Measuring the mind: what are Galton's thoughts about individual differences? - Chapter 7

London's International Health Exhibition of 1884 was characterized by a remarkable exhibition called the anthropometric laboratory that drew many spectators. These spectators became test subjects in this laboratory and eventually received some comparative information about themselves. The devices in it laboratory tested the test subjects different ways and gave them their score and the average score of the previous test subjects.

At that time, these tests were seen as mental tests to measure aspects of intelligence. Today, we see that intelligence uses "higher" mental processes, such as thinking, reasoning and logic. Nevertheless, the creator of these tests, Francis Galton, argued that the people with the highest intellectual possibilities, logically also had the most powerful and most efficient nervous systems and brains. He thought that the powers of one's brain was possibly in relation to its size. So the first test to measure the supposed intelligence of a person was to measure size of one’s head.

He also thought that someone's neurological effectiveness should be related to the speed in which this person can respond to something, therefore there was also a test of response time. He believed in two incorrect, but then generally accepted prejudices, which according to him proved a major correlation between sensory acuteness and intelligence. The first prejudice was that people with intellectual disabilities have both a sensory and intellectual disability. The second bias stated that women were generally less intelligent than men and that they can perceive things less vividly.

Fechner's psychophysics had studied the limitations of sensory discrimination and the Wundtian mental chronometry experiments had carefully measured the reaction time. But these previous studies only focused on established, general psychological principles that apply to all people, while individual differences in sharpness of mind or response time were avoided or rejected. The founder of the Anthropometric Laboratory assumed a Darwinian framework in which variability and adaptation were included. Individual differences in sharpness and reaction time were not "errors" or "irregularities" that were to be avoided but instead were the basic mechanism of evolution and therefore an important subject of interest. The anthropometric laboratory led to the development of the psychology of individual differences. This is a discipline that focuses on measuring variations between people at certain psychological characteristics.

Francis Galton (1822-1911) was the younger cousin and friend of Charles Darwin. He was a curious person and was discoverer, geographer, meteorologist and a biological researcher before he turned his attention to measuring intelligence and other psychological attributions. Many of his psychological ideas (such as his theory of measuring intelligence) were found to be incorrect and too simple. He was, however, the pioneer who came up with the idea that tests can be used to measure psychological differences between people. In addition, he also delivered provocative theories about the origin of these psychological differences and wrote controversial social policy documents with the aim of improving the positive psychological qualities in the general population.

What did Galton's former life and career look like?

During his medical training at Birmingham hospital, Galton prepared medication and pills in a pharmacy, and could not resist the temptation to try out small quantities of his own creations. He saw this as an interesting experience but using himself as a test person obviously also had disadvantages. Galton attended mathematics classes Cambridge and became interested in the research procedures of the university. He studied graduated from Cambridge in 1844 and went on to study medicine in London. His father died in 1845 and left Galton with a lot of money. Instead of studying further, Galton started hunting and gambling. Eventually, in 1849, he consulted a phrenologist for an analysis (based on the size of his head) of his "natural" abilities, skills and preferences. The answer he got was one Galton liked, because now he could ascribe his mediocre academic achievements to the lack of innate scientific ability, rather than to his lack of effort and perseverance.

After discovering a part of southwest Africa (now Namibia), he found out that he did have a talent for performing precise measurements. He noticed this when he was on an expedition and used a heliostat, sextant and other surveying instruments for making a very detailed and accurate map of the country. For his detailed map and geographical measurements of the country, Galton won the Royal Geographical Society's gold medal in 1853, the same year that he published the book 'Tropical South Africa'. His successful expedition gave him access to the Executive Councils of the Geographical Society. In the next ten years, he kept himself productively engaged in geography, travel and meteorology. This is how he developed, among other things, a new and improved instrument for geographic measurements and wrote a manual in 1855 for travellers in the wilderness, 'The Art of Travel'. In 1860, Galton developed the world's first weather maps. He discovered the patterns of high- and low-pressure areas. For this alone, he earned a place among the Victorian researchers. But in the beginning of 1860 the 'Origin of Species' shifted his attention in yet another direction.

What was Darwin's influence on Galton?

Galton initially had mixed feelings about Darwin's book, mainly because of his large orthodox faith and trust in the Bible, which were turned upside down by the Origin. Because of this, he suffered of an emotional dip for a few years. Later, however, he used Darwin's ideas for his own theory. Although Darwin did not describe mankind in his 'Origin of Species' Galton quickly understood the implication of this theory, that people, like other species, are also in constant need to evolve. He also believed that the most distinctive human variations, those of which most likely to form the basis of future evolution and development, are by nature intellectual and psychological. Presumably, however, these are mediated by only small hereditary differences in the structure of the brain and the nervous system. 

Galton’s personal experiences even made him believe that individual differences in intelligence are mainly innate. After reading Darwin's book, Galton decided to use his love of measurement and counting to approach this problem statistically. He investigated the biographical dictionaries and calculated that people who were important enough to be called in these books represented a proportion of 1 in 4,000 in the normal population. He also studied family trees  of the families of these people and found that ten percent also did have a relative who was mentioned in a biographical dictionary as well. Here was a concrete one empirical evidence of the statistical tendency for excellence in families. 

Galton acknowledged that this evidence alone did not prove that excellence was hereditary, because family members share, in addition to heredity, often the same environment. This hereditary environment question still lives today. Yet Galton was interested in the heredity of this story and presented his findings in the book 'Hereditary Genius' in 1869, in which he claimed that the natural skills of man are derived from heredity, with exactly the same limitations as the shape and physical properties of the whole organic world. This book provided three new arguments to support this claim, based on the normal distribution of intellectual qualities, the specific patterns of excellence that Galton observed the most, and the comparison of adoptive versus biological family members.

The first argument, the normal distribution. Galton stated that the measurements of intellectual skill tended to fall into statistical distributions in the same way as inherited physical properties. The Belgian statistician Adolphe Quetelet (1796-1874) had previously already shown that measurements obtained from large populations, for example of height or weight, could often be placed in a bell-shaped, normal distribution. Today it is known that the normal distribution also can take shape with countless variables that are not inherited. Galton's observations were mainly consistent with his statement, without providing positive evidence.

Galton's second argument had a similar limitation. He examined the family trees of twelve groups of excellent people and found two general patterns. First, the outstanding family members of outstanding people tend to be closely related to each other: first-degree relationships (brothers and sisters or parent-child) occurred four times more often than third-degree relationships (great-grandparents, cousins, etc.). Even third-degree relationships were more common than would be expected based on chance. This same pattern was found with physical properties. For example, fathers and sons are more similar in length than grandfathers and grandsons. Secondly, Galton found an imperfect but clear predisposition among family members to excel in the same areas. Every descendant of an excellent parent will then have a proportion of the required qualities for excellence in that area but will not necessarily make a move to become excellent. However, it is important to keep in mind that close family members often share the same environment to a greater extent than distant relatives.

Galton's third argument: adoptive versus biological family members: which he recognized in 'Hereditary Genius' but minimized. Galton provided the possibility that the environmental benefits within excellent families could have helped produce these results. He assumes that "social advantages are not enough to make a man with moderate skills excellent ". He further proposed a research design that, when correctly implemented, was promising to provide concrete evidence for his claim. This approach concerned the comparative study into adoptive relationships of outstanding people. As a result of his research, Galton concluded that social and environmental benefits are less important than heredity in the cause of excellence. Galton's idea of ​​comparing adoptive versus biological relatives were so good that generations later it became a technique that genetic researchers applied. Nevertheless, he did not apply the same statistical care to this analysis, and also limited his study to a small and unusual sample of questionable general representativeness.

What is the role of nature and nurture?

The Swiss botanist Alphonse de Candolle (1806-1893) reacted critically to 'Hereditary Genius'. In contrast to Galton, he was primarily interested in the importance of the environment and cultural factors in maintaining success within families. To test this vision, de Candolle collected biographical information of more than 300 major European researchers, which he statistically analysed in his book 'History of the Sciences and Scientist over Two Centuries' in 1873. In it, he admitted that heredity plays a certain role in causing scientific excellence, but he also clearly showed that outstanding researchers mainly came from small to medium-sized cities with temperate climates, democratic governments, tolerant religious institutions and thriving commercial interests.

De Candolle’s book encouraged Galton to carry out his further research on scientists to extend and to investigate the effects of heredity and environment in the background of these scientists. He came up with an extensive questionnaire in which personal information was asked. This marked the first self-questionnaire method. After reviewing the completed questionnaires, Galton concluded that most scientists were born with the requirement preferences and abilities for their profession. Therefore, according to him, the most important causes are hereditary. But some other responses led to Galton having to do an important concession to de Candolle. Many scientists got experiences or influences that presumably strengthened their scientific preferences. This seemed evidence for an environmental influence, which caused Galton to moderate his heredity theory slightly, where he insisted that the hereditary side and abilities were necessary, but not sufficient to cause excellent scientific talent. So there was a support for this needed from the environment.

Galton adopted the slogan: nature versus nurture. Nature (predisposition) is what a person gets with his birth and nurture are all factors that affect him or her after his birth. This slogan he used in 1874 in his book 'English Men of Science: Their Nature and Nurture'. In it, he acknowledged that both the nature and the nurture side had affected the lives and careers of his subjects. He also saw that nature and nurture often interacted with each other in a complex way. To investigate this, he devised the twins research. This is a research technique that he uses 1875 introduced under the name "The History of Twins, as a Criterion of the Relative Powers of Nature and Nurture ".

There are two types of twins, the first of which are two-person twins (dizygotic) that share 50% of their genes. The second kind are identical twins (homozygous), which are genetically completely equal. Galton found that a significant amount of his results from the research, the twins fell into two general categories. Some showed strong similarities, both psychologically and physiologically, despite being confronted with very different life events. Others grew to be completely different individuals, while they were treated the same by their parents. So he concluded, although he had no information about the biological type of the twins, that these results to be expected when one assumes physical and character traits that are particular are determined by genetics, rather than environment. Homozygous twins will therefore end the same way, despite the difference in nature, and dizygotic twins will have differences, just as ordinary brothers and sisters, despite being treated the same (i.e. the same environment). With this Galton introduced an ingenious but not yet convincing approach to the complicated problem naturally versus nurture.

What was the eugenic society?

Galton thought up the term eugenics for his project, in which he could improve the human race by 'breeding' selective characteristics. He believed in the fact that human competence was actually hereditary. Almost everything he did from that moment on was all about eugenics. Two of his most important developments are intelligence tests and statistical correlation.

To create a eugenic society, all men and women with the best possible characteristics had to produce children. But how did you know at a young age who was and was not a ‘good’ fit? In 1884 he founded the Anthropometric Laboratory for London's International Health Exhibition. Here he tried to measure the hereditary intelligence of people by a number of simple tests, such as measuring head size, reaction time and sensory acuity. However, high scores were found not to correlate with reality. The first successful intelligence test was developed by French psychologist Alfred Binet, his test was based on completely different assumptions than Galton's. The idea of ​​an intelligence test in a eugenic environment did, however, come from Galton.

Heredity and eugenics led to another important innovation when Galton developed these relationships from a mathematical point of view. Heredity concerns variables that tend to interact with each other, but do not do that in a perfect way. For example, tall fathers have tall sons, but often not of exactly the same length.  From the results he found, he developed a kind of scatter plot.  In this type of scatter plot, he saw a regression towards the average (regression toward the mean): extreme scores on one variable tend to be associated with scores closer to the average on another variable. See page 261 for further explanation.

Galton discovered even more, namely the regression line: when the averages of each column are represented by X's in a graph, they tend to form a series that create an almost straight line. Galton saw that the slope of each regression line differed, depending on how strong the relationship between the two variables was. In addition, the values ​​of this line were always between 0.0 and 1.0.

In 1888, he discovered that when all scores were converted into standard scores (such as the standard deviation, or the standard error), that before these regression lines were drawn, the mathematical slopes of these lines could be interpreted as the correlation coefficient. These are numerically accurate indexes of the strength of the relationship. When the value is close to 1, like for example 0.8, it indicates a strong relationship. Galton presented all these ideas in 1888 in his paper "Co-relations and Their Measurement, Chiefly from Anthropometric Data ". The brilliant young mathematician Karl Pearson (1857-1936) went with these ideas as a starting point and improved them, with which he developed a simple formula to calculate the "product moment" of correlation coefficients and also expand the range to also to be able to observe the negative relationships. This is also called the Pearson's r. So In the calculation of the Pearson's r, it appeared that the correlation between the test scores from the study of Galton and the actual scores to be very low.

What are other contributions from Galton?

Galton was one of the first serious fingerprint researchers, which he hoped would have a hereditary basis. For this he developed a method to classify prints into 'loops', 'bows' and 'spirals'. In addition, he also devised questionnaires for individuals to investigate differences in mental imagery. He discovered that some literally "saw" the images in their heads, while others only had abstract "thoughts". People therefore differed greatly in the frequency, intensity and liveliness with which they imagined something.

Galton came up with the word association experiment. It meant that 75 stimulus words were put on pieces paper, after which they are put into a random order, and man had to retrieve and say  the first two or three thoughts that came into mind after seeing each stimulus. Galton discovered that these are often associations from childhood. Galton never persevered and continued this research, but Sigmund Freud did. Galton also developed "composite portraits" of different faces, a "beauty card" of the best-looking residents of the British Isles (the most beautiful inhabitants appeared to be from London) and he started up an investigation of the effects of flu on the imagination. He tried to do unsuccessful mathematics with only use the sensation of smell and experimented with different techniques for it making tea. Galton also claimed to have discovered that many intellectuals and scientists in particular, very much weak visual capacity, and that sometimes they are totally lacking.

What is Galton’s influence?

Twin studies, self-report questionnaires, correlational studies and research into mental images and word associations are still present, just like intelligence tests. Despite that Galton was very influential, the nature-nurture debate continues to exist. Even though everyone agrees that both factors are significant. Race is also still a confusing, bitter issue. Galton has contributed to this, because his writing sometimes expressed racism. Another controversy is how eugenic ideas can be applied. Galton wanted to use it in a positive way, but it was also used in a negative way around 1900, such as a strict immigration policy and racial purification. Years after Galton's death, a number of his ideas were submitted by Nazi Germany adopted to promote the Holocaust.

In 1920, it was discovered that with research into separate identical twins, an almost perfect indication of heredity can be found for each trait, including IQ, provided to two important conditions are met. The first is that twins must be demonstrably homozygous and thus have an identical genetic structure. The second and more problematic condition is that they must actually have been separated in their former childhood and randomly placed in a representative selection of adoptive families. Only when these conditions are fully met, and the IQs of the twins is measured in adulthood, the correlation between their IQs can actually be an exact measurement of the heredity of this characteristic. The first major investigation into "divorced" twins was in 1937 by the Horatio team Newman (1875-1957), Frank N. Freeman (1880-1961) and Karl Holzinger (1893-1954). She found that the correlation between the pairs of twins and their IQ .67 was strongly positive, but definitely not absolute. They did find personal stories in which twins found each other again after years and then it turned out that they had had very similar academic careers and IQs. In another example where the twins ended up in two different environments, however, their IQs differed by 20 points. From these studies it appears that there really is an environmental effect is present.

Who are Burt and Jensen?

In 1960 an exception to these results was found by the British psychologist Sir Cyril Burt (1883-1971). He stated that the intelligence tests correlate by about .80, which means that there is a very strong effect is by nature, compared to nurture. The article that he wrote about this impressed the American psychologist Arthur Jensen (1923-2012). During the late 1960s, Jensen studied the Effectiveness of Operation Head Start, training programs for city children from bad environments. This did not work. He used this when interpreting his results from Burt. These findings suggest a greater influence of heredity than environment. Leon Kamin was asked by his students to read and check the articles of both men check for statistical analysis. Burt's article proved to be seriously inadequate, IQ tests were not mentioned by name, meaning that no information was given about the composition of the sample or the times that he had tested his hypothesis for error. Many crucial details from Burt's articles have never actually been published. According to Kamin, the work Burt did cannot be taken seriously. Kamin even thought that it could be entirely possible that heredity does not even play a role when it comes to intelligence. In 1998, Jensen, however, published his book ‘The g factor’, as if he were the first to question the data Burt had produced.

The largest and most impressive post-Burt study on divorced twins is the Minnesota Study of Twins Reared Apart, also called MISTRA. Their conclusion is that nature has a larger share in intelligence than nurture does in common middle class, industrialized societies. It is clear, however, that if all the surrounding types, including poor and disadvantaged households, were included in the study, the heritability estimate would be much lower. The weight that becomes assigned to nature or nurture is thus dependent on the reference group in which the researcher interested.

ExamTips

• If you find the eugenic society hard to understand, delve into genetics a little and then especially the genes and alleles. It will help you, I promise.
• If you understand, ask yourself, why are twin studies so important to psychology? What can it offer us that normal family relations can't?