Dogs struggle to pick out people on a small phone screen. This is because dogs have a higher flicker sensitivity than we do - to a dog, a video on a small phone screen consists of jerky shapes and lights. They are great at detecting motion, doing so at least 25% faster than us, but will have difficulty picking out images on a screen. Conversely, your dog might be able to recognize you on a large, high-definition television, where the images are bigger and much less compressed.