When a wiggly little bead of light catches a dog's eye, nothing in the world matters more than capturing it. Unfortunately, "it" is just an ungraspable bundle of massless photons. The lack of closure in laser-beam chasing could be messing with your dog's head.
Dogs (and some cats) instinctively chase these bright-red dots simply
because the dots move, said Nicholas Dodman, a professor of animal
behavior at Tufts University's Cummings School of Veterinary Medicine.
Movement automatically stimulates their innate prey drive,
which explains why lower-on-the-food-chain animals such as rodents and
rabbits often freeze in place as a survival strategy. Although dogs aren't so discerning when it comes to color, their eyes contain a high preponderance of light-sensitive cells called rods for top-notch motion detection.