From Schacter (2023)
A Working Definition Of Intelligence
Intelligence is the ability to direct one's thinking, adapt to one's circumstances, and learn from one's experiences. In other words, intelligence is the ability to use one's mind to solve novel problems and grow from that experience.
From an evolutionary biology point of view, it is better to think of intelligence as an ecological niche, like the skin of a chameleon.
Genetic Basis of Human Intelligence
And that is the point where we need to examine new information about the gene hTKTL1. The modern human variant of the protein
TKTL1 (hTKTL1) during fetal brain development compared to the archaic variant found in Neanderthals and Denisovans as well as apes. One amino acid--arginine--replaces the more archaic lysine and modern humans are created. Anneline Pinson, (2022).
This effect is primarily characterized by:
Increased Progenitor Abundance: hTKTL1 specifically increases the abundance of basal radial glia (bRG), a type of neural progenitor cell that is exceptionally efficient at producing neurons.
Frontal Lobe Expansion: Because hTKTL1 activity is highest in the frontal lobe of the fetal brain, it is believed to have led to a greater production of neurons in this specific region, potentially contributing to modern human cognitive abilities.
Late-Born Neurons: The increase in bRG leads to a higher production of upper-layer neurons, which are generated later in development and are crucial for complex brain circuitry.
Metabolic Mechanism: The protein achieves this by stimulating the pentose phosphate pathway and increasing fatty acid synthesis, which provides the lipids necessary for bRG cells to grow their long processes and continue proliferating.
Research published in Science by Pinson et al. used CRISPR-Cas9 to "Neanderthalize" human cerebral organoids, demonstrating that replacing the modern human arginine with the archaic lysine reduced both bRG and neuron production.
Why is a creating a simple 'working definition' of intelligence so difficult? One of the reasons is anthropocentrism, the projection of human abilities onto non-human organisms. If they don't have human qualities, such as auditory language, we don't perceive them as intelligent.
So what do we make of brainy bees?
https://www.pnas.org/doi/abs/10.1073/pnas.1202576109
Intelligence is a process (or a set of processes) not a single thing. There is a common mistake called reification, or making intelligence a single object. During this chapter, reification will play itself out as the argument over the existence of a general or
'g' factor of intelligence.
Measuring Intelligence
How do we measure intelligence? The worst misuse of measurement occurred in the 1920s on Ellis Island, when Henry Goddard administered intelligence tests to Jews, Hungarians, Italians, and Russians. He concluded that they were 'feeble-minded' That's because the test was in collegiate English. The U.S. subsequently passed laws restricting the immigration of people from Southern and Eastern Europe, and 27 states passed laws requiring the sterilization of 'mental defectives'.
Canada is not exempt from this kind of misuse of science. Sterilization laws for mental defectives were passed in British Columbia and Alberta in the 1920's and not taken off the books until 1972.
Intelligence tests were originally developed when France made primary school education available to every class, and suddenly French classrooms were filled with children who differed dramatically in their ability to learn. Poor children had come with their parents from the French countryside, looking for jobs in factories, and they moved into the suburbs of Paris (which are still filled with poor immigrants.)
Binet developed tests for an intelligence quotient, or I.Q.
Binet's goal was to measure what he termed natural intelligence, and his tests did this by creating a test environment by disregarding the degree of instruction the subject already possessed. The subject was given nothing to read, nothing to write, and submit the subject to no test by which he might succeed through rote learning. In short, Binet was measuring aptitude as contrasted to prior educational achievement.
Stern, (1914) quantified Binet's approach and created the Ratio I.Q, which
is a statistic obtained by dividing a person's mental age by the person's physical age and then multiplying the quotient by 100. Used for testing children. Updating the test for adults the Deviation I.Q. is a statistic obtained by dividing a person's test score by the average test score of people in the same age group and then multiplying the quotient by 100. Used for testing adults.
Modern Intelligence Testing: The WAIS
Wechsler Adult Intelligence Scale or WAIS consists of a set of sub-tests for verbal comprehension, perceptual reasoning, working memory and processing speed.
For more go to: https://strategicpsychology.com.au/wais/
To see how well you can understand the WAIS: answer this set of questions:
(1) What are the core subtests for Verbal Comprehension? Give one test example;
(2) What are the core subtests for Perceptual Reasoning? Give one test example.
(3) What are the core subtests for Working Memory? Give one test example.
(4) What are the core subtests for Processing Speed? Give one test example.
That last one is particularly interesting in terms of neuroscience, because research has shown that individuals with greater cognitive abilities display a greater speed of higher-order cognitive processing.
https://link.springer.com/article/10.1007/s42113-018-0021-5
In conclusion, the WAIS is the most widely used intelligence test, and high predictive validity for important life outcomes, such as income. One reason for this is that intelligent people have a variety of traits the promote economic success: they are more patient; better at calculating risk; better at predicting how other people will act and how they should respond.
The main reason, however, is that they get more education (or in the age of the internet, are they simply more educable?). (Deary et al., 2005) A person's I.Q. is a better predictor of the amount of education they will receive than their social class.
(Deary, 2012).
Equality in Smartland
Nikolaev and Salahodjaev (2016) gathered data on intelligence and happiness from citizens in 21 countries. They found a positive correlation between a nation's average IQ and its average happiness. Calculating happiness using the statistical standard deviation (or 'spread' of scores around an average value) they coined the term 'happiness equality'. If two nations have the same average happiness, the smarter nation tends to distribute that happiness more equally among its citizens. To sum up, if many citizens are ecstatically happy, and many are despondent, then the standard deviation is high, and happiness equality is low.
Intelligence Quotient Versus Academic Performance
The correlation between I.Q. and academic performance is roughly 0.5 9 (or modest) across a wide range of people and situations. Schmidt & Hunter (1998) conclude that for hiring employees without previous experience in the job, the most valid measure of future performance and learning is general mental ability. This last term 'g factor' will be discussed in more depth, as it is highly contested.
The ability to delay gratification is also a powerful predictor of life success (Duckworth & Seligman, 2005) but is an aspect of emotional intelligence, which is arguably not the same as 'g factor'.
Are there other reliable measures of intelligence? Yes. Murphy et al., (2003) reported that intelligence people hold the gaze of their conversation partners both when they are speaking and when they are listening, especially so if the judges are women.
What Is Intelligence?
Charles Spearman developed a statistical technique called factor analysis which explains a large number of correlations in terms of a small number of underlying factors. Schacter's text uses the same approach that I do, to understand this technique by defining athleticism as an underlying factor in hockey and softball. Spearman argued that there is a single, general ability called intelligence that enables people to perform a variety of intelligent behaviours. Remember what I said about reification here. For Spearman, if intelligence is a single, general ability there should bea very strong correlation between people's performance on all kinds of tasks.
Spearman had to modify his theory to explain why a child who scored the highest in math did not score the highest in spelling (but still did well). He posited a two-factor theory of intelligence: every task requires a combination of general ability and skills specific to the task.
Louis Thurstone disagreed. Scores on verbal tests might be highly correlated, but comparing scores on perceptual tests to verbal tests indicated a lesser degree of correlation. This 'clustering of correlations' indicated for him that 'g' did not exist. He posited three primary mental abilities: perceptual, verbal, and numerical.
Those three could be operationalized in six areas: word fluency, verbal comprehension, numeric ability, spatial visualization, associative memory, perceptual speed, and reasoning.
A new statistical technique--confirmatory factor analysis--was verified by Carroll in 1993, using a reanalysis of massive amounts of data from more than 130, 000 healthy adults, school children, infants, college students, people with learning disabilities, mental and physical illnesses demonstrates a threelevel hierarchy. Most intelligence test data are best described with general intelligence at the top; specific abilities at the bottom, and a small number of mid-level abilities in the middle.
Intelligence The Data-based Approach
This starts with people's responses on intelligence tests, then looking to see what kind of independent clusters these responses form. Others use a theory-based approach starting with a broad survey of abilities, looking to see which abilities a particular intelligence test measures.
For the data-based approach, patterns of correlations can reveal middle-level abilities. For example, four specific abilities: (a) balancing teacups, (b)swatting flies,(c) understanding Shakespeare, and (d) summing numbers can be thought of as instances of physical coordination (a+b) and academic skill (c+d).
Carroll (1993) concluded that there are eight independent middle level abilities: memory & learning; visual perception; auditory perception; retrieval ability; cognitive speed; processing speed; crystallized intelligence; and fluid intelligence. Fluid intelligence is the ability to see abstract relationships and draw logical inferences; crystallized intelligence is the ability to retain and use knowledge that was acquired through experience.
Raven's Progressive Matrices Test
Your exams test crystallized intelligence; fluid intelligence tests pose novel, abstract problems that are solved under time pressure, such as Raven's Progressive Matrices Test. This type of test is less likely to be culturally biased.
See for yourself: https://classicaliqtest.com/raven-test/
Raven’s Progressive Matrices is a classical non-verbal test used to measure abstract reasoning and fluid intelligence. The test has been developed by John C. Raven since 1936. It consists of 60 visual questions created by logical matrices, the users shall choose the correct answer in 6 or 8 available multiple-choice questions. The questions are made in sequences from easy to difficult to identify the different parts of your liquid (fluid) intelligence.
This is a completely non-linguistic test so it is fair across cultures and thus becomes the world’s most famous and popular test. Over the 86 years since its publication, Raven’s Progressive Matrices has been widely used by psychologists and the test has been accepted as a standard to join some famous organizations such as The Triple Nine Society, The International Society for Philosophical Enquiry,…
The test has clinical and neurological evaluation, educational placement, occupational assessment, adult neurology treatment and aptitude research.This test has been used and trusted by professional psychologists for near 100 years in 151 countries, in particular the United States.
Sternberg's Multiple Intelligences
Sternberg posited that there are three kinds of intelligence, only one of which is measured by standard intelligence tests. His are: analytical intelligence; practical intelligence, and creative intelligence.
Sternberg argued that tests of practical intelligence are actually better than tests of analytical intelligence at predicting a person's job performance. Finally there is ,
discussed in depth in Assignment Six. Here we find alexthymia, difficulty in identifying and describing one's own emotions.
Emotional Intelligence in Detail
John Mayer and Peter Salovey define emotional intelligence as the ability to reason about emotions and to use emotions to enhance reasoning. Areas of focus for emotional intelligence are: knowing 'trigger conditions' for various emotions; identifying, describing and managing emotions; using emotions to improve decision-making; identifying the emotions of others from facial expressions and tones of voice. Emotionally intelligence people use less neural activity when solving emotional problems than do the less emotionally intelligent.
Genetic Influences on Intelligence
Identical twins (monozygotic) versus fraternal (dizygotic) twins allow us to estimate the influence genes have on intelligence. I.Q. of identical twins raised in the same household have a correlation of +0.86 (very high). Identical twins separated at birth have +0.78 (still very high). Identical twins raised apart have more similar I.Q.s than fraternal twins raised together. Bouchard & McGue, (2003) report that unrelated people raised in the same household (one adopted) have a modest +0.26.
Can Genes Define Intelligence?
Heritability coefficient describes the proportion of the difference among people in a given populationthat can be explained by differences in their genes. Much research (eg: Chabris et al., 2012) concludes that 50% in the difference in people's intelligence test scores (within a particular group) is due to genetic differences. Note that this statistic only applies to groups, not individuals. Think tribes.
The heritability coefficient of intelligence among wealthy children is .72, and for poor children .10. (Turkheimer et al., 2003) Why? Poverty may create much more random home environments.The value of the heritability coefficient also depends on the age of the people being measured and is typically larger among adults than among children. When people have identical experiences, the difference in their intelligence must be due to the difference in their genes. This is shared environment, those environmental factors that are experienced by all relevant members of a household. Don't forget that the most important shared environment is the womb (intrauterine); that is the importance of twin studies. Even identical twins can differ in development, given their location in the uterus.
Here is how location affects them:
Nutritional Access: Even though identical twins share the same DNA, their placement relative to the placenta can cause "unequal placental sharing." One twin may have a better connection to the placenta, receiving more blood flow and nutrients, which often leads to discordant growth or different birth weights.
Health Risks (Monochorionic Twins): Because 70% of identical twins share a single placenta (monochorionic), their proximity to each other and shared vascular connections increase the risk of Twin-to-Twin Transfusion Syndrome (TTTS), where one twin receives too much blood and the other too little.
Physical Development: Late in pregnancy, the limited space in the uterus ("fetal crowding") can lead to physical deformations or minor structural differences because one twin may be more compressed than the other.
Delivery Method: The "presentation" (whether they are head-down, breech, or sideways) determines if a vaginal birth is possible. A vaginal delivery is most likely if the first twin (Twin A, closest to the cervix) is in a head-down position. If either twin is sideways (transverse) or the first is breech, a C-section is typically required.
Birth Order: The twin positioned lowest in the uterus is designated "Twin A" and is almost always born first in a vaginal delivery. Research shows that in 90% of cases, twins maintain these relative positions throughout the entire pregnancy.
Absolute intelligence changes over time. For most people intelligence increased between adolescence and middle age and thereafter begins to decline. The sharpest decline occurs in old age, and may be due to a general slowing of the brain's processing speed. (Zimprich & Martin, 2002). Vocabulary decreases the least (crystallized intelligence), abstract material (fluid intelligence) decreases the most.
Ramsden et al. 2011 studied variation of IQ over time in a group of British teenagers, ages 12-20. The researchers used standardized tests of measure IQ twice, about 3 years apart, and they found that teenager's scores were surprisingly variable. Brain structure changed between Time 1 and Time 2 tests in ways that related systematically to changes in IQ. For example, changes in gray matter volume in a region of the left frontal lobe were important for speech production, which is correlated with their verbal subscale score. The implication is that even in adolescence, local brain regions are growing orshrinking over time.
Flynn effect (2012) The actual I.Q. score is 30 points higher than it was a century ago. Flynn posited that technological revolutions have given people more time to solve the kind of abstract problems that intelligence tests include. So, no sense complaining about smartphones and videogame, which are everywhere on the planet. Every time some in Somalia texts a message, their literacy improves.
Individual Difference in Intelligence
If the average I.Q. is 100 and the vast majority of us--68% to be exact--have an I.Q. between 85 and 115, we see a normal curve being generated. Every 15 points below that is intellectually disabled, every 15 points above is intellectually gifted. Myths abound, here is the truth: People with very high intelligences are less prone to mental illnesses.(Didden et al., 2012). Indeed a 15 point decrease in I.Q. at age 20 is associated with a 50% increase risk for hospitalization due to schizophrenia, mood disorder, and alcohol related disorders .(Gale et al.,2010).
However, 95% of gifted children show a sharp disparity between their mathematical and verbal abilities. (Achter, Lubinski & Benbow, 1996). If gifted children seem odd, it may because of their 'rage to master', they spend more time than their less gifted peers in the sheer amount of time they spend in their domain of giftedness. (Ericsson & Charness, 1999).
What About People With An I.Q. below 100?
About 70% of people with I.Q.s below 20 (profound) are male.
Between I.Q. 50 and 35 Two of the common causes are Down's syndrome (caused by the presence of a third copy of chromosome 21).
Fetal Alcohol Syndrome Brain Structures And Functions.
Prenatal alcohol exposure (PAE) causes permanent and widespread alterations to the developing brain, affecting nearly every region except the occipital lobe, which is relatively spared. These changes include:
Overall Brain Size: Children with Fetal Alcohol Syndrome (FAS) consistently have smaller brains (microencephaly) and smaller head sizes (microcephaly) relative to body size.
Corpus Callosum: This is the most common site of malformation. Changes include thinning, shortening, or complete absence (agenesis) of this white matter tract that connects the two hemispheres.
Cerebellum: Often reduced in size, with specific damage to the anterior vermis. This region is critical for motor control and attention.
Basal Ganglia: Significant volume reductions are observed, particularly in the caudate nucleus, which is involved in learning and behavioral inhibition.
Cerebral Cortex: Alcohol exposure can lead to abnormal cortical thickness. In some areas, the cortex may be thicker than normal, possibly indicating a failure of natural synaptic pruning and neuronal maturation.
Hippocampus: This region, essential for memory, is highly vulnerable. Studies have shown reduced hippocampal volume, which correlates with memory deficits.