In an interview, David Foster Wallace told Larry McCaffery this --
“For most of my college career I was a hard-core syntax wienie, a philosophy major with a specialization in math and logic. I was, to put it modestly, quite good at the stuff, mostly because I spent all my free time doing it. Wienieish or not, I was actually chasing a special sort of buzz, a special moment that comes sometimes. One teacher called these moments 'mathematical experiences.' What I didn’t know then was that a mathematical experience was aesthetic in nature, an epiphany in Joyce’s original sense. These moments appeared in proof-completions, or maybe algorithms. Or like a gorgeously simple solution to a problem you suddenly see after half a notebook with gnarly attempted solutions. It was really an experience of what I think Yeats called 'the click of a well-made box.' Something like that. The word I always think of it as is 'click...'”
“... It was real lucky that just when I stopped being able to get the click from math logic I started to be able to get it from fiction. The first fictional clicks I encountered were in Donald Barthelme’s 'The Balloon' and in parts of the first story I ever wrote, which has been in my trunk since I finished it. I don’t know whether I have that much natural talent going for me fiction wise, but I know I can hear the click, when there is a click. In Don DeLillo’s stuff, for example, almost line by line I can hear the click. It’s maybe the only way to describe writers I love. I hear the click in most Nabokov. In Donne, Hopkins, Larkin. In Puig and Cortázar. Puig clicks like a fucking Geiger counter. And none of these people write prose as pretty as Updike, and yet I don’t hear the click in Updike.”
I can't say I really grok what Wallace meant by a “click.” If only someone had hooked him up to an MRI or PET scanner while he was reading, and asked him to report the “clicks,” back when we had the chance...