Ants with little cookie bits can walk forward as per usual, so they navigated the 90-degree turn just fine. But when they had to walk backwards to drag bigger cookies, they missed their turns, going on and on in the same direction they headed out in. Backwards ants aren’t able to recognize their surroundings in reverse, so they don’t realize that they have to turn to get home. And it’s the same deal if you drop the ants in a new location. Forward-moving ants can use visual cues to get back to the nest, but backward-moving ants head off in the wrong direction.