I was reading some PowerPoint slides by a CalTech professor Mark Changizi, when I came across an interesting word: subitize 'to judge the number (of objects in a group) rapidly, accurately, and confidently without counting them'. It's from the Latin word subitus 'sudden', ppl of subeo 'to come / go under, succeed'. It was coined in 1949 in the field of psychology. Changizi has recently co-authored a paper on letter shapes that was mentioned in this article in the Daily Telegraph.

Interesting word, Zmj. It made me wonder about exceptional talents that autistic people sometimes have in being able to accurately know the number of objects present, when they are in a large group (remember the "Rain Man" movie?). Would that be subitizing?

I think it's more in the real of being able to see three or four objects without counting them. The knowing how much change somebody dropped or the number of matches is a little out of the ordinary.