This experiment changed our understanding of parasite resistance

It's common scientific wisdom that parasite resistance comes from repeated exposure to a parasite. But a new study has turned this idea on its head. Guppies who were removed from rivers swarming with parasites actually evolved an improved parasite tolerance in just a few generations. Here's how it happened. » 11/06/13 1:00pm 11/06/13 1:00pm

Answer quickly: are there more fish on the left or right side of this image?

You'll notice right away that choosing the correct side without counting the fish individually is pretty tough. This difficulty stems from the fact that humans can only assess relative quantities by snap judgment under certain conditions. Take away six fish from the right-hand side, for example, and this task becomes… » 2/16/12 8:35am 2/16/12 8:35am