But how do you figure out how much information an animal can see in one second? (Hint: you can't just calmly ask a ground squirrel about its personal life. I've tried.) The team examined a trait called critical flicker fusion frequency, which measures how fast the eye can process a blink of light. The test flashes a light, say, four times a second, and checks to see if the eye contracts upon each flash. If the animal's flicker fusion frequency is lower than four flickers per second (4 hertz), those flashes won't look like flashes at all; it'll seem like a steady light. Imagine watching a strobe light but making it go faster and faster and faster until it's not strobing anymore--it's just a light. That moment where it becomes a steady light is what the researchers are looking for.