Joggers love their headphones. If you ask them why, they’ll tell you music keeps them motivated. The right song can transform what is by all rights an arduous half hour of ascetic masochism into an exhilarating whirlwind (or, in my case, into what feels like only 25 minutes of ascetic masochism). Music-driven joggers may be experiencing a pleasurable diversion, but to the other joggers and bikers in their vicinity, they’re Tasmanian Devils. In choosing to jog to the beat of someone else’s drum rather than their own, headphone-wearing joggers have “blinded” themselves to the sounds of the other movers around ...