These brain-training exercises are formatted as stimulating puzzles. They are designed to help develop mental skills in two ways:

• First, they will help you to build mental stamina for sustained concentration, much as aerobics builds physical stamina for sustained exertion. The ability to focus attention is an essential first step for conscious memory.
• Second, the exercises introduce, in an entertaining format, so many different kinds of data — math, verbal, spatial, logic, etc. — that some of it is bound to be new to you. That new data — and more important, the experience you gain in how to organize data so you can locate a solution — will build links among your brain cells that, later, can help you learn new data and spot the most effective pattern to cope with it.
  

Use the Hints when you need a boost to get started solving the task. These exercises are there to stimulate neural activity, not to frustrate it.