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History & Systems of Psychology
Chapter 10 – Darwinism & Mental Testing

History of Evolutionary Theory
First discussed by Plato & Aristotle, not developed because neither believed in it
Early Christian thought emphasized divine creation of fixed & unchanging species
By 18th & 19th centuries theory of evolution more widespread, Erasmus Darwin one of proponents, but theory lacked a mechanism
Lamarck’s inheritance of acquired characteristics proposed one of first mechanisms

Charles Darwin (1809-1882)
Naturalist/scientist, took famous voyage on the Beagle, a ship on a govt-sponsored scientific expedition from 1831-1836
Began as believer in strict creationist account, purpose was to refute evolution
On Galapagos Islands observed variations in species from island to island
Struggle to make sense of findings aided by reading Malthus’ ideas on something like natural selection at the societal level through pressures of war, famine, & disease

Darwin’s Theory in a Nutshell
There is a natural struggle for survival because more offspring are produced than can survive.
This struggle for survival results in survival of the fittest. In other words, natural selection occurs as those with adaptive features survive.
“Fitness” for survival meant only the ability to survive and produce offspring.

Impact of Darwin’s Theory in Psychology
Focus on inheritance, development, and individual differences.
Developmental psychology
Animal & comparative psychology
Behavior genetics
Abnormal psychology
Tests and measurements
Learning & focus on behavior
Evolutionary psychology

Francis Galton (1822-1911)
Brilliant cousin of Darwin, interested in inheritance of human abilities & individual differences
Loved to measure and classify information; after evolutionary theory known, set out to measure & catalogue individual differences in people, gathered info on more than 9000 people
Interest in measurement of intelligence, demonstrated that it is inherited and that people differ in this trait (vs. old idea of “will”)

Galton, cont.
Had need to analyze vast amount of data
Used scatter plots and observed correlations between variables
Contributions to the field of measurement include:
Correlation (Pearson later developed formula)
Use of median and mean

Psychology & the United States
Experimental psychology developed in Germany, evolutionary theory in England
Transfer of experimental psych to US attempted by Titchener, but unsuccessful
19th century US open to new & practical theories more than abstract analysis of the mind
Evolutionary theory & its psychological offspring embraced in US, creating a uniquely American psychology that made US the center of psychological research to this day; influences in psychological testing, functionalism, behaviorism

Development of Intelligence Tests
James Cattell (1860-1944) brought Galton’s testing to the US, but tests deficient
Alfred Binet (1857-1911) – interest in individual differences, measurement of differences in intellectual ability
1905 Binet-Simon scale of intelligence developed to ID mentally deficient children
Trans. To English by Goddard, revised for US use by Lewis Terman at Stanford in 1912; Stanford-Binet in current edition is one of most widely used IQ tests