1.6 Why are certain repetitive activities more pleasurable than others? 15
1.6 Why are certain repetitive activities more
pleasurable than others?
Ivan crossed it all out and decided
to begin right off with something very strong,
in order to attract the reader’s attention at once,
so he wrote that a cat had got on a tram-car, and
then went back to the episode with the severed head.
Michael Bulgakov, The Master and Margarita
Let us turn our attention to the emotional side of mathematics,
more specifically, to the personal psychological experience of people
working with mathematical algorithms and routines.
I wish to formulate here some of my observations and conjec-
tures which may appear to be bizarre and out of tune from the
usual discourse on mathematics. However, I tested some of them in
a warm-up talk that I gave at the forum discussion Where do math-
ematicians come from? , part of a very peculiar conference,
that of the World Federation of National Mathematics Competi-
tions (WFNCM). It was held in July 2006 in Cambridge, England.
On my way from Manchester to Cambridge, four hours by train, I
had seen three people solving Sudoku puzzles. In one case, a lady
of middle age shared a table with me and I had a chance to watch,
in all detail and with a growing fascination, how she was solving
an elementary level Sudoku puzzle. Her actions followed a certain
rhythm: first she inspected the puzzle row by row and column by
column until she located a critical cell (whose value had been al-
ready uniquely determined by the already known values in other
cells) and then, with obvious agitation, checked that was indeed
the case, happily wrote the digit in, smiled with a childish satisfac-
tion, relaxed for a few seconds, and, after a short pause, started the
The next day, in my talk at the conference, I pointed out that,
from a mathematical point of view, solving an elementary level Su-
doku puzzle is nothing more than solving a triangular system of
Boolean equations by back substitution, something very similar to
what we do after a Gauss–Jordan elimination in a system of si-
multaneous linear equations. But has anyone ever seen people on
a train solving systems of linear equations from a
Why is Sudoku popular, when systems of linear equations are
not? (Actually, I was slightly wrong: at the time of my talk, I was
unaware of Kakuro, which combines linear and Boolean equations.
But one still has to see whether Kakuro beats Sudoku in popular-