I'm sure we all remember a time when we fell in love. For some it was a gradual realisation that the person you knew was actually amazing. For others, it was love at first sight – an instant lightning-bolt moment that you knew you'd met your perfect match.

What is it that makes someone instantly love someone? Physical attraction is an obvious answer but there are other reasons that can create affection for someone; compatibility, personality and a good sense of humour to name just a few.

But according to one expert, there is a more scientific explanation. Dr Anna Machin, an Evolutionary Anthropologist at the University of Oxford says men look for signs of fertility and good health in a partner "and the major indicator of that in women is the waist-hip ratio… the absolute ideal." This is believed to be 0.7 which is "really your classic hourglass figure." And what do women look for in men? Well other experts have discovered they look for men who are taller, with broad shoulders and a relatively narrow waist – so a 'V' shaped torso.

If you're worried your figure isn't the perfect shape, there could be other factors that will cause someone to fall head over heels in love with you – people also use their sense of smell to sniff out their ideal mate. Apparently, we can detect whether people are genetically different to us by the way they smell.

Even if a potential partner's smell is a passion-killer, their facial expressions might make you infatuated with them. According to Professor David Perrett, at the School of Psychology and Neuroscience at St Andrews University, "we can change our faces by interacting with others and doing so in a pleasant manner, and that will aid our attractiveness and make others interested in us."

So it's good to know there are many reasons why we might be smitten with someone, but there is a problem; will the feeling be mutual and if it is, how long will it last? Nothing is guaranteed and, we know from Shakespeare, the course of true love never ran smoothly!
词汇表
fell in love 坠入爱河，相爱了
love at first sight 一见钟情
lightning-bolt moment 电闪雷鸣的一刻，突然间
perfect match 完美的另一半，天生绝配
physical attraction 身体、外表吸引力
affection 喜爱，爱慕之情
a good sense of humour 有很好的幽默感
waist-hip ratio 腰臀比
hourglass figure 蜂腰体形，沙漏形身材
torso 躯干，身躯
to fall head over heels in love 坠入爱河，爱得神魂颠倒
mate （名词）配偶
a passion-killer （俗语）激情杀手，令人丧失激情的事物
infatuated 迷恋的，着迷的
smitten 着了迷的，突然爱上的
mutual 相互的，彼此共同的
the course of true love never ran smoothly 真爱之路永远充满坎坷