My 2 year old play with the following toy at our home. https://www.amazon.com/Melissa-Doug...oys-and-games&ie=UTF8&qid=1321656652&sr=1-107 It is basically, when you put the correct animal block in the correct place, it makes the sound of that animal. I can see some sensor in the wood piece and in the board; it can be easily explained how the toy works. What is puzzling me is, whenever I turn off the bedroom light at night before going to bed, this toy makes a cat sound. Each and every night, for years. In my puzzle board, the cat piece is missing, so the sensor in the cat block is always open. Can someone explain exactly what causes the cat sound, when I turn off the light?