Chapter 8: Evolution of General Intelligence

1. David Geary Chapter 8:Evolution of General Intelligence

2. Introduction • There are two methods for studying general intelligence (g) in psychology: • Psychometric Tradition- The study of individual differences on paper-and-pencil ability tests, standardized achievement, and IQ tests. It is one of the longest and most successful research endeavors. • Individual differences in IQ tests as well as other measures of g are strong predictors of individual differences in achievement in school, the ability to learn in non-school settings, and productivity at work. • Cognitive Tradition- Involves the study of processes underlying performance on the test of g and tests of more specific cognitive abilities, including working memory and attentional control.

3. Psychometrics and Mental Abilities • Francis Galton (late 1800’s)- Darwin’s half cousin • Francis Galton did a systematic study of hereditary talent, including mental abilities. • Galton was interested in whether intellectual ability ran in families. • Galton (1865) concluded “that hereditary influence is as clearly marked in mental aptitudes as in general intellectual power.”

4. Psychometrics and Mental Abilities • Spearman (1904) administered a series of sensory and perceptual sensitivity and discrimination tasks, like discriminating one musical pitch from another, to elementary students, high school students, and adults. • Teachers and peers also rated the students in-school intelligence and commonsense. Scores on standardized exams in classics, French, English, and Mathematics were also available for high school students. • All scores across scales were positively correlated. • Spearman concluded that all types of intellectual activity have one fundamental function in common, but specific elements of the activity differ.

5. Psychometrics and Mental Abilities • Factor Analysis- Statistical method for clustering sources of variability across mental and other measures. • Thurstone (1938) used the newly developed factor analysis to find that performance on paper-and-pencil ability tests tended to cluster into a set of primary abilities. • Verbal Comprehension • Numerical Facility • Spatial Abilities • Perceptual Speed • Memory • Reasoning • These primary abilities represent core domains of human intellectual competency. • Performance across these measures was correlated.

6. Psychometrics and Mental Abilities • Spearman and Thurstone’s work revealed that human intellectual abilities could be hierarchically organized. General Intelligence Verbal Comprehension Numerical Facility Spatial Abilities Addition Multiplication Division

7. Psychometrics and Mental Abilities • Cattell and Horn- argued that the single general ability proposed by Spearman (1904) should be subdivided into two equally important and distinct abilities • Crystallized intelligence (gC) • Crystallized intelligence is the result of experience, schooling, and acculturation. It refers to over learned skills and knowledge. • Fluid intelligence (gF) • Fluid intelligence represents biologically based ability, such as the ability to acquire skills and knowledge. • Visualization, perceptual speed, and fluency skills

8. Intelligence Tests • Spearman’s early work and work of other experimental psychologists contributed to the work on the development of standardized intelligence tests, such as IQ tests. • Binet and Simon- developed the first practical IQ test. • Goal- develop an objective measure of children’s readiness for school and to determine whether they were mentally delayed and not likely to benefit from schooling. • Result- a battery of tests ranging from simple motor and perceptual tasks to tests of working memory, judgment, and reasoning.

9. IQ Testing • Current IQ tests used: • Stanford-Binet Intelligence Scale • Wechsler Scale • Raven’s Progressive Matrices Test • Performance on IQ scales is highly stable from year to year • Scoring: • Normal, bell curve distribution • Average Score = 100 • Mental Giftedness = 125 or 130 • Mental Retardation = 70 or below

10. Spearman’s law of diminishing returns • For low IQ groups, low performance on one type of test is strongly predictive of low performance on a different type of test. As intelligence increases, the strength of this relation diminishes.

11. Cognitive and Brain Correlates of Intelligence • With the development of computers and conceptual advances, experimental psychologists were able to study processes that contributed to cognitive abilities. • Speed of Scanning visual information held in short term memory • Speed of retrieving basic facts from long term semantic memory • Speed of executing and coordinating the operations involved in analogical and other forms of reasoning

12. Speed of Processing: Reaction Time • Does the speed of executing elementary processes relate to performance of g? • Hunt et al (1975) found that speed of accessing letter names, word names, and other bits of language from long term memory was related to performance on a paper-and-pencil measure of verbal ability. • speed of access score on test

13. Speed of Processing: Reaction Time • Geary and Widaman found that variables representing the speed of executing two basic processes (arithmetic fact retrieval and carrying from one column to the next) were strongly related to performance on paper- and-pencil tests of Thurstone’s numerical facility, but were unrelated to performance on tests of spatial abilities. • The faster individuals execute elementary cognitive processes in specific domains, the higher they score on paper-and-pencil ability tests in these same domains supports hierarchical models of intelligence.

14. Speed of Processing: General Intelligence • Keating and Bobbitt- found that children who had average scores on IQ tests were slower at accessing letter names from long term memory than children with above average IQ. • Jenson- found that faster speed of cognitive processing is related to higher scores on measures of g • Individuals who are consistently fast in executing these processes have the highest scores on IQ tests, even after extensive practice. • Deary, Der, and Ford- administered IQ tests and simple and complex reaction time tasks to a sample of 900 adults from Scotland. • They found a relation between speed and IQ • The relation was stronger for the complex task. The more g at disposal of the individual, the better they perform.

15. Speed of Processing: Mechanisms • Horn (1988) found that speed of processing was related to speed of identifying basic pieces of information or patterns under conditions that require focused attention and speed of making decisions • Jensen (1998) said that speed of making these identifications and decisions might be related to nerve conduction velocity. • Nerve conduction velocity (NCV) is a test of the speed of electrical signals through a nerve. • P.A. Vernon and Mori (1992) found that faster peripheral nerve conduction velocities, like measuring speed of reflexes from wrist to elbow, were associated with higher IQ scores and faster reaction times on cognitive tasks.

16. Speed of Processing:Inspection Time • The methods involved in reaction time tasks necessarily involve a motor component, like pressing response keys • Time needed for motor response is incorporated into the overall reaction time. • Inspection time is not influenced by motor responses.

17. Measuring Inspection Time • Participant is told to focus on X, they are then shown the stimulus for a given amount of time, and asked to determine if left line or right line is shorter by pressing response key. • Researcher is measuring the amount of time the stimulus must be viewed in order to answer correctly. • Short inspection time is associated with high IQ Fixate Stimulus Mask X Time

18. Electrophysiological studies • In electrophysiological studies, individual differences in IQ are related, in part, to individual differences in the sensitivity with which sensory and perceptual systems identify information patterns in the external world and represent them in short term memory. • More intelligent people identify and respond to subtle variations in external information more quickly than less intelligent people. • Inspection time taps into these individual differences.

19. Working Memory • Working memory- the ability to maintain attentional control and prevent irrelevant information from diverting attention from the task at hand. • Research on the relation between performance on laboratory working memory tasks and performance on IQ tests and other measures of g have focused on Cattell’s and Horn’s fluid intelligence, gF. • Performance on measures of fluid intelligence should be strongly associated with individual differences in working memory. • Embertson- conducted one of the few studies that separated working memory capacity and the processes involved in making controlled, explicit inferences. This study suggests that many measures of working memory capacity are actually assessing multiple skills, specifically the ability to hold and manipulate information in working memory, draw inferences about relations among these pieces of information, and then apply these inferences during the act of controlled problem solving.

20. Brain Regions • Bigger brain=higher IQ • A consistent but modest relation has been found between brain size and IQ scores has been found. • Higher fluid intelligence scores: • Larger total brain volume • Larger dorsolateral prefrontal cortex • More white matter in prefrontal cortex • Dorsolateral Prefrontal Cortex • Involved in maintaining the task goal in the mind, guiding the sequencing of the multiple problem-solving steps, and suppressing the potential interfering effects of distractions • It was active when young adults solved reasoning and related working memory problems. These same regions were active when older adults solved the same reasoning problems but older adults did not perform as well because the activation of several task-irrelevant brain regions that were suppressed in younger adults. • Damage to the prefrontal cortex can severely disrupt fluid intelligence but not crystallized intelligence. It also affects the person's ability to use their crystallized knowledge in novel conditions. • Anterior Cingulate Cortex • Activated when goal achievement requires dealing with a novelty or conflict (e.g. choosing between two alternatives)

21. General Fluid Intelligence • General Crystallized Intelligence • Performance Characteristics • Controlled problem solving: Reasoning, inferring, and abstracting • Knowledge Base: • Facts, procedures, and heuristics • CognitiveMechanisms • Working Memory: • Attentional and inhibitory control; speed of processing; and, short-term memory • Long-Term Memory: • Quantity of organization of information and speed of information access • Brain Mechanisms • Dorsolateral prefrontal cortex; anterior cingulate cortex and other attentional systems and neurophysiological processes supporting short-term memory • Brain regions involved in the storage(e.g. , the hippocampus) of evolved or learned information patterns.

22. Intelligent Individuals • More intelligent individuals require less practice to shift the processing demands of a task from the explicit system to the implicit system • High intelligence=more efficient use of the brain systems, less glucose used by neurons • More able to cope with novel, complex, and dynamic circumstances that require problem solving, reasoning, making inferences, forming abstractions, and engaging the explicit system. • Identify and apprehend bits of social and ecological information more easily and quickly than do other people, and their perceptual systems process this information so it is activated in short-term memory more quickly and with greater accuracy than in other people. • Able to represent more information in working memory • Have an enhanced ability to consciously manipulate this information. • gF is associated a strong long-term memory system combined with an interest in seeking novel experiences. The result is the acquisition of a large store of crystallized knowledge over a lifetime. • Know more facts, procedures for problem solving, and more heuristics.

23. Brain Mechanisms of Intelligent Individuals • The same brain systems that underlie working memory should be engaged when people solve items on IQ tests, and these same systems should differ comparing groups of people with higher and lower IQ scores. • High scores on measures of gF are associated with activation of the dorsolateral prefrontal cortex and several brain regions dealing with attentional control, including the anterior cingulate cortex and regions of the parietal cortex. • Intelligent people are more able to inhibit irrelevant information from intruding into conscious awareness. • They have a larger dorsolateral prefrontal cortex and more white matter, or axons, in this brain region. More white matter indicates more neuronal connections within the prefrontal cortex and a prefrontal cortex that is richly integrated with posterior and subcortical brain regions. • The ability to learn over a lifetime is related to gF, personality characteristics that influence the seeking of knowledge, and the brain systems that support the representation and access to information stored in LTM

24. Heredity of Intelligence • Galton (1869)- demonstrated that accomplishments in politics, literature, science, music, poetry, etc often run in families • concluded that the traits that result in exceptional talent or "genius", are largely hereditary. • Behavior genetic study of individual differences in behavior, personality, and cognition focuses on both hereditary and environmental influences. • As environmental conditions vary within the population of interest, the potential for environmental influences on the trait will necessarily increase. • Environments can influence gene expression, and individuals with different genotypes sometimes seek different environments.

25. Heredity of Intelligence • Bouchard and McGue- closely related family members were more similar in their IQ scores than were distantly related family members. • Results indicate that about 50% of the individual differences in intelligence were related to genetic influences. • Genetic influences on intelligence are moderate during the preschool years and increase in importance as the individual moves into adulthood. • During early childhood, parents provide many of the environmental influences. As individuals mature, they are better able to seek and benefit from experiences such as continued formal and informal educational experiences that can result in improvements in performance on some subscales on some IQ tests.

26. Heredity of Intelligence • DeFries et al (1979)- parents and their biological children resembled one another for several specific cognitive abilities, especially language-related and spatial abilities. • Plomin et al- In a 16 year study of similarity between adopted children and their adoptive parents found that as children matured, they became increasingly similar to their biological parents and less similar to their adoptive parents for measures of g and for measures of verbal abilities, spatial abilities, and short-term memory. • The correlation between performance on IQ tests and measures of specific cognitive abilities appeared to be related to shared genes. There is substantial overlap between the genetic influences on g and the genetic influences for specific cognitive abilities. • There is also evidence for unique genetic influences on competencies in the areas of language, spatial cognition, and short term memory.

27. Heredity of Intelligence 100 Unique Environment 80Shared Environment 60 40 Genes 20 0 Preschool Old Age Developmental Change

28. Heredity of Intelligence • Pederson et al (1992) found the same pattern for a sample of older adult twins and reported higher heritability estimates for some language and spatial measures than is typically found in younger samples, suggesting that genetic influences on specific cognitive abilities might show the same developmental increase found with measures of g. • Petrill (2002) - Intra-individual differences in specific abilities appear to be largely due to unique environmental influences once the influence of g is controlled. • The genetic influences that result in faster speed of processing, quicker inspection times, and greater consistency in speed of processing are the same genetic influences that contribute to high measured intelligence, especially fluid intelligence. • The relation between working memory and fluid intelligence is mediated, in part, by a set of genes that are related to performance on both types of measures.

29. Heredity of Intelligence • Baare' and his colleagues used imaging techniques to determine the overall brain volume and corresponding volumes of gray(neurons) and white(axons) matter for twins and sibling young adults. • Genetic influences explained 90% of the individual differences in total brain volume and 82% and 87% of the individual differences in volume of gray and white matter, respectively. • The remaining differences were due to unique environmental effects; there were no significant shared environmental effects. • P. Thompson et al (2001)- constructed three-dimensional maps of the entire brain for sets of monozygotic and dizygotic twins and were able to estimate the degree of anatomical similarity of the entire cortex for these twin pairs. • In monozygotic twins, Broca's area and Wernicke's areas, which are both associated with language functions; the parietal-occipital association cortices; and several prefrontal regions, including part of the dorsolateral prefrontal cortex are indistinguishable from one another

30. Environment • The environmental effects are composed of influences shared by family members, such as the wealth of the family, and influences that are unique to each individual. The specific types of experiences that influence such abilities are not well understood. • There are several environments that can effect an individual’s intelligence • Prenatal environment • Family environment • Intervention programs

31. Prenatal environment • Prenatal environment- maternal nutrition or alcohol use may influence the prenatal environment in ways that can affect early brain development and, through this, intelligence. • B.Devlin, Daniels, and Roeder (1997)- estimated that maternal effects including prenatal environment, could account for as much as 20% of the similarity in the IQ scores of pairs of monoxygotic twins and 5% of the similarity among other siblings. • Fetal Alcohol syndrome- Maternal alcohol use during pregnancy is associated with brain malformations and lower IQ scores in their children. • Only a minority of fetuses exposed to alcohol develop FAS, and it is unclear whether prenatal exposure to moderate levels of alcohol and other damaging chemicals have long-term influences on intelligence. • Streissguth et al. found that maternal consumption of three or more drinks per day was associated with an estimated loss of five IQ points., but Greene et al found that it may result in a loss of 2 or less IQ points.

32. Family Environment • Adopted children with intelligent adoptive parents score higher on IQ tests than do adopted children with less intelligent adoptive parents, but the relation strength is small. • Virtual twins are formed when parents adopt a child and have a biological child of about the same age. • These children grow up in the same household with the same parents, go to the same school, and likely have many of the same friends. • The IQ scores of virtual twins, at least in childhood, are moderately related. • Families that provide an intellectually stimulating environment allow all of their children to develop their full intellectual potential. • The beneficial effects of such family contexts are not detected in behavior genetic studies because these studies focus on individual differences, and in optimal environments individual differences are more strongly related to genetic variability than to variability across families. • The strongest environmental influences on individual differences in general intelligence are experiences unique to each individual. Unique experiences can influence the development and expression of intellectual activities. Openness to experience is a personality trait that influences general intelligence.

33. Early Intervention programs • Many interventions have been developed to improve the cognitive and social competencies of children living in poverty or other difficult circumstances. • Head Start • These types of interventions appear to result in a number of beneficial outcomes, including improved academic functioning. • Many of these interventions are initially associated with modest, and sometimes substantial, improvements in IQ scores, but most of these gains fade with time. • The gain in IQ was highest for the group of children adopted into professional homes and lowest for those adopted into working class homes. • It was also higher for children with a higher pre-adoption IQ. The brighter children gained more from their experience.

34. Invariance-Variance • The evolved function of brain and cognition is to process information patterns and guide associated behavioral responses that have tended to covary with survival and reproduction outcomes during the species' evolutionary history. • These patterns vary along a continuum from invariant to variant. • Invariant patterns- • Basic shape of the human body • Should result in the evolution of modular systems. • Variant patterns can be understood on at least two levels. • 1. within the constraints of modular systems, such as individual differences in body shape. • 2. At a more macro level, as in the behavioral dynamics of predator-prey and social relationships.

35. Modular Systems • The evolved modular systems associated with invariant information patterns, along with learning during the individual's lifetime, can be mapped onto Cattell and Horn's crystallized intelligence. • The ability to learn during a lifetime should be dependent, in part, on the extent to which modular systems are plastic and thus adaptable to novel conditions. • The result is the potential for acquisition of evolutionarily novel competencies, such as reading. • Adapting to novelty and dealing with complex and varied information is the primary condition that Cattell and Horn found to be associated with fluid intelligence, and thus fluid intelligence can be linked to the selection pressures that create novelty and complexity, but at the macro level.

36. Selection Pressures • Three types of selection pressures • Climatic • Refers to the effects of the environment and long term weather patterns impacting a species. • Ecological • Refers to the ability to extract resources from the environment and, at the same time, avoid being extracted by other species • Social • The achievement of ecological dominance shifts selection pressures to social competition. • Group-level competition and dynamics often require sustained attention and other features of executive control.

37. Selection Pressures and evolution of the mind • A combination of ecological and social factors likely contributed to the evolution of the human brain and mind. • Patterns of cooperation and competition among individuals and coalitions of individuals were the most potent of these pressures, at least during more recent human evolutionary history. • 3 selection criteria include: • generating recurrent and somewhat unpredictable patterns of change during the life span • generates conditions that provide a plausible explanation for the evolution of fluid intelligence. Social dynamics generate recurrent and somewhat unpredictable conditions that would favor the evolution of brain and cognitive mechanisms that enable the ability to anticipate these conditions, inhibit heuristic-based responses, and generate novel behavioral solutions. • they favor the evolution of self-awareness • related to the evolution of autonoetic mental models, of which gF is only one component. • they have the potential for generating a within-species co-evolutionary arms race. • explains the rapid expansion in EQ, and presumably gF

38. Mental Models and Fluid Intelligence • The empirical and theoretical research on general intelligence and gF has identified many of the core features that support the use of autonoetic mental models, which evolved as a result of the social and ecological pressures described previously. • Autonoetic mental model- • The individual is able to mentally generate a problem space that includes representation of the "perfect world". In the perfect world, the person is in control of the social, biological, and physical resources that have tended to covary with the survival and reproductive prospects during human evolution. The behavior of others and the flow of resources align with the individual's best interest. • The real world operates differently, but the goal is to generate strategies that will reduce the difference between the real world and the perfect world. • The ability to use these simulations is dependent on working memory, attentional control, and the underlying brain systems. • Geary believes that evolution of gF was due to social and ecological pressures that are independent of the current uses of standardized intelligence tests in modern society. • The evolved function of gF is to cope with change and novelty in social and ecological conditions.

39. Modulariy and Crystallized Intelligence • J.B. Carroll 1993- concluded that most of the psychometric tests that index gC involve language directly or indirectly, cultural knowledge, and spatial and visual abilities. • Legree 1995- found that measures that assessed knowledge of social conventions and social judgments were related to psychometric g, a combination of gF and gC. • Geary believes that the inherent knowledge represented in the modular systems defines one class of crystallized intelligence. The other class of gC is represented by knowledge learned during the individual's lifetime.