The mere ownership effect is when you like something more just because you own it. Let's say you have a toy that you really like playing with. You like it even more because you have it and it belongs to you. This is the mere ownership effect at work.
It's like when you go to the store and you see a toy that you really want. You may spend a lot of time thinking about it and imagining how much fun you'd have with it. But if you never end up buying the toy, you might not think about it as much anymore because you don't own it. But if you do buy the toy, you'll likely enjoy playing with it even more because you own it.
This effect happens with all sorts of things, not just toys. It can happen with clothes, books, and even pets. When you own something, you feel like it's yours and that makes you happy. It's a special feeling that can't be replaced by anything else.
So remember, when you own something, you tend to like it more. It's the mere ownership effect!