History of Intelligence Testing (Intro Psych Tutorial #117)

Summary

In this video, Michael Corayer reviews the history of intelligence testing, starting with Sir Francis Galton, the founder of psychometrics. Galton's work on measuring intelligence and its heritability led to the development of the Binet-Simon test by Alfred Binet and Theodore Simon. This test introduced the concept of 'mental age' and was later adapted by William Stern into the Intelligence Quotient (IQ). The video discusses the evolution from ratio IQ to deviation IQ and highlights significant contributions by Lewis Terman and David Wechsler in standardizing intelligence tests. It emphasizes that IQ tests measure potential ability rather than direct performance and concludes with Terman's longitudinal study linking early IQ to future success.

Takeaways

• 😀 Sir Francis Galton is considered the founder of psychometrics due to his interest in measuring people and inventing statistical techniques for calculating correlation.
• 🧠 Galton's work 'Hereditary Genius' aimed to find a link between intelligence and inheritance, influenced by his half-cousin Charles Darwin's ideas on survival advantage.
• 📏 Galton attempted to correlate various physical measurements with intelligence but found no strong connections.
• 🏫 The French education system's reforms in the late 1800s led to the creation of the Binet-Simon test by Alfred Binet and Theodore Simon to assess students for appropriate educational placement.
• 🌟 The concept of 'mental age' emerged from the Binet-Simon test, allowing students to be judged by their cognitive development relative to their peers.
• 🔄 William Stern adapted the concept of mental age to create the Intelligence Quotient (IQ), initially using a ratio IQ based on mental age and chronological age.
• 📉 The ratio IQ fell out of favor due to its limitations in adulthood, leading to the development of deviation IQ, which compares an individual's score to the average for their age group.
• 🎓 Lewis Terman adapted the Binet-Simon test to create the Stanford-Binet Intelligence Scale, which is still in use today with deviation IQ scoring.
• 📚 Terman's longitudinal study showed a correlation between early childhood IQ and future success in education, job status, and income.
• 🧑‍🔬 David Wechsler developed the Wechsler Adult Intelligence Scale and other versions for different age groups, focusing on verbal responses and various cognitive abilities.

Q & A

Who is considered the founder of the field of psychometrics?

Sir Francis Galton is considered the founder of the field of psychometrics.

What was Galton's belief about the inheritance of intelligence?

Galton believed that intelligence was inherited, as he explored the association between intelligence and inheritance in his book 'Hereditary Genius'.

How did Galton attempt to connect physical measurements to intelligence?

Galton measured various physical features such as reaction time, sensory acuity, muscular power, body proportions, and head size to find correlations with intelligence, but he didn't find strong correlations.

What was the purpose of the Binet-Simon test created by Alfred Binet and Theodore Simon?

The Binet-Simon test was created to help sort students appropriately into classes where they would benefit the most, given the diverse educational backgrounds of children in the French education system.

What is meant by 'mental age' as introduced by the Binet-Simon test?

Mental age refers to the average performance level of students of a particular age on the Binet-Simon test, allowing for a comparison of a student's performance to the average for their age group.

How did William Stern contribute to the concept of intelligence quotient (IQ)?

William Stern adopted the concept of mental age to create the intelligence quotient (IQ), which is a comparison between mental age and chronological age, resulting in a ratio IQ score.

What is the difference between ratio IQ and deviation IQ?

Ratio IQ compares mental age to chronological age to get an IQ score, while deviation IQ compares an individual's score to the average score for their age range and then multiplies that by 100 to get the IQ score.

Why did the concept of ratio IQ become less useful with age?

The concept of ratio IQ becomes less useful with age because mental age doesn't increase significantly beyond a certain point, making it difficult to compare individuals across different age ranges.

What was the significance of Lewis Terman's longitudinal study on intelligence?

Lewis Terman's longitudinal study showed that early childhood IQ could predict future performance in life, such as higher levels of education, income, and job status, debunking myths about high IQ individuals.

What is the current status of the Stanford-Binet Intelligence Scale developed by Lewis Terman?

The Stanford-Binet Intelligence Scale is still in use today, but it has evolved to its fifth edition and now uses deviation IQ scoring instead of the original ratio IQ.

How does the Wechsler Adult Intelligence Scale differ from the original intelligence tests in terms of administration and content?

The Wechsler Adult Intelligence Scale, unlike the original tests, is administered in person by a trained psychometrician and involves multiple parts that assess various cognitive abilities, with most responses being verbal rather than written.