Perspectives on Individual Differences in Intelligence
-Hereditarian
-Unitary Models
-Multifaceted Models
-Domain-Specific Models
Hereditarian Theory of Intelligence -2 claims:
1) intelligence is unitary Pa reflection of an all-purpose system of process that permeates all intellectual activity) and generic Pintelligence is measurable using tests that are meaningfully converted into numbers that reflect the amount of intelligence a person possesses) 2) intelligence is genetically determined Pintelligence is found in the genes people inherit)
Multifaceted View
-claims that people may display superior talent or skill in one intellectual domain without necessarily being superior in other domains
-there are many different and relatively autonomous domains of intelligence
Four Developments of the Hereditarian Theory of Intelligence
- Theory of Evolution: focuses on individual differences and natural selection
- Rise of Materialism: the view that we label mental activity reflects only brain processes 3) Rise in Psychological Experimentation and Measurements: sophisticated techniques for investigating and quantifying human behavior 4) Universal Education
Francis Galton
-Darwin’s cousin and a founder of the intelligence testing movement
-The first to suggest that fingerprints be used for personal identification
-With Pearson, they developed the formula for correlation
Correlation
-a measure of the degree to which two measurements are linearly related
-correlations range between +1 and -1
-just because two measures are correlated does NOT mean they have a causal relationship Pbut when there is a causal relationship, they absolutely have a correlational relationship)
Positive Correlation
-indicates that when scores increase, scores on the other measure tend to increase as well -ex: height and weight are positively correlated
Negative Correlation
-indicates that when scores on one measure increase, scores on the other measure tend to decrease
-ex: smoking and longevity are negatively correlated
Lack of Correlation
-when scores on one end increase, scores on the other measure neither increase nor decrease
-ex: the last digit of a social security number and one’s annual income are not correlated
Galton’s Findings on Correlation
-proposed that intelligence is primarily a reflection of energy and the perceptual acuteness of the senses
-in his study, he showed that mentally retarded people did not discriminate heat, cold and pain as well as “normal” people
-Galton’s findings were taken up by James Cattell who started to use them on college students
Alfred Binet
-one of the founders of experimental psychology
-conducted research on hypnotism, cognitive development, memory and creativity
-proposed that for children with disabilities, more complex tests should be given
-to determine intelligence, the age associated with the most difficult tasks that the child could perform was his mental age, which was then compared with the child’s chronological age -Binet did not believe that IQ score was a measure of intelligence Pintelligence is too complex to render it with a simple number)
William Stern
-Proposed that mental age should be divided by chronological age and then multiplied by 100 to produce the familiar IQ score
IQ Tests Since the 1900s:
-Stanford-Binet Pmodification of Binet’s original test)
-Wechsler Scales for Children PWISC – verbal and performance IQ)
-Wechsler Scales for Adults PWAIS – verbal and performance IQ)
-The Raven’s Matrices Pnon-verbal test) –SAT Pcollege entrance IQ tests)
Charles Spearman:
-People who do well on any subtest of the IQ test tend to do well on any other subtest.
-The various subtests are positive correlated.
-He labeled this idea “g” to stand for the general factor that underlies all intellectual activity
Fluid Intelligence
-general component that reflects some genetically determined biological aspect -i.e. problem solving strategies
Crystalized Intelligence
-specialized components that reflect various learned skills
-i.e. knowledge from prior experience
Information Processing
-measuring the speed and efficiency with which people can carry out any component of cognitive processing
Inspection Time Task
-Subjects are given two parallel vertical lines joined at the top by a horizontal line
-One vertical line is longer than the other
-Over time, the image is shifted from left to right and the subjects have to guess which line is longer.
-Inspection time refers to how long the stimulus is exposed to the subject
-People whose inspection times are short tend to score higher on IQ tests
Problems with the Information Processing Perspective on Intellectual Differences
-not every researcher finds a correlation between speed and IQ performance
-relies too much on establishing correlations between measures of information processing and IQ scores
**what is lacking are demonstrations that measures of information can predict performance on real life tasks better than conventional tasks
Physiological Basis of Intelligence
-researchers speculate that more intelligent people have more synapses among neurons, easily reconfigure connections among neurons, and more efficiently metabolize energy
Are Smart Brains Metabolically Efficient?
-Using PET scans, studies have shown that those who score high on IQ tests or are familiar with specific games, tend to use less cortical metabolic rates and use less energy
Neural Conduction Rate and Smart Brains
-People who score higher on IQ tests may have a higher rate of neural conduction -Shorter latencies imply faster neural conduction
Creativity, Social Skill and Practical Intelligence
-the main point is that if we expand our sense of intellect, we will find that people are not equally skilled in all areas
-these skills are not normally emphasized in school
Creativity
-most IQ tests have no measure of creativity
-hard to measure objectively
-creativity bears little relationship to scores on IQ tests
-it is a different kind of intelligence
Social Skill
-hard to measure objectively
-weakly related to IQ tests
Practical Intelligence
-has to do with the actual attainment of goals that are valued
-known as tacit knowledge and “street smarts” -essentially unrelated to standard IQ tests
Gardner’s Six Distinct Categories of Intelligence
-verbal
-logical
-musical
-spatial
-bodily-kinesthetic
-social-emotional
**intellectual skill in one category is unrelated to intellectual skill in any other category
Evidence for Gardner’s Frames of Intelligence
-He uses brain damage, isolated talents, anthropological evidence and the nature of mental operations to support his theory
-Brain damage: damage can interfere with one intellectual competency but leave others intact -Isolated talents: people who are unusually talented in one realm, like music or art, but are unremarkable in other areas
-Because all of these intelligences are different, it suggests qualitative differences among categories of intellectual skill
IQ Industry and Academia Claim:
-reasoning and language skills are of the utmost importance
Criticisms of Gardner’s Frames
-Gardner’s theory fails to explain the positive correlations among subtests of IQ tests
-It seems to divide human intellect into categories in an arbitrary way
-Gardner leaves out other categories that might be considered types of intelligence
Guenther’s View of Intelligence
-it is multifaceted
Evidence for a Genetic Basis for Intelligence
-Familial IQ Correlations: as seen by measuring identical twins reared apart, genes are a primary determinant of intelligence, at least measured by IQ tests.
-Identical twins reared apart are almost as correlated as identical twins reared together.
Problems with the Evidence Supporting a Genetic Basis for Intelligence
-the environment can cause a huge difference in IQ and intelligence
-some infants placed in different environments may have had prenatal problems and this might be the reason for their low IQ scores
-similar people living together tend to have correlated IQ scores
-when looking at twins reared apart, it does not identify which genes produce the high correlations
The Role of Environmental Factors in Intellectual Differences:
-Garber’s Study: he placed a group of mentally retarded children in an extensive home enrichment program and by age 6, the children scored 30 points higher than did a control group -Carolina Abecedarian Project: placed low-income children in enriched environments and they scored higher on tests of intelligence even 7 years later
Parents who Reared Intellectually Competent Children Do 3 Things:
- provide a structured, safe and interesting physical environment for their children
- spend a lot of time helping their children solve problems
- establish and enforce clear-cut rules, but in a loving and respectful manner
Generational Environmental Changes: IQ Scores Are Rising:
-The average gain is 3 IQ points per decade
-Most IQ tests have to be restandardized in order to keep the mean equal to 100.
-People who score 100 on an IQ test today would have scored 115 in the year 1947.
-Possibilities why IQ scores are rising: television, urbanization, prolonged schooling, nutritional improvements, increases in height, etc.
-Hence, it must be something in the environment that is changing the IQ scores over decades.
Ethnic Differences in IQ Performance
-Primarily due to environmental and cultural factors
-Most stereotyped things: Asians are super smart, minorities aren’t as smart, Europeans have more intellect, etc.
Evidence Against a Genetic Basis for Ethnic IQ Differences -Environment can drastically affect group differences
Heath’s Cultural Differences Study:
-African-American children from low-income families: skilled at responding to novel situations, defending themselves against a verbal insult and telling creative stories
-European-American children from middle-income families: good at responding to requests, responding quickly when timed and answering “why” questions
***poverty or a lack of formal education does not necessarily depress intellectual development Cole, Gay, Glick and Sharp’s Study on Kpelle Tribespeople:
-The Kpelle sorted objects into functional groups, i.e. knife with orange
-Westerners sorted objects into taxonomic groups, i.e. knife with fork
***The Kpelle valued functional things more than the typical taxonomic grouping.
Sex Differences in Intellectual Competencies
Males: tend to do better in mathematical-spatial abilities
Females: tend to do better in tests of verbal and perceptual abilities
*men and women do not differ in IQ scores, vocabulary tests or reasoning tasks
Genetic Basis of Sex Differences in Cognition
-Boys are more likely to be encouraged to pursue careers in science, engineering, mechanics Pwhere math and spatial skills are required)
-Girls are more likely to be encouraged to pursue careers in teaching and in child rearing Pwhere communication skills are important)
-Sex hormones such as testosterone are known to influence the organization of the mammalian brain during critical periods in prenatal development
-Women exposed to prenatal androgens in utero better at spatial tasks
-Levels of progesterone and estrogen are higher during the midluteal, late menstrual phase, and this is when women do worse on cognitive tasks that favor men Plike spatial rotation) -Men do better at tasks that favor women during the spring when their testosterone levels are relatively low
How do hormones affect our cognitive functioning?
-May affect how the cerebral hemispheres distribute their function Pi.e. left hemisphere = language, right hemisphere = spatial processing)
Kimura’s Suggestion
-The organization of functions within the left hemisphere differs between the sexes
-Women make use of language in the anterior left region whereas men use the posterior left hemisphere
-Aphasia occurs more in women when the damage is near the front of the left hemisphere, but more often in men when the damage is in the posterior area of the left hemisphere
Environmental Explanations of Sex Differences in Cognition
-There is a possibility that sex differences in cognition are due mostly to environmental factors
-In many studies, males and females performed on average about the same
Carol Tavris’ Opinion
-Male and female brains learn, reason and process information similarly
-There is a bias today of excluding women from the sciences even though they may have the same amount of intelligence in that field as men
Summary and Conclusions
-Not genetics or environment alone, but together Pnature + nurture)
-IQ tests are known to be moderately correlated with grades in school, occupational status, and success in an occupation
-Given that controlled experiments are ethically and biologically impossible, we may never completely understand the precise contributions that genes and environmental factors make to individual intellectual differences