Frowning?

Today my friend Shannin asked me to wrinkle my forehead, so I wrinkled my forehead. Then she asked me to frown, I did that too. She started laughing at me and I had no idea why! Turns out it was because I wrinkled my forehead and lowered my eyebrows to frown - not frowning in her book. Not frowning in her roommate's book either. Not frowning for my roommate either. They all said that frowning is a sad look or facial expression. I asked my friend Chad what :( means -- he said it means frowning. WHAT!?! Everyone was laughing not with me, but at me because I had been in the dark for almost 21 years about what frowning was/meant. I was staggered, shocked, incredulous. So then I did some research. According to Wikipedia, the most trusted source of information in the entire world....

A frown (also known as a scowl) is a facial expression used to indicate displeasure, or disapproval.

The appearance of a frown varies from culture to culture. Although most technical definitions define it as a wrinkling of the brow, in the USA it is primarily thought of as an expression of the mouth. In those cases when used iconically, as with an emoticon, it is entirely presented as a curve of the lips facing away from the eyes ('down').

It most commonly expresses sadness, dissatisfaction, anger, worry or pain.

OK then!! What I want to know is from what culture did I get this idea of lowering my eyebrows and wrinkling my forehead to frown? Obviously I cannot use this expression around my American friends... You never know when someone may ask you to frown!

So what do you think? Does frowning mean this: :-( or this >:-|