I used to have a pretty sharp mind, particularly when it came to simple arithmetic. I think age has begun to dull it. Case in point: recently I had to check a friend’s pulse rate. So I felt his pulse for 15 seconds and got 17 beats. 在这一点上, I wanted to call out the heart beats per minute. And at that point, my mind suddenly went blank. It started going through this chain, “行, I got 17 为 15 seconds. So what is it for a minute? It should be, what, 60 seconds over 15 时 17. Hold it, where is my iPhone? I need a calculator. No wait, 这是 17 for a quarter of a minute. 所以 17 时 4. Where is my calculator, dammit?!” Granted, it was a slightly stressful situation. But this is not at all the way my mind used to work.