A childhood belief about speaking

When I was little, I didn't really understand echoes. My back yard faced a mountain, so I could shout and a second or two later, I would hear the echo. I used to believe that there was another little boy out there shouting back at me. I would get mad because I used to think he was repeating everything I said just to get on my nerves. I would spend several minutes marching back and forth across my back yard arguing with myself...