In this chapter you will learn
 

• What some problems are in defining and measuring intelligence
• Some of the neural characteristics that contribute to intelligence
• The role of heredity and environment in forming intelligence
• How aging, intellectual disability, autism, and attention-deficit/hyperactivity disorder affect intelligence

This chapter expands the understanding of cognitive processes begun in Chapter 12 by exploring the biological bases of intelligence. Intelligence is defined but, recognizing that the meaning of intelligence is controversial, the ensuing discussion focuses on problems of measurement (intelligence tests) and the structure of intelligence (unitary vs. general factor). Part two of the chapter is devoted to the biological origins of intelligence. A survey of brain structures and neural characteristics (e.g., nerve conduction velocity) yields evidence for both a general factor and specific abilities. The Application segment discusses animal tool users, and an updated Application reveals that drugs used to treat narcolepsy and attention disorders are being abused by others attempting to enhance memory and performance. Following a discussion of the influences of heredity and environment, the final section of the chapter takes up deficiencies and disorders of intelligence. The effects of aging on intelligence are first outlined, with the particular effect of nutrition being a factor. Intellectual disability is defined and examined, and Autism Spectrum Disorders are discussed in detail. Finally, Attention Deficit Hyperactivity Disorder is discussed, and the In The News segment discusses a new test for ADHD.