As with discussing God, or free will, or freedom, in discussions of love I think some initial definitions can help.
I think a lot of us (although not necessarily all of us) would distinguish between a case of the hots for someone and falling in love with them.
On the other hand, many of us (probably most of us, in here) would agree that chemistry, hormones, neurotransmitters responding to some biological imperatives do play a role in what we call “love”.
After all, I love my Dad, loved our kitty cat, I love my country (in a wry and critical and disappointed way, but still), I love myself, I love the other members of my species (some wry and critical stuff going on there too), I love saffron rice and the best of Pink Floyd and the color combo of prize-ribbon blue and rusty red… but we all know that when we’re speaking of falling in love it’s a different and distinct phenomenon than these other things.
And this one type of love is of sufficient importance that if someone asks about love without elaboration we assume it’s romantic love they’re talking about and not their love of nature or whatever. So it’s a big fucking deal for us.
Love of this sort is not the same as a fundamental assessment of another person that finds them to be an incredible and wonderful person with lots of great qualities. It’s not even the same as finding one’s own self to be in awe-filled and joyful appreciation of that wonderful person’s qualities. That can certainly coexist, but this latter kind of love really IS the kind that you can also feel for your child, your Aunt Ellen, or your best friend, and it isn’t romantic love.
So with all that being said (and to which you can of course dissent), no I don’t believe in love at first sight:
• It takes longer to learn enough about the other person and develop a sense of them;
• It also takes longer for your neurochemistry to react to the inputs of what interacting with this person feels like
• It’s neither an assessment of the other person’s overall goodness nor an evaluation of their visual (and other-sensory) hotness, but it involves both of those plus a bunch of other stuff, a cocktail of elements to be interpreted and reacted to, and it just doesn’t happen instantaneously.