Scientists say that in virtually every case of being "head-over-heels" in love, what people love is usually not a specific person, but the pleasurable feeling she or he generates.
It is not the pretty or handsome face, it is not just the sweet voice or flashing eyes, there is body language, speed and rhythm of speech, touch, scent and pheromones, secreted chemicals that induce social reactions in others.
"What we first 'love' is the experience in our brain," according to Mao Lihua, associate professor of psychology in Peking University. The odourless pheromones are picked up by the nerve circuits in the brain, which trigger the pituitary gland hormone secretion. This causes the heart to beat faster, the breathing to quicken, the pulse to race, the blood flow to increase and ultimately cause sweaty palms and a dry mouth, reports Shanghai Daily.
All these reactions are sent back to the brain as clues and, the brain concludes, it must be love. The chemical cocktail includes adrenaline, oxytocin, dopamine, phenyl ethylamine, norepinephrine, endorphins, vasopressin, serotonin and testosterone.
"All the complicated processes are triggered swiftly and they work extremely fast and automatically," says psychologist Mao. "So all you can feel is that you are 'hit' - it's love at first sight."
Richard Zhu still remembers how fast his heart beat six years ago when a young woman with long hair and big, shiny eyes entered their French class. He stared at her and his palms became sweaty.
That was his first encounter with the woman who would later become his wife.
"I cannot say exactly which part of her is most attractive, but every moment around her makes me happy," says Zhu, now a university instructor in his early 30s.