Pulses quicken when we're with a crush.
David Trood/Getty Images
Why do literature and art always associate romance and the heart? Because our hearts are set aflutter, pulses literally racing, at the sight of someone attractive [source: Fisher]. In fact, the heart-attraction relationship is so potent, studies have found that increasing someone's heart rate and then putting him or her near a pretty stranger can artificially ignite a flame of affection [source: Foster et al].
Per usual, the brain is ultimately responsible for this physiological response, not Cupid and his archery acumen. During early-stage romantic love -- scientific terminology for the honeymoon phase -- the brain releases norepinephrine whenever we're around a love interest to shake us into action [source: Obringer]. That adrenaline-like neurotransmitter spurs our motivational decision-making, possibly prodding us to chat up Mr. or Ms. Right. Meanwhile, our adrenaline-addled hearts are likely pumping faster than usual in order to get us through the taxing ordeal [source: Landau].
