reminds me of a very interesting demonstration from martin gardner. draw a 6x6 grid, and write a random digit in each cell, proceeding row by row. now count the

reminds me of a very interesting demonstration from martin gardner. draw a 6x6 grid, and write a random digit in each cell, proceeding row by row. now count the number of pairs of consecutive (x, x) going horizontally versus vertically; you will almost always get doubled numbers in the columns because that's how random numbers work, but almost never in the rows, because when people are trying to generate "random" numbers by hand they avoid runs or other patterns.