent
and were connected to psychology
Georges de Buffon 1707-1788
French naturalist, mathematician,
cosmologist
In his Histoire naturelle discusses a
concept similar to “common descent.”
However, did not see a close relationship
between humans and apes. Credited by
Darwin as being the first modern author
to treat evolution in a scientific spirit.
Herbert Spencer 1820-1903. Saw evolution as a progressive march toward perfection (his
view of survival of the fittest). Argued that societies must allow adequate freedom so that
more ‘fit’ individuals could succeed both socially and reproductively while less ‘fit’ would
fail, therefore leading to general ‘improvement’ in society and humanity, called social
Darwinism. Added learned adaptive associations to Lamarck’s list of acquired traits.
These adaptive associations would be reflected in instincts, habits, and reflexes. His
combo of associationism and evolution called evolutionary associationism.
Jean-Baptiste Lamarck 1744-1829.
Argued the inheritance of acquired
traits. Adaptive physical
characteristics acquired during one’s
lifetime passed along to offspring
making offspring more adaptive.
Darwinism
• Charles Darwin’s
1809-1882. Major
contribution was not
evolution itself; but
the mechanism by
which it operated:
Natural selection
• NS was also discussed
by Darwin’s
contemporary: Alfred
Russell Wallace
(1823-1913).
Part of Darwin’s inspiration in the development
of NS, was the writings of economist Thomas
Malthus (1766-1834) who argued that while food
resources increase arithmetically over time,
human population grew geometrically, thus
leading to an inevitable competition for scarce
resources.
Evolution: Basic Principles
Evolution: Change over time; decent with modification
Darwin said little about humans in
Origin of Species (1859), but
addressed the question later in
Descent of Man (1871) and The
Expressions of Emotions in Man and
Animals (1872). In Expressions, he
argued that human emotions were
related to the internal, biological
states that accompanied animal
behaviors associated with survival
and reproduction. For example,
when animals fight, they bare their
teeth in a threatening manner.
Humans ancestors probably did this
as well, but now there is no need for
the behavioral threat, but the
internal, biological state associated
with that behavior persists in
humans.
Natural Selection: Primary mechanism producing evolution
(change over time). There are other mechanisms such as:
sexual selection, social selection, drift.
Basic principles of NS:
1.
Variability: stuff varies
2.
Heritability: variation is passed on genetically
3.
Competition: limited resources
4.
Selection: some variations are advantageous in securing
limited resources and tend to passed on more than others
= change over time
Spencer’s misleading summary of NS: “survival of the fittest.”
After Darwin. E. O. Wilson (still with us)
published Sociobiology (1975) arguing for the
use of evo theory in explaining human social
behavior. William Hamilton (1936-2000)
made the case for inclusive fitness, a gene’s
eye view of evolution which has proved useful
in explaining human cooperation, morality,
tribalism, love, aggression and other social
behaviors.
Eugenics: Evolution and the ‘improvement’ of the human race
• In Victorian England views that today would be considered racist and sexist were fairly commonplace.
“Civilized” Europeans (especially the English) saw themselves as superior to ‘savage races,’ and men were
often considered more intelligent than women. For many, natural selection provided scientific legitimacy to
these views and Spencer’s idea of ‘progressive evolution’ was seen as part of the natural order of things.
Hence, allowing ‘inferiors’ to reproduce at rate greater than ‘superiors’ was seen as unnatural and
threatening to continued social progress. Eugenics was the idea that society should actively encourage
‘better’ people to reproduce while discouraging ‘inferiors’ from doing so. Even though Darwin did not see
evolution as producing inevitable progress, he was not immune from the general zeitgeist of the times.
Francis Galton (1822-1911). Argued
that intelligence was largely a function
of sensory acuity – the speed and
accuracy with which the sense organs
processed inputs – and sensory acuity
was determined by inheritance. Thus,
intelligence is inherited. While he did
develop sensory acuity measures (rt to
visual and auditory signals, highest
perceivable pitch, etc.), he was more
well-know (with regard to intelligence
studies) for his studies of eminence.
Galton studies families of eminence (politicians, wealthy
businessmen, scientists, military commanders, etc. to see if
their offspring were more socially, economically successful
than the general population. They were. Since eminence ran
in families, he argued this supported the hypothesis that
intelligence was largely inherited. He did note, however,
that intelligence must be combined with
‘zeal and vigor’ for success.
Rise of Nature – Nurture debate
• Partly in response to Eugenics, French botonist Alphonse de Candolle
(1806-1893), argued that environmental factors such as education, climate,
economic prosperity, etc. were critical in the creation of scientists.
In response Galton developed a questionnaire (first use of the research
method) distributed to English scientists (members of Royal Society) asking
about a wide range of issues including physical traits, political views,
religious beliefs, educational background, family, was their scientific interest
innate, etc. Most thought their scientific interest was inherited. Galton also
undertook twin studies (first use of the method) finding that identical twins
were more similar to one another even when reared apart compared to
fraternal twins rear together.
Galton’s many contributions to psychology: along with questionnaires and twin studies, Galton initiated studies in
mental imagery (normally distributed in population, however many highly intelligent people including scientists, were
very poor at imagery. Correlational studies: provided some of the first evidence of the co-variation of quantifiable
factors. He did this visually using scatterplots. Karl Pearson (1857-1936) later developed the r stat. Galton also noted the
regression toward the mean phenomenon (tall people had tall offspring – inheritance, but not quite as tall as they and
vice-versa with short people). First word-association tests, later used extensively both by Freud and in memory research.
Championed idiographic approach to studying humans, that is extensive measures for identifying individual differences.
Idiographic Testing in America
• Galton’s method of extensive individual measurement was brought to American by
James Cattell (1860-1944), a student of Wundt and research colleague of Galton.
Cattell developed a series of ‘mental tests’
that he believed measured intelligence. An
intensive set of 50 test were designed to
be used to assess incoming university
students, while a more restricted set of 10
could be used on the general public.
In 1901 Clark Wissler, then a grad
student under Cattell, found no
significant inter-correlations among
the ‘mental tests’ and no relationship
among the tests and academic
performance. Results thoroughly
contradicted Cattell’s assumption that
the tests measured intelligence.
Cattell’s 10 tests
I. Dynamometer Pressure (hand squeeze)
II. Rate of Movement. (quickest possible movement
of the right hand and arm from rest through 50 cm.
III. Sensation-areas. (two-point thresholds)
IV. Pressure causing Pain. (pressure applied by a tip
of hard rubber 5 mm)
V. Least Noticeable difference in Weight.
VI. Reaction-time for Sound.
VII. Time for naming Colours.
VIII. Bi-section of a 50 cm. Line
IX. Judgment of 10 seconds time. (I strike on the
table with the end of a pencil and again after 10
seconds, and let the experimentee in turn strike
when he judges an equal interval to have elapsed.)
X. Number of Letters remembered on once Hearing.
History of IQ testing
• The origin of IQ testing can be found in Galtonian emphasis on individual differences in intelligence.
In France, this initially took the form of the development of an assessment measure that would
reliably distinguish between ‘normal’ (now called ‘typically developing’) children and ‘mentally
retarded’ (now called ‘developmentally disabled’ or ‘atypically developing’) children. The person
heading this effort was Alfred Binet (1857-1911).
Binet’s original test was largely successful at identifying
children with mental developmental delays. Quickly,
however, the goal shifted to assessing differences
intelligence levels of typically developing children. For
this, Binet and Theodore Simon constructed a test that
use chronological age as the referent. Measures were
developed that at 75% of children of a certain age could
pass. This was considered ‘age appropriate.’ Children
were given measures appropriate for their age, if they
passed they were then given tests for the next higher
age level. If they failed, they were given the test for the
next lower age level. Eventually, the Binet-Simon Scale
of Intelligence included 5 age appropriate tests for 3-15
year-olds. Thus children’s mental age could be assessed
per year in five increments. Ex. Someone passing all the
tests for a 7 year-old and 2 tests for an 8-year-old had a
mental age of 7 and 2/5ths.
It was German psychologist
William Stern (1871-1938)
who proposed the original
IQ formula. Louis Terman
later added the ‘x 100’ part
to remove the decimal
place. Simple
interpretation >100 below
normal; <100 above
Charles Spearman and ‘g’
• Charles Spearman (1863-1945). Student of
both Wundt and Kulpe. Found that
measures of sensory acuity (speed and
accuracy of sensory responses) were highly
inter-correlated and correlated with school
performance. Developed factor analysis to
study correlational patterns.
Cyril Burt (1883-1971). Twin studies seem to support
inheritance of g. Correlationed IQ scores among identical
twins higher whether reared together or apart compared to
non-identical twins. Later accused of fraud, but studies largely
replicated.
Argued that the results of these studies indicated
two components to intelligence: specific abilities
(s) upon which people varied (mathematical
ability, memory, language, etc.) and general
intelligence (g). (g) was more fundamental (s’s
arose from g) and (g) was largely inherited and
relatively fixed. On this point, he clashed with
Binet, who argued that while some aspects of
intelligence were inherited, most people
functioned below their native ability and mental
orthopedics (training in focusing attention,
developing study skills, logical reasoning, etc.)
could actualize inherited potential.
Deteriorating National Intelligence?
• If intelligence was largely inherited and less intelligent people were both (a) reproducing more, and (b)
immigrating in larger numbers to the US, then could deteriorating national intelligence represent a threat to
American society? The question became a great concern for both political leaders and some scientists.
Concerns over deteriorating national
intelligence were heightened when
psychologist Henry Goddard (1866-1957)
administered a translated version of the
Binet-Simon scale to over 2,000 New Jersey
public school students and found an
alarming number of them were below age
norms. This prompted him to further
investigate the connection of heredity and
intelligence in his famous “Kallikak” family
study.
Goddard found that the
descendants of Martin Kallikak
from his liaison with a ‘feebleminded’ barmaid were far more
likely to be thieves, prostitutes,
convicts, alcoholics and every
other sort of miscreant, while the
descendants of his later marriage
to a ‘worthy girl’ were more likely
to be socially successful doctors,
lawyers, etc. This was taken as
evidence of hereditary ‘feeblemindedness which was thought
at the time to be behind many
forms of social vice, immorality
and criminality.
Lewis Terman and the Standford-Binet
• Lewis Terman (1877-1956). Responsible for revising the Binet-Simon scale for an American population, called
the Stanford-Binet Test of Intelligence. As was common at the time, he held a largely nativistic view of
intelligence. Validated the Stanford-Binet by correlating it with academic performance (those you did well on
S-B were found to also do well in school). Also well-known for his studies of gifted children (defined as IQ
135 or greater).
Leta Stetter Hollingworth (1886-1939). Studied at Columbia University under
E. L. Thorndike and influenced his views on intelligence from nativistic (women
are generally less intelligent than men) to more nurture (limited opportunities
often give the impression of less intelligence in women in general). Argued that
simply labeling a child gifted did little to actualize potential. Often gifted kids
are bored and thought ‘troublesome’ by teachers. Specific tasks necessary to
challenge are necessary to kept gifted kids engaged.
Terman’s ‘termites.’ Studied over
1,000 gifted children for nearly 80
years. Contrary to widely held
beliefs at the time, Terman found
that intellectually gifted children
were largely well-adjusted and
successful social and especially
economically throughout life. By and
large, gifted children tended to
become gifted adults.
Group Aptitude Tests
• At the outbreak of WW1, the Army was faced with
an influx of new recruits and needed some way of
assessing their mental acuity. Robert Yerkes (18761956), headed a project designed to create a largescale group administered intelligence test. The
result was the Army Alpha (for literate test-takers)
and Beta (non-literate and non-English-speakers).
The test were based on a simple ‘point score’
system where a total intelligence score was
produced rather than a mental age assessment.
Most group administered academic tests (ACT, SAT,
GRE, etc.) can trace their origins to Yerkes efforts.
For his efforts, Yerkes
was made a Major in
the Army. Examples of
parts of the Alpha and
Beta (right)
David Wechsler and Modern IQ testing
• David Wechsler (1896-1981) developed the
most popular IQ test being used today. He
created separate tests for different age
groups (WAIS, WISC, WPPSI). His scales were
normed with standard mean and deviation
score. This creates a total score and
percentile rank.