Humans tend to absorb information in the brain, but make decisions with their gut. That’s why, in the face of simple instructions on how to be healthy, we still tend to overeat, get too little exercise, and die of completely unnecessary causes at too early an age. The empirical knowledge just doesn’t get translated into behavioral changes — we don’t “internalize” it, to use shrinkspeak.

There is no doubt that if we watched every clinically-obese person we know die before age 40, we would take some action. That there are so many unhealthy but living folks at advanced ages makes it easy to say to ourselves that we have plenty of time, or that it won’t matter.

That may well be the case with HIV. The infection rate in Western society is on the rise again, after a drop for some years. Notably, it is in less educated groups primarily, but an alarming number of well-educated folks who should certainly know better are practicing unsafely as well. Possibly it is because they lack the experience of having seen their friends wither and die in their prime. It may well be the the additional denial afforded by the presence of effective drugs that has caused it. But I also believe it is simply due to familiarity. Early on, it was a mysterious plague, then a death sentence, now it’s more on the order of an inconvenience, so far as our denial system is concerned.