Understanding Intelligence: Genes, Behavior, and Heritability

School

University of Toronto**We aren't endorsed by this school

Course

PCL 200

Subject

Psychology

Date

Dec 11, 2024

Pages

Uploaded by SuperSparrow2411

PSY100 Lecture 6: IntelligenceGenes & Behavior:-What is a gene?Unit of heredity transferred from parent to offspringIn humans, 50% of the genetic material is from the sperm and 50% is from the eggBecause genes determine the structure of the nervous system, they also determine its functional output-Genetic Variation:~20 000 – 25 000 different genesEach of these genes may have multiple alternative versions (alleles对偶基因) with different functionsOur differences in alleles lead to differences in proteins, nervous system function and thought + behavior-Genetic Differences within Families:The more similar we are genetically, the more similar we tend to be behaviorally.-Heritability遗传可能性：Traits may vary significantly (phenotypic variation表型变异, VP)This variability in traits may be due to changes in genetic factors(VG) or changes in environmental factors(VE)

Heritability (H2)is the proportion of phenotypic variation explained by genetic factors, such that:-Psychological traits are heritable:Many psychological traits – including personality, intelligence, ideology and even religiosity – are heritablePsychological disorders are also heritable. Apart from genes, environmentand randomness play a role.-Why do traits become common?Certain traits are associated with the production of more offspring (reproductive fitness)In epidemics, disease resistance traits allow people to live longer and reproduce more oftenPhysical features can be attractive to potential mates (sexual selection)Traits will become more common in the population (i.e. they are “selected for”). In turn, genes for these traits will also become more common in the population.-Key Principles:All traits are heritable (often ~50%)No trait is 100% heritable. The environment always explains some behavioral variability (often ~50%)A typical trait is associated with many genetic variants, with each accounting for a very small percentage of behavioral variability (< 1%) (one trait, many genes)Genes can serve many functions (one gene, many traits; termed pleiotropy基因多效性)Genes affect the likelihood of encountering environments and the response to environmentsIntelligence:-What is intelligence?The capacity to acquire + apply knowledge and skills

A conceptual variable (represents an attribute we think exists)Many theories, including generalintelligence (g) theory, Sternberg’s theoryand Gardner’s theoryOverwhelmingly, behavior geneticsuses g theory-g idea: When we look at the performance of different cognitive tests, we see a similar patternWhy do we see + correlations?One possibility is that the tests are related in some wayThese many tests may look like they are measuring many different traits, but they could all be measuring parts of the same traitPut differently: we’re not examining different abilities in each test, but we’re examining different parts of the same abilityTests of ability:Multiple tests share a source of variance.All tests could be driven by a single factor (the G factor).We estimate g through statistics (factor analysis)-General Intelligence (g) Theory:Are ALL cognitive abilities ENTIRELY driven by g?NO; g is not all that mattersCorrelation between g and any cognitive ability is never perfect (i.e. r ≠1)A proportion of the variability in each ability is not explained by g and must be explained by something elseIn addition to g, which drives all abilities, each ability may be driven by its own specific factor (s)Ability X performance= g(shared by all abilities) + s (which is unique to Ability X)-WAIS Testing:

-Barriers in Cognitive testing:Language ability and culture are concernsIQ tests developed for one group may not apply well to anotherTo reduce the influences of language and culture, it is important to use culture-specific tests and non verbal assays (such as Raven’s Matrices)Famously, Wechsler himself (a Romanian immigrant) was mistakenly identified as impaired as a child-Intelligence Quotient (IQ):M = 100, SD = 15; ~68% scores between 1 SD-Sternberg’s Theory of Intelligence:

Criticisms:Practical intelligence is not independent of gDifficult to prove a causal relationship between job performance and practical intelligenceThe suggestion of “creative intelligence” is especially controversial, as most researchers consider creativity and intelligence separately-Gardner’s Eight Intelligences:Criticisms:No specific guidelinesNo testsoTheory is therefore unfalsifiableoWe cannot use it to predict anythingPossibility that these abilities overlap with g has never been assessedoEach of these intelligences may be a ‘composite’ measure of a specific ability + others-Emotional Intelligence:An ability to perceive, understand, facilitate and manage emotionsStrongest early proposal from Goleman (1995)Multiple models and tests since, including the Mayer Salovey-Caruso Emotional Intelligence Test (MSCEIT)MSCEIT – 4 Branches1.perceiving emotion 2.understanding emotion3.facilitating thought with emotion4.managing emotion

Controversial concept; difficult to define and studyTests of emotional intelligence have been modestly correlated with job performance, academic performance and relationship qualityMay have predictive value beyond that offered by personality tests and standard intelligence testsResearch is still relatively new-Intelligence + Info Processing:People who are intelligent ‘think quickly’Reaction time (RT)is negatively correlated with IQSmarter you are, the faster you react (low RT, high IQ)RT is also a predictor of dementia in the elderlyPeople with high IQ show more efficient brain activity during working memory tasks of moderate difficultySmart people filter distractions better and show less overall brain activity during difficult tasks-On the Intelligent Brain:Intelligence is correlated with white matter integrity, brain size, neuron number and cortical thicknessCortical thickness declines with age, and this may contribute to age-related cognitive declineNot all forms of cognition are equally affected by agingDeclines in speed come first, declines in accuracy come laterEducation is associated w/less cognitive decline-IQ as a predictor of success:In Terman’s famous study, children with a high IQ (mean IQ ~ 150) were tracked for 50+ yearsThe children (‘Termites’) went on to be quite successful-IQ and profession:Correlation with profession and the performance within that professionAssociations stronger for “highly complex” challenging jobs (e.g. medical doctors)-"Too Smart For Your Own Good”Measures of intelligence are correlated with leadership performance (including in heads of state)To an extent, higher IQ is good for leadership positions. However, past a certain point (IQ > 120), IQ may be detrimental to perceived leadership ability

Very high IQ scores are associated with lower perceived leadership ability (curvilinear relationship)-Correlates of IQ:Positively correlated with longevity and height/weightNegatively correlated with criminal behavior and divorce rateSurprisingly, IQ is only modestly correlated with income (r = 0.30) and weakly with wealth (0.16)-Heritability of IQ:IQ increases with age:Why does heritability increase?One theory is that a high IQ allows us to enter into specialized environments that will further reinforce IQ (genetic mediation of environmental effect) Also, genes for IQ may take effect later in life (innovation) and become increasingly important over time (amplification)The Genetics of IQ:oThe philosophy of eugenics优生学proposed that trait improvement in the human race could occur through controlled breedingoPolicies based on eugenics during the eugenics movementhad terrible effectsEugenics Movement:o~30 countries had eugenics policies (such as sterilization) in the early to mid 1900s – including the US and CanadaoEugenics was later appropriated by Nazi Germany in the 1940s and associated with mass genocide

-IQ and the Environment:The Flynn Effect (the observed rise over time in standardized intelligence test scores) suggests that the environment matters!Proves that genetics is not favored as an explanation, as the effect has emerged too rapidly (~50 years)Various potential factors: nutrition, changes at home, world complexity, test complexityMany have argued that the Flynn effect has already stopped and may even be reversing. The reasons are unclear; it is possible that a ceiling effect of the environment exists.oBenefits might hit a ceiling (asymptote渐近线). Past this point, increases in environmental quality might not matterGreatly enriched environments do not seem to be beneficialMost treatments (e.g. cognitive training) have failed to produce a lasting increase in cognitive abilityCommercial ‘Brain games’ do not work, despite their popularityParenting strategies generally have weak influencesScarcity Mentality稀缺心理:Scarcity (lack of resources) and being worried about scarcity may impair cognitionPoor cognition in turn can lead to further financial difficulties and stress (feedback)Many other studies show correlations between environments on IQ (fostering vs. institutional care)Other environmental factors:In certain areas, pollution might contribute to the disparity in IQ scores

Major issue in certain places (e.g. Flint and New Orleans)Concerns have also been raised about the effects of social isolation and remote/digital education in children (e.g. during COVID-19)-On the Power of Mindset:Some believe intelligence is an innate, fixed property (i.e. it cannot be changed) whereas others believe intelligence is malleableThose who believe intelligence can be changed may exert more effort, may take on new challenges and may respond better to mistakes (growth mindset)-Evaluating ourselvesSome have proposed that intelligence is related to the ability to estimate intelligenceIf your cognitive ability is poor, you may be unable to realize it is poor (Dunning-Kruger effect); criticized recentlyLanguage:-Language is an arbitrary system of communication that combines symbols, such as words or gestural signs, in rule-based ways to create meaning-Acquired through observational learning, experimentation, reinforcement and shaping-In a sense, humans may be ‘programmed’ to learn and use language-Even when a language is absent in a population, that population may go on to develop oneE.g., Nicaraguan sign language in 1970s-Aspects of Language:Phonemes音素 are elementary sounds in a languageMorphemes语素are the smallest units of meaningSyntax句法 is the set of grammatical rules that control how words are put togetherThe set of rules by which we construct sentencesCorrect syntax does not always result in comprehensible languageContextual informationis important to understanding language-Emotion in Language:Phonemes may have an inherent emotional meaning

The phoneme /l/ (appearing twice in lullaby) tends to occur in pleasant, soft, tender scripts as well as in passive wordsThe phoneme /r/ (appearing twice in roar) tends to occur in unpleasant and active wordsThere have been attempts to use the affective qualities of words to produce a ‘dictionary of affect'Two dimensions contribute to affect: valence(x axis; negative to positive) and activation(y axis; high to low)-Sound Symbolism:Many people associate sounds with shapesThis suggests that sounds may also have an inherent symbolic meaning-Language difficulties:Language involves many brain areas; damage to any of these areas might cause deficitsBroca’s aphasia布罗卡失语症involves a difficulty in speech production, but comprehension can be intactWernicke’s aphasia韦尼克失语症involves a difficulty in both comprehension + speech productionAlexia/Dyslexia阅读困难involves difficulty in readingComprehension + speech production may be preserved-Language and the Brain:

-Language Development in Children:~7 months; babblingthat lacks meaning~10 – 12 months, common wordsemerge Spoken words may be altered/simplified Abnormal in autism spectrum disorders (ASD)-Sensitive periods for language:Acquisition easiest at 3 – 7 years of age, challenging after ~18 yearsIdea that language acquisition becomes much more difficult with age is generally believed, but is quite difficult to testMotivation for second language learning is differentContext in which second language is learned varies-Bilingualism双语:~50% of the world is bilingualIn North America, rates are lower (~20%)Early research showed that bilingual children processed language more slowly and had lower verbal scores. However, this research was problematic as:Studies were done primarily in children of low SES (socioeconomicsituation)Tests were done in English even for ESL (English as second language) studentsCurrent research suggests a different viewIn some studies, bilinguals have better cognitive abilities-Can Language Affect How We Think?Generally, we think of language as an expression of our thoughts. However, we may want to consider the possibility that language itself can change our thoughtsThe Saphir-Whorf hypothesispostulates that the structure of a language determines a native speaker's perception and categorization of experienceMixed support for the theory (e.g. Dani culture in New Guinea, Boroditsky’s research)Part of the reason why the SW hypothesis has not received strong support is that it is very difficult to testLanguage is also often contaminated by cultureIt is clear, however, that our learned social attitudes influence our thoughts (i.e. social psychology)