Ask any random collection of strangers what they look for in a friend, and odds are you'll get pretty similar answers across the board: someone who's fun to be around. Someone who shares your sense of humor. Someone you can trust.
隨便問一群陌生人，他們在交友時都看中什麼,得到的答案一定極其相似：相處時能給你帶來快樂的人、能夠欣賞你的幽默感的人、你能信任的人。
But often, friendship begins long before any of those things can come to light in any meaningful way. According to one survey, around 60 percent of men and half of women believe in love at first sight; at least that many, I'd wager, have experienced that moment when you meet someone new and feel the friendship blooming in your gut — you just understand, instinctively, that a bond is about to form.
不過，通常友情早在人們意識到這些之前就已經開始了。一項研究顯示，約60%的男性和50%的女性相信一見鍾情；並且我敢打賭，有許多人已經經歷過這樣的時刻：當你結識新朋友，感覺到友誼開始在你們的體內流動——你們即將締結友情的契約。
Call it a spark, call it chemistry, call it friendship at first sight; whatever it is, it can happen in just a small handful of seconds, which is the amount of time we need to form a first impression of someone (if that — one study suggests that we make our judgments just a tenth of a second after seeing a face).
無論你稱之為燃起火花、發生化學反應，還是一見鍾情的友誼，它只在幾秒鐘內就發生了。這就是我們對一個人形成第一印象的時間（正如一項研究表明，在我們看到他人後，十分之一秒便已經作出了判斷）。
In a study published in Nature in 2009, researchers identified two areas of the brain that become especially active when we meet someone new: the amygdala, the area of the brain that deals with emotion, and the posterior cingulate cortex, which is linked to autobiographical memory. As Karla Starr noted in Psychology Today, the posterior cingulate cortex also helps us weigh decisions and assign value to objects; we go through a very similar process with humans. "And after we've assigned a value to a person, we make the decision about how to orient ourselves to that person," she wrote. "Do we want to get closer? Knowing what this person's value is to us, do we want this person to be involved in our network?"
在2009年發表在《自然》雜誌上的一項調查中，研究人員發現，在我們遇到陌生人時，大腦中的兩個區域變得異常活躍：杏仁體，即大腦中處理情感的區域，以及後扣帶回，與自體的記憶有關。正如卡拉. 斯塔爾在雜誌《今日心理學》中所指出的，後扣帶回同樣幫助我們權衡決策以及為對象分配價值，我們人類經歷了一個非常類似的過程。“當我們為一個人分配了價值後，我們決定自己將如何與那個人相處，”她這樣寫道，“我們想要變得親近嗎？知道某個人的價值後，我們是否想讓這個人加入我的社交圈呢？”
The answer is actually a compilation of several smaller judgments, explains Kelly Campbell, a psychology professor at California State University, San Bernardino. "What are the things we care about in a friend? We care about someone who's going to be fun, that we can enjoy ourselves with … You need emotional support, social support, you want then to be loyal and trustworthy, you don't want to feel judged," she says. "When you first see the person, you don't realize how many judgments you're making, but you’re actually gathering information that's telling you if this person fills those needs for you."
這個問題的答案實際上是幾個小判斷共同編譯而成的，來自於聖博娜迪諾加州州立大學的一位心理學教授凱利.凱貝爾這樣解釋。“對於朋友，我們關心是事情是什麼呢？我們關心的是這個人需要很有趣，這樣在相處的過程中我們都很享受……你需要感情的支持，社會的支持，你希望他們是忠誠可靠的，你不想感覺被他人審視，”她這樣說，“當你第一眼看到一個人，你不知道你在做多少的判斷，但實際上你正在收集的信息會告訴你這個人是否能夠填補你的那些需求。”
Last year, Campbell headed up a study in The Social Science Journal on "friendship chemistry," which she and her colleagues defined as "an instant connection between friends that is easy and makes the relationship seem natural." (Friendship chemistry, Campbell noted, is one subset of "interpersonal chemistry," which includes romantic relationships.) The phenomenon wasn't always mutual, they found, but it seemed to strike certain groups more than others: Those who scored higher on the personality traits of agreeableness, openness, and conscientiousness, for example, were more likely to say that they'd experienced friendship chemistry.
去年，坎貝爾在《社會科學》雜誌上發表了一項名為“友誼化學”的研究，她和她的同事將此定義為“與朋友之間發生瞬時聯繫是輕而易舉的，並且這能使我們之間的關係顯得更加自然。”（坎貝爾指出，友誼化學是“人際化學”的一個子集，除此之外還包括戀愛關係。）他們發現，這個現象並不總是相互的，但這看起來更能打動指定的群體：例如，那些有親和力、開朗以及責任心等個性的人，往往能獲得較高的印象分的，更有可能經歷過友誼化學。