“Just about everything we choose to do can direct our cognition up or down. The effect may be negligible or significant, but it all adds up. The more challenging choices we make, and the longer we do them, the greater the benefit—usually by a considerable amount. It does not really matter whether we work primarily with people, things, or data. What matters is whether the work is challenging or routine. Schaie shows that we need to remain engaged. As is implied in his studies and demonstrated in others, a variety of stimulation matters a great deal to our brainpower.”