FOR a lecture course I teach at Brown University called “Love Stories,” we begin at the beginning, with love at first sight. To its detractors, love at first sight must be an illusion — the wrong term for what is simply infatuation, or a way to sugarcoat lust. If you find yourself smitten with someone you’ve only just met, you’ll question whether you should give the feeling so much weight. Psychologists and neuro-scientists have tried to find some answers. But I would argue that for the best guidance, don’t look there — look to Shakespeare. Sifting through the science Even in a class tailored to romantics, when I poll my students about whether they believe in love at first sight,…