What does estimation have to do with the perfect world of numbers?

Steve sent me an interesting story in Science News about new research done on the correlation between the ability to estimate quantity and skill in algebra. Knowing very little about the study design, it is hard to argue for (or against) such a correlation. It does, however, seem quite counter intuitive to me. Algebra is primarily about symbol manipulation. Those that have trouble in it, tend to have trouble manipulating symbols in the correct way. To me, the figures of music seem to have more in common with algebra than the ability to guess the number of jelly beans in a jar. Be that as it may, math does teach us that some of the best results are counter intuitive.