Most of the time, this mental picture is only at the level of the subconscious mind. You may not be consciously aware of the picture. And yet, the image is still there, and it will still create a craving for food, and a to eat. This can also happen if you eat while working on the computer, or eat in bed, or eat while you drive, or eat while watching other people eat, and so on. Soon, just about everything can cause you to unconsciously see food, and then these unconscious images can make you "feel" cravings for food, and push you to eat.