【Kevin éire 的回答】
观察他们的脚！
观察群体的成员怎么摆放他们的脚，往往能够识别出这群人的社交动态。
脚冲着群体外的方向——很可能意味着他正准备离开，或者在群体中感到很不舒服。后一种情况通常能被多余的小动作，或避免与群体成员有眼神接触所印证。
每只脚都指向群体中的不同成员——常发生在谈话中的群体成员都是朋友的情况下，如果根据脚指的方向画直线，你就能发觉这些线如何相交。它们通常有固定的模式，比如三个朋友构成一个三角形。
如果有什么人的脚和群体的相交方式不合理，那么很有可能这个人刚来的这个群体，或者因为某种原因无法被群体接受。
两只脚面对同一个人——这种情况格外地重要。通常意味着“我想要和你单独聊”，或“我对你说的话或正在做的事相当感兴趣”。你还可以看出是否他得到相同的反馈，也就是说看到另一方是否也有同样的动作。当然还有更明显的标志告诉你，这两个人是不是对彼此感兴趣。
虽然群体成员的双脚指向有太多种不同的组合，但是靠上面说的这几种足够你起步了。（你们吐槽我吧，我等会再接着说）
现在来看看其他几种情况。
行走的步调一致——两个人步速相同，步调一致，这通常是好基友的标志（或者代表着有人想破解肢体语言的秘密，比如像我这样的“变态”）
如果你看到一对情侣，而且其中一个分神了或很心烦，那你就会发现他们的步调变得不一致。如果接下来你看到他/她又找回状态了，比如说在逗另一个人开心，那么他们的步调很快又会变得一致。
脚动来动去——大多数人了解这一点。动脚有时意味着紧张或不舒服。特别提到这一点是为了提醒你们，别太相信这个——因为有人的裤子太刺挠。
（请参阅：如果一个人是因为鼻子痒才总挠它，千万别怀疑他做了什么亏心事。）
补充：很多情况下观察脚的方法并不管用。比如在拥挤的酒吧里，动作受到限制，那么双脚呈现出来的方位，或者说双脚动作的不协调就没有那么多的深意了。
以下为英文原文：
【Kevin éire 】
Watch their feet!
You can frequently tell the social dynamic of a group of people by seeing which way their feet are pointing.
Feet pointing away from the group - Probably means he's getting ready to leave or is feeling uncomfortable with the group. The latter case can normally be identified by fidgeting or avoiding eye contact with the group.
Each foot pointing to a different member of the group - This is common amongst groups of good friends in conversation, you can draw lines based on which way the feet are pointing and notice how they intersect. They usually make a regular pattern such as a triangle in the case of 3 friends.
If someone's feet don't intersect with the group in a logical way then it's likely they're new to the group or are not being as readily accepted for some reason
Both feet facing one person - Particularly significant in a group. Usually means "I want to speak to you on your own" or "I'm really interested in what you're saying or doing". You can see if it's being reciprocated if the person is mirroring the action though in this case there will often be more obvious indicators that the people are interested in each other.
There are tons of different combinations of feet facing but the above are enough to get your feet off the ground *pauses for readers to groan*
Lets look at a couple of other feet factors;
Walking with feet in line - Two people walking at the same pace with their feet in line is normally a sign of good rapport (or of a body language hacking sociopath such as myself).
If you see a couple and one becomes distracted or worried you can see the steps fall out of sync. If you then see one of the partners re-engage by making the other laugh for example then their steps will almost immediately fall back in sync.
Shifting of the feet - Most people know this one. Shifting your feet is sometimes a sign of unease or discomfort. I mention this specifically to tell you not to read too much into it - some people have itchy pants.
(See also: The man who has nothing to hide scratching his nose because it was itchy)
NOTE: The use of feet becomes almost unusable in many circumstances. If people are in a busy bar and are being cramped then the lines the feet display or the mismatching of movement of feet are less meaningful.
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