Chapter 10

The Darwinian Influence

Updated: 4/20/99

Introduction

• Two themes in this chapter
  • Evolution
    • an old theory given fresh impetus by Darwin
    • gave new strength to movement away from idea of human uniqueness
      • i.e., compare to geocentric vs. heliocentric
  • Measurement
    • the logical culmination of the earlier work on individual differences

Charles Darwin and the H.M.S. Beagle

• Darwin was a naturalist, or someone who studies nature
  • We do not have naturalists any more, nature simply has grown too large
  • Instead, we have specialists: botanists, zoologists, mycologists, entomologists, etc., etc.
• Darwin's Life and Work
  • Wealthy, did not need a job
  • Embarked on warship HMS Beagle (1831-36)
    • collected specimens from all over the world
    • Galapagos Islands (off the W. coast of South America) were especially important to him
    • returned to write up his findings
    • Captain Fitz-Roy felt responsible for his role and may have committed suicide because of it
  • Alfred Russel Wallace
    • independently thought up evolutionary theory
    • Lyell arranged for Wallace's and Darwin's papers to be read on same day
  • Origin of the Species (1859)
    • Darwin's short summary of his work
    • sold out in one day
    • changed the world
• Darwin's Theory of Evolution by Natural Selection
  • Fitness
    • organisms capacity for survival
  • Variability
    • Darwin had noted the immense variability within each species
    • Darwin used that variability to explain natural selection
  • Natural Selection
    • animals that survive trials of nature
    • survivors can change make up of their species
• Modern Theory of Evolution
  • Replaces survival with reproduction
  • Accounts for mechanisms of evolution (Darwin did not know about genetics)
• Social Darwinism
  • Wrong-headed application of evolutionary theory to human behavior
  • Attempt to justify and preserve status quo
  • Led to abuses in U.S. immigration policy

Sir Francis Galton

• Life
  • Half cousin to Darwin
  • Extremely intelligent
  • Liked to measure things:
    • female beauty
    • fingerprints
    • weather
  • Studied with Karl Pearson (of the Pearson Product-Moment correlation)
  • Galton was Darwin's half cousin, and like Darwin was interested in functional aspects of behavior. Unlike Darwin, however, Galton's interest lay in measurement. In the zeitgeist of the latter half of the nineteenth century, Galton's interest becomes clear. For example, cartography, then, had just begun to fill in all of the missing details on the map. The same impulse that led him to help map the world while perhaps young led him to map the mind later.

    Galton did not hesitate to attempt to measure anything and everything, from female beauty to fingerprints to weather maps to the sensory abilities of animals. Galton's observations of relationships between variables and his development of the scatterplot led Karl Pearson to develop his concept of correlation. In 1884, Galton set up a laboratory at the London International Health Exhibition. There, he measured nearly 10,000 subjects. Later, he set up a more permanent laboratory at a museum in London. There subjects, each of whom paid for the privilege, could come to be measured and remeasured later if they liked.

    Galton believed that measures of sensory function were predictive of intelligence. So, he measured vision, hearing, and olfaction. More to the point, he invented the word association test and the digit-span test, both of which continue to be used as item types in modern tests of intelligence. In many ways, Galton can be said to be one of the main founders of psychometrics.

Intelligence Testing

• Alfred Binet
  • In 1904, Binet was asked to develop a method of identifying children with lower than normal intelligence. He and Theodosius Simon, his collaborator, then developed a test that emphasized judgment as the basis of intelligence. They criticized Galton's methods as emphasizing sensory acuity, while claiming that mental judgment was the key to intelligence. For them, intelligent thought involved direction, adaptation, and criticism.

    Mental Age and Intelligence Quotient

    Binet believed that children should be classified by their mental age, or their relative intelligence compared to a hypothetically "average" child of the same age. So, a child could be "ahead" or "behind" his age mates in this scheme. Children could be placed in school by mental age instead of chronological age. William Stern, however, suggested that a ratio, the intelligence quotient (IQ), would be more useful in classification of children of different ages. The intelligence quotient was defined as the mental age (MA) divided by the chronological age (CA), multiplied by 100, or:

    IQ = MA/CA x 100

    Stern's formula for IQ is known as ratio IQ today. However, the utility of mental age in measurement has been problematic because it does not successfully match the data. Children make large gains in intelligence early in life, but as they age, mental age changes less and less. Thus, mental age is not well suited to lifespan intellectual comparisons.

• Lewis Terman
  • The Stanford-Binet Intelligence Scales

    Lewis Terman, a psychologist from Stanford University, translated Binet and Simon's test into English, and changed the scoring to a ratio IQ system. Since that time the test that Binet and Simon created has been known as the Stanford-Binet Intelligence Scales (see text Figure 11-2). While the Stanford-Binet is still widely used, the Wechsler series of tests has become even more popular.

• David Wechsler
  • David Wechsler created a series of similar age-based intelligence tests. The current versions are the Wechsler Adult Intelligence Scale--Revised (WAIS-R), the third edition of the Wechsler Intelligence Scale for Children (WISC-III), and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). All use deviation IQs, and are similarly constructed. They each provide a verbal score, a performance score, and an overall score. The first two are based on separate batteries of tests, and the overall score is derived from the first two.
• Reliability and Validity
  • One of the foundations of intelligence testing is that the tests themselves must be reliable. That is the reason for the existence of the various methods of assessing reliability and the great effort to ensure it. To get students to think of the importance of reliability have them think of a yardstick. Then, ask them to imagine that the yardstick changes a little bit every day. Sometimes it gets longer, and sometimes it gets shorter. If you have a yardstick in your class, pick it up and measure the height of a chair (it should be around 17", but that is another lecture). Then, discuss what would happen if tomorrow the yardstick were longer. Make them figure it out, would the chair be taller or shorter? But, what about the chair? Did it shrink or grow? That discrepancy will allow you to discuss the relationship of the measurement to the true score. Finally, discuss a series of measurements of the chair over a long period with the same yardstick. Assume that the yardstick both lengthens and shortens, randomly, over that period. What will the average measured height of the chair be after that period?

    Once students understand the importance of reliability, you can turn to validity. Emphasize that reliability must precede validity. If the measurement cannot be trusted, then you cannot have validity. However, if you have reliability, then you can begin to work on validity. So, what is validity? At its most basic, validity is whether or not the measurement means anything in the real world. For example, some measurements are more valid than others when it comes to predicting the performance of an airplane in flight. Have students pick some measurements which might predict flying success and some which might not (e.g., the color of the flight attendants' uniforms).

    Finally, emphasize that validity is a local concept. One good way to illustrate that is by counterexamples. In graduate school, I heard a story from my fellow students, out on a consultation, about a client who was giving IQ tests to hire people to load heavy sacks into boxcars. They had convinced their client to abandon the use of that test, and instead devised one of their own. Prospective applicants were taken to a room where a number of sacks had been placed near a shelf. The applicants then had to put the sacks on the shelf. Can you guess about how high the shelf was? Validity is local because a test and a task correlate. Loading the sacks in the test situation will correlate with loading the sacks in the field. Similarly, the items on tests like the SAT correlate with the tasks required in college. So, it is more valid to give the SAT to high school seniors applying to college, but not valid to give it to high school seniors learning a trade. In the latter case, other, more valid tests could be devised.

• Mass Testing
  • Army Alpha and Army Beta (Robert M.Yerkes)
    • America's entry into World War I was the stimulus for the development of mass-testing devices
    • The U.S. Army had to grow rapidly to meet the demand of the War
    • Robert M. Yerkes, an animal psychologist, developed the instruments
    • ASVAB (Armed Services Vocational Aptitude Battery) is the modern version
    • The Army Alpha was for literate recruits, the Army Beta was for illiterate recruits
    • First successful mass testing device
• Henry Goddard and Vineland School
  • Goddard was translator of Binet test
  • Coined the word "moron"
  • Kallilaks study
    • studied family of retardates and concluded that intelligence was genetic
• Early Animal Psychology
  • Georges Romanes
    • Inspired by Darwin
    • Wrote Animal Intelligence
    • Methods were non-scientific (anecdotal)
  • C. Lloyd Morgan
    • Reacted to Romanes' methodology
    • Wrote Introduction to Comparative Psychology
    • Developed Morgan's Canon, a modern version of Occam's Razor
  • Animal psychology was a new and original kind of psychology compared to voluntarism and structuralism
     

URLs

• Talk.Origins Archive--index, interm., short, links, graphics
  • The home page of the Usenet group talk.origins which is devoted to exploring the creation--evolution controversy. Page includes a FAQ and an archive. http://www.talkorigins.org/
• Enter Evolution--index, interm., long, links, graphics
  • Covers Darwin and the theory of evolution, includes links to: topics (3), scientists (25), and UC-Berkeley Museum of Paleontology. http://www.ucmp.berkeley.edu/history/evolution.html
• Charles Darwin--book, adv., short, links
  • Links to full text versions of Darwin's Origin of the Species and the Voyage of the Beagle. http://www.literature.org/Works/Charles-Darwin/
• The World of Richard Dawkins--index, adv., long, links, graphics
  • The "unofficial" home page of Richard Dawkins, author of The Selfish Gene, The Blind Watchmaker and other books about evolution and information. Contains numerous links to related information on Dawkins. http://www.spacelab.net/~catalj/
• FAQ on Psychological Tests--text, interm., long
  • From APA, lists and answers commonly asked questions about tests and testing. http://www.apa.org/science/test.html
• ERIC Clearinghouse on Assessment and Evaluation--index, basic, short, links, graphics, search
  • Comprehensive site on testing and assessment, links to many resources in those fields. Buttons link to: search ERIC, test locator, assessment FAQs, and a full text library. Many other links point to related resources. http://ericae.net/
• Buros Institute of Mental Measures--index, basic, short, links
  • The home page of one of the major sources of tests, has links to: test locators, test reviews, fax services, their Mental Measurements Yearbook, Tests in Print, and to other related resources. http://www.unl.edu/buros/
• The Knowns and Unknowns of Intelligence--text, basic, short, links, graphic, search
  • From APA, lists and discusses known and unknown characteristics of intelligence and intelligence tests. http://www.apa.org/releases/intell.html
• Be Careful of How You Define Intelligence--article, basic, short, links, search
  • Robert J. Sternberg discusses cross-cultural differences in intelligence. He concludes, " We can't assume that the cognitive skills we value or label as intelligence are those valued or labeled in another culture." http://www.apa.org/monitor/oct97/define.html
• Definition--text, basic, short, links, graphics
  • A short definition of a psychological test. http://www.sbs.org.uk/sbs/what.htm
• Sir Francis Galton--text, basic, short, links
  • Short biography of Galton, early pioneer in the testing of human abilities. http://userwww.sfsu.edu/~rsauzier/Galton.html
• Alfred Binet--text, basic, short, links
  • Short biography of Binet, the developer of the first intelligence test. http://userwww.sfsu.edu/~rsauzier/Binet.html
• The Philosophy of Intelligence--tutorial, interm., long, links
  • Discusses topics in the history of testing, includes: Binet and global intelligence, Terman's IQ formula and the Stanford-Binet, Spearman's two-factor theory, Thurstone and primary mental abilities, the Wechsler compromise, and others. http://www.psych.ucalgary.ca/CourseNotes/PSYC331/StudyTools/StudentContributions/DRobbins.html
• Where Have All of the Women Gone?--tutorial, interm., long, links
  • Discusses the contributions of three women pioneers to testing: Mary Whiton Calkins, Margaret Floy Washburn, and Christine Ladd-Franklin. http://www.psych.ucalgary.ca/CourseNotes/PSYC331/StudyTools/StudentContributions/harrington.html
• The Structure of Success--article, adv., long, links, graphics
  • First of Richard Lemann's articles (1995) in The Atlantic on the history of ETS (Educational Testing Service). http://www.theatlantic.com/issues/95sep/ets/grtsort1.htm
• The Great Sorting--article, adv., long, links, graphics
  • Second of Richard Lemann's articles (1995) in The Atlantic on the history of the ETS (Educational Testing Service). http://www.theatlantic.com/issues/95sep/ets/grtsort2.htm
• Two Views of the Bell Curve--article, adv., long, links, graphics, search
  • From Contemporary Psychology, two opposing views on the book the Bell Curve (1994), articles are: Breaking the Last Taboo and Soft Science with a Neoconservative Agenda. http://www.apa.org/journals/bell.html
• Robert Sternberg on the Bell Curve--article, interm., long, links
  • Skeptic magazine interview about Sternberg's views on the Bell Curve (1994). http://www.skeptic.com/03.3.fm-sternberg-interview.html
• The Bell Curve Flattened--article, adv., long, links, graphics, search
  • Nicholas Lemann summarizes methodological objections to the Bell Curve (1994). http://www.slate.com/Features/BellCurve/BellCurve.asp
• ASVAB Home Page--NEW, index, basic, short, links, graphics
  • Describes the Armed Services Vocational Aptitude Battery, the test given to prospective recruits to the U. S. armed services. http://www.goarmy.com/asvab/index.htm
• Example of Romanes' Anecdotes--NEW, article, adv., long, links
  • One of Romanes's anecdotes on animal behavior from Animal Intelligence. http://www.pigeon.psy.tufts.edu/psych26/romanes1.htm
• Conwy Lloyd Morgan--NEW, biography, interm., long, links
  • Biography of C. Lloyd Morgan, the "father of experimental animal behavior." http://paradigm.soci.brocku.ca/~lward/BIOS/PAGES/MORGANCL.HTML