Intelligence & IQ Testing

Genetic influence on IQ can be studied through three main methods:
- Family studies
- Twin studies
- Adoption studies

Family studies provide evidence that IQ runs in families.
Findings include:
- Individuals with higher intellectual achievement often have biological relatives who also exhibit high intellectual achievement.
- Highly intellectual individuals tend to have many highly intellectual first-degree relatives (e.g., parents, siblings).
- The number of second-degree relatives (e.g., first cousins) who share similar levels of intellectual achievement is significantly lower due to increased biological distance.
Limitation: It is difficult to determine whether the observed correlation in IQ among relatives arises from genetic factors, environmental factors, or a combination of both.

Twin studies demonstrate that the correlation of IQ scores among identical twins is higher than that among fraternal twins, suggesting a strong genetic influence.
Key findings include:
- Identical twins raised apart exhibit similar IQ levels to those raised together.
- If genetics were the sole influence, then the IQ correlation for identical twins should approach 1.0 (perfect correlation).

Adoption studies help distinguish between genetic and environmental influences on IQ.
Findings include:
- Adopted children who come from extremely deprived environments show an increase in IQ when placed in an enriched environment.
- Adoptive children's IQs tend to resemble those of their adoptive parents when they are younger, although this resemblance begins to decrease as they get older.

The perception of IQ can influence academic behavior:
- Individuals who view their IQ as fixed are less likely to take academic risks (e.g., enrolling in advanced courses).
- Conversely, those who perceive IQ as flexible tend to embrace more academic challenges.
Family size can influence IQ:
- Children from larger families tend to exhibit slightly lower IQ scores than children from smaller families.
- Within families, the relationship between birth order and IQ is weak.
Educational exposure correlates with IQ:
- The number of years of schooling correlates positively with IQ, and vice versa.
Early intervention programs can lead to short-term IQ increases, which are associated with lower high school dropout rates, but these increases are often not enduring.
Teacher expectations can have a small influence on students' IQ scores.

Poverty can negatively affect IQ:
- Individuals living in poor environments may experience a decline in IQ scores over time.
- Factors such as prolonged malnutrition and exposure to lead are more common in impoverished situations and can lower IQ.
Flynn Effect:
- Average IQ of the population has been rising approximately 3 points every 10 years.
- Possible explanations include:
- Improved experiences in taking IQ tests.
- Contemporary generations are more skilled in processing larger amounts of information quickly.
- Generally better nutrition among the population.
- Parents are more focused on fewer children and have better access to intellectual resources.
- Today's children and adolescents spend more years in school than previous generations.

Most research indicates few or no significant average differences in IQ between males and females.
Findings suggest:
- Males tend to show greater variability in their IQ scores compared to females.
- Females often excel in verbal tasks and recognizing emotions, whereas males tend to perform better in spatial abilities and complex mathematical reasoning.

Some observed differences in verbal and spatial abilities may have biological origins (e.g., genetic factors).
Most differences appear to stem from environmental influences:
- Infants of both sexes show little to no difference in spatial or counting abilities.
- Sex differences in these areas typically emerge later in life, likely influenced by differing problem-solving strategies.

Research identifies small IQ differences between ethnic groups.
Explanations for these differences include:
- They largely stem from environmental factors, as improvements in environmental conditions lead to diminished differences, supported by adoption studies.
- Test bias could play a role in outcomes, where intelligence tests may favor certain groups over others.
- Stereotype threat—the fear of confirming a negative stereotype about one’s group—can adversely affect test performance.

Creativity is often assessed through divergent thinking tests, which measure the ability to generate various solutions for a single problem, such as the “Uses of an Object” test.
Additionally, convergent thinking, which is the capacity to identify the single best answer to a problem, is also important.
Creativity exhibits a weak correlation with IQ.

Emotional intelligence is the ability to comprehend and respond to one’s own and others’ emotions, applying that understanding in everyday situations.
Key components of emotional intelligence include:
- Recognizing emotions
- Appreciating emotions
- Controlling emotions
- Adapting emotions to different contexts
Emotional quotient (EQ) is proposed to be as significant as IQ for effective functioning in personal and professional environments.
Emotional intelligence may enhance job performance but does not clearly differ from personality traits.