There exists a book called What Every BODY is Saying, which documents an ex-FBI envestigator who specialized in non-verbal communication explaining various body language cues and how to notice and interpret them in day-to-day life.

He covers the feet and legs in great detail. Here is a succinct summary of the information and some examples in RP context.

When we think about body language, we almost always think about the face or hands. This works and all, but someone's feet can tell you so much more.

Why is below our waist so honest?

Our feet are very good indicators of intention, and always have been. Since before humans could even vocalize words to describe scenarios, visual cues taken from the point of someone's feet have always told the situation of what's going on. Whether they suddenly stop moving in the face of danger, or whether they begin moving in response to stimulus.

Crossed/Uncrossed Legs

When a person crosses their legs, they are doing one of two things.

  • Providing a barrier to uncomfort in a situation they can not escape

  • Indicating comfort and intent to remain in a situation they can escape

This may sound like it sucks that it can mean two entirely different things, but in context with situations, it is actually fairly easy to tell when the intent is one or the other.

Crossing the legs is a counter-intuitive action in evolution, as it restricts our ability to use our legs. This is why it is typically only done to express extreme comfort with someone, as our body is willingly limiting itself to display this to another.

Direction of Feet

When someone's feet are firmly placed on the ground, the direction they have chosen to angle their feet can tell you a lot about their intentions.

If someone is intent on talking to the person they are engaged with, they will stand confidently and have both feet facing the person they are talking to. As a conversation drags on, or if a person is interacting with someone they have no desire to, you will notice one or both feet pointing away, towards exit. It may not be THE exit to the location, but typically a person's subconscious will direct one or both of their feet towards what their intent is, and the magnitude of this variance from the conversation can tell you about a person's general interest or time/ability to have a conversation at that moment.

This does not mean they do not want to talk to whoever they are with, it may mean they have a meeting to make or it's about time for them to leave. On the other hand, a sudden change in direction of feet while mid-conversation can tell you loads about where their subconscious has shifted its attention.

Movement/Jitters

Rapid movement in the feet or legs, when up or down, is a really good indicator of excitement and/or anxiousness, You want to progress to the thing you know is coming, and your legs have begun reacting to this idea preemptively.

This could be excitement for a class to end, anxiousness to be done during an interview, or a girl showing subconscious interest at the prospect of an idea you just brought up. The key here is, again, looking for changes in this behaviour.

  • A girl sitting alone at a bar shaking her feet in her chair and looking at her phone is probably just waiting for the Uber.

  • A girl who begins subtly shaking her leg after you mention going back to your place to try out that pasta recipe you were talking about, is probably interested in going back with you.

Curling/Raising

In his book, Navarro details what he calls "Gravity defying moments". I like to think of this as more of a 'curling' of muscles, such as feet.

When a person reaches orgasm, it is common knowledge that feet will generally contract or extend, pointedly. The feet also do this sort of thing in day-to-day life.

When someone is content or happy, a subtle but noticeable effect is that they may raise their toes towards the sky. You may not think much of this, but a change from flat footed to raised up toes may indicate that something pleasant has entered the thoughts of the person exhibiting this behaviour, and it is up to you to figure out what that was, in context.

The reverse of this is feet pointed down. Imagine someone sitting in a meeting room, on the edge of their seat ready to leave. You probably already imagined their toes on the ground, and heels raised, ready to move as soon as they are permitted. This is your body signifying that something is less than pleasant, and expressing a desire to escape the situation at the earliest convenience

These are just a few examples of what just the feet can tell you about a situation, or group of people. By analyzing current positions of lower limbs, and noting changes in such, you will find yourself to be able to more aptly notice people's intentions of action, and how comfortable they are in the current location or situation.