The topic discussed in chapter nine of the book is "Intelligence and IQ testing." As you can assume this chapter talks about what intelligence is defined as, the different types of intelligence and the history of IQ testing.
The different intelligence types and history of IQ testing explains that even though we have come a long way in this field of study, there is still a lot that is theory or unknown. It is important to study this field so we can know exactly what intelligence is and how we can accurately determine what type of intelligence each person possesses and why. If we could determine what percentage of logic each person had between analytical, practical or creative, that would be very helpful so students know how they should study to best understand the material. Analytical is reasoning logic, practical is used to solve real world problems and creative is used to come up with answers to questions.