Media Object: TI Bird in a Cage Science Snackbook

When your eyes and your brain work together, they can do a lot of things—even make a bird appear in an empty cage. This Science Snack from Exploratorium Teacher Institute teacher Lori Lambertsen shows how you can take advantage of the cones in your eyes to form an after-image and see things that aren't really there. Like other Snacks, this activity is classroom-tested and can be done with inexpensive, easy-to-acquire materials.