You may not know who Albert Mehrabian, PhD, is, but you should at least be familiar with his work on communication. If anything, it can help you with your social interactions, though I also see its value in professional interactions, namely those that you have daily with your patients and other health care professionals. 
 
Dr. Mehrabian had 2 fundamental conclusions. First, that there are basically 3 elements in any face-to-face communication: words, tone of voice and nonverbal behavior (eg, facial expression). Second, that nonverbal elements are particularly important for communicating feelings and attitude, especially when they are incongruent. In other words, if your words do not agree with your tone of voice and nonverbal behavior (eg, body language), then people will be more likely to believe the tonality and nonverbal behavior.
 
While the words you choose to use when counseling a patient are very important, you must also be conscious of your tonality and nonverbal cues that convey your attitude towards the person and may influence his or her beliefs or convictions about you as a person, as well as a professional. Becoming more aware of these nonverbal cues can help you in your daily interactions, such as supporting your credibility as a health care professional in the eyes of the patient you just counseled, the physician you just spoke to, or the potential boss you had an interview with.
 
When you become more cognizant of the subtle ways in which you communicate nonverbally, you can use those signs and signals to communicate more effectively in all of your interactions.
 
There are general signs that indicate whether a person is feeling confident or fearful. Knowing the difference between them can help you answer the following questions:
  • Does this patient understand what I am explaining?
  • Does this physician agree with my clinical recommendation?
  • How did I do in this job interview?
While cultures and customs differ throughout the world, Americans typically respond positively and express confidence in the following nonverbal ways:

Posture 
They stand tall with their shoulders back, as opposed to slouching.  I maintain a body position that faces the person (in a non-threatening way) to make sure that I am not facing away from the person with my body unaligned with theirs.

Eye contact 
They maintain solid eye contact with a “smiling” face. This does not mean you should have a huge grin on your face for the duration of the entire interaction! Note that in certain Asian cultures, strong eye contact may be disrespectful.

Face, hand, and arm gestures
Your gestures should be purposeful and deliberate. It’s a fascinating aspect of human culture, but different hand gestures can mean completely different things around the world. Case in point: certain innocuous gestures may actually be offensive to some!
 
Speech/tone of voice 
They speak clearly and loud enough to be heard. That said, make sure that your vocal tone is not too loud or too soft. 
 
Some customary signs that the person you are speaking with is responding negatively, feeling defensive, or not being engaged in the conversation include:
  • Hands and arms are kept close to the body. Arms may be crossed in front of body, which is a very defensive position. Gestures are infrequent.
  • Hands may be picking at clothes or fiddling with pens.
  • Facial expressions are kept to a minimum.
  • Little to no eye contact. Eyes are downcast or gazing at something else.
  • Head is down.
  • Body is physically turned away from you.
  • The person may be sitting slumped in his or her chair.

The ultimate purpose of any interaction is to exchange information. You want to express that the person’s message is important to you and that his or her point is well received. 
 
Some signs that indicate a person is indeed thinking over your conveyed message include:
  • Eyes look away (perhaps to think) and return to engage when answering
  • Finger is stroking chin
  • Hand touches cheek
  • Head is tilted with eyes looking up. This means that the person is probably making pictures in their head and thus may be an indicator of a visual thinker. It may also mean that they are recalling their prepared words.
Body language and nonverbal cues can tell you when your patient or colleague has a question, wants to say something, agrees or disagrees with you, needs a break, requires more explanation, or has an emotional response. Nonverbal behavior includes body movements, gestures, posture, eye contact, and the tonality and quality of speech.
 
It is also important to understand that body language may vary greatly between individuals, cultures, and nationalities. Therefore, it is essential to verify and confirm the signals that you are reading by getting to know the person. Using these techniques will make a significant and positive impact on your patient care and therapeutic outcomes through effective counseling.