Reliability of IQ Scores

Test-Retest Reliability: Consistent IQ score across measures

  • Reliability of IQ scores depend on age. Adults IQ scores remain stable over time

    E.g. Deary et al, 2000

    Looked at childhood IQ score and later when they were elderly, IQ scores correlated about 0.73

Infancy and childhood IQ: These IQ scores will not predict adult IQ scores

  • When we test infants, we cannot ask advanced questions

  • The tests are measuring different things (Adult vs Child IQ tests)

Visual Habituation

We can test an infant by using an object/stimulus to see how long they will look at it or how long till they get bored.

E.g. When a baby become bored of a toy, they become habituated

Why?

  • This shows that infants who habituate faster have higher IQ scores

  • More intelligent babies take in more info from novel stimuli more quickly

  • Infants who are interested in new things habituate faster and learn more things

Validity of IQ

Predictive Validity: Does the measure predict what is to happen

IQ tests can also be used for occupations like lawyers, doctors, etc

  • Job interview performance and occupational performance has a weaker correlation (0.5 r)

IQ predicts criminal behaviour

  • IQ is lower in young offenders

IQ predicts health outcomes

  • The lower your IQ, the more you tend to experience illness

  • Health Literacy: How well people understand health-related information to make health decisions

Social Class and IQ Scores

  • When we control for poverty, we still see a correlation between poverty and IQ

Genetic and Environmental Influences on IQ

Heritability: How much of IQ is genetically determined through studies like family studies

Family Studies: The more genetically related we are to someone, the higher the correlation with IQ is. However, critics say that there may be influence on IQ if family are in the same or different environment

Twin Studies: Comparing IQ between two sets of twins

  • Found that identical twins correlates of 0.7 to 0.8 and fraternal is 0.3-0.4

  • Twins who are apart still have similar IQ scores but environmental influences still affect IQ

Adoption studies: Comparisson of adopted children to their adoptive parents and biological parents

  • Found that adopted children have similar IQ as biological parents

Significance of studies: When we are talking about IQ and psychology, it is important to consider environmental influences and not just biological factors

Nature and Nurture: We are born on a genetic influence on Iq but our environmental influences how the IQ develops depending on the typ of environment we live in

Amount of Schooling: People with more schooling have greater amounts of synapses which shows more neuro-communication

Poverty and IQ: IQ scores decrease over time if they are living in a poor environment

  • Lack of nutrition is linked to lower grades and exposure to lead

Flynn Effect: Average IQ of the population arise over time with around 3 points per decade

Why? Environmental influences!

  1. Better nutritions

  2. Increased test sophistication (more experience with IQ tests

  3. Incresed complexity of modern world (processing a lot of information on smartphone everyday)

  4. Changes in home, school, and culture

    The Reverse Flynn Effect: Average IQ of the population may be decreasing

    • Verbal reasoning, matrix reasoning, and letter/number series have been decreasing

Group Differences in IQ

Often seen as a controversial topic because of research on gender differences and ethinic groups

Sex Differences in IQ: Differences between IQ of men and women are more likely due to environmental factors then biological

Specific Mental Abilities of Females

  • Females tend to score higher on verbal tasks

  • In childhood, women tend to be better at artihemetic calculation and emotional intelligence

Specific Mental abilities of Males:

  • Higher spacial ability

  • Higher mathematical reasoning skills

Potential Causes of Sex Differences:

  1. Verbal and spacial ability influenced by hormones

  2. Environmental influences

    1. Sex differences in problem-solving strategies

    2. Experience/training

Differences between Ethnic Groups

  1. Asian Americans tends to score higher than White Americans

  2. African and Hispanic Americans tend to score lower than White Americans

Why

  1. Environmental factors

    • Poverty, health, prejudice, discrimination, and schooling

  2. Within-Group Heritability: How much is IQ inheritable within a group which is likely due to genetics

    Between-Group Heritability: The extent to how IQ is inheritable between groups likely due to environmental influences

  3. Stereotype Threat: The fear we may conform to a negative stereotypes