Seeing Numbers

At a quick glance, could people tell the difference between a group of 20 dots and a group of 30? What about 20 and 21? It seems like there must be a point at which they would simply be guessing, but recent research suggests otherwise. Given enough opportunities, people consistently perform better than chance on this kind of task even when the numerical difference is extremely small, according to a study published in the Journal of Numerical Cognition. The researchers tested two mathematical frameworks for thinking about this situation: one with a hard limit on the fine numerical differences people can perceive and one without. They found their data fit better with the limitless model, suggesting that even with numbers as high as 100 versus 101, the task would become harder but not impossible.