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. At that point, 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, “Ok, I got 17 for 15 seconds. So what is it for a minute? It should be, what, 60 seconds over 15 times 17. Hold it, where is my iPhone? I need a calculator. No wait, it is 17 for a quarter of a minute. So 17 times 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.