1. Varieties of Intelligence

• The basic message of this book is that one’s environment has great power to influence intelligence. Specifically, it’s about the roles that schools and cultures play. Differences in IQ between ethic groups can be traced to historical disadvantages as well as social practices that can be changed. Intelligence is a general mental capability that involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. While there are other definitions that embrace things like memory and mental speed, this definition works for this book. Authors such as Howard Gardner also break intelligence into up to eight components. Emotional intelligence is also supported by some authors.
• There are two components of intelligence. Your general intelligence deals with what you know and what you know how to do. Fluid intelligence deals with your ability to solve novel and abstract problems. This type of intelligence tends to decline with age while your general intelligence gradually increases. For the purpose of this book, IQ scores combine the two types.

2. Heritability and Mutability

• There are two schools when it comes to the sources of intelligence. The hereditary school believes that 75% to 85% is inherited. In other words, it’s in your genes that get together at the moment of conception. The environmentalist school, which Richard sides with, sees intelligence as 50% or less inherited. In this most technical chapter Richard makes a convincing case for the environmentalist school. Key data comes from adoptions, as adopted children have IQs similar to their adopted parents. The details of studies of adoptees and twins is fascinating, and Richard does an excellent job of explaining how biases influence what he sees as the misguided conclusions of the hereditary school. While children born to poor families generally have lower IQs, there is no reason why poor kids can’t have higher IQs if their parents provide an environment more like what is usually found in wealthier homes. The bottom line here is that IQ can be modified by changing the environment.

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