Selfless in the aspect of showing appreciation. This is in contrast to someone who shows appreciation with the intent of getting something in return. AKA, using or playing someone.
Also, I wouldn't consider any chemical release in the brain to be simple, especially when considering the associated experience. Does love really have to be supernatural for it to be valuable?
I think when you are able to open yourself up, you'll find that how love works doesn't matter. Instead, allowing yourself to experience love will.