* A computer or phone with more RAM can run faster because it can hold more in memory. Higher RAM invariably compromises your battery life, though—especially on a phone. Apple recently resisted adding more RAM to its iPhone for this reason. Since the RAM on a computer is always active, and information is constantly moving through it, that activity sucks up a lot of power. Our attentional space may be limited for a similar reason. Some scientists argue that it might have been “biologically expensive” for us to have evolved to have a larger attentional space, because of how activated our brain would need to be—and how much energy it would need to consume—to keep that information simultaneously activated. In addition, over the last 2.5 million years, our daily tasks weren’t nearly as complex as the knowledge work we do today. Our brain consumes enough energy as it is. While it makes up just 2–3 percent of our body mass, it burns 20 percent of the calories we take in. The fact that our brain’s capacity is limited in this way allows us to conserve energy, which may have aided our chances at survival.