Body language, facial expressions and voice give people an idea of who we are. If we deprive this information, we risk to create a wrong impression.

A person who does not send any non-verbal signals, may be perceived by others as hard or uninterested in the work.
This does not mean that already at the first meeting with the employer need to show him their full range of non-verbal features. For a positive assessment of quite a bit to prove himself. So, during the interview, you can use a short handshake, a smile, eye contact and a nod. A moderate amount of gestures to enhance the expressiveness of speech is also appropriate.
By the way, it turned out that during the interview non-verbal cues are especially important for women. In their case, a firm handshake is able to make a better impression than a long and detailed account of the past achievements.