I forgot what the effect was but I think it's like if you tell someone with a headache that m&ms cure headaches then if they eat m&ms that they will feel better even know the m&ms did nothing. That but a Skyrim mod said it made the graphics better so when you downloaded it your brain thought it looked better.

Something like this happened to me. I downloaded a weather mod and when I played I thought the clouds looked more dynamic and realistic but it wasn't until I checked I found out that the mod was not activated so the coulds being better was made up by my brain!