I was searching for a definition of nonverbal communication for a recent school assignment and couldn't find one. As I learned, academics disagree on a definition, in part as the term is applied to a vast array of human and animal phenomenon, encompassing everything from architecture to extra sensory perception and from dance to fashion. I think a useful definition is that nonverbal communication is communication that goes along with words but does not use words.
In face-to-face (F2F) encounters one may observe various nonverbals, such as facial expressions, gestures (e.g. waving, nodding, winking), haptics (e.g. touching, kissing, holding), involuntary sounds (e.g. coughing, gasping, yawning), paralanguage (e.g. non-words such as umm and eh, inflection, intonation, accent), posture, proxemics (e.g. personal space, seating position), and silence.
Considering the oft-heard report that found that in any F2F communication the majority of the message is communicated nonverbally, so it is important to consider this in online communication. Interpreting nonverbals adeptly can reveal emotion, deception, agreement, sensitivity, etc. thus giving us greater insight and depth into those we're communicating with.
Most of the research I found focused on nonverbal communication in F2F and not online (Wikipedia being the only exception). I'm sure there is research out there but it's buried deep in the academic walled garden - plowed under perhaps. This got me thinking of the various ways we can communicate nonverbally online as individuals (opposed to how websites communicate nonverbally, e.g. through design).
Virtual worlds or MMOG, by simulating real life mimic the use of real life nonverbals, such as facial expression (of avatar), proxemics, and gestures.
A VoIP call will have the same nonverbals as a telephone call, e.g. paralanguage and silence, except that with my connections and microphone/speaker set-up some subtleties of intonation and inflection can be lost and dramatic pauses can just be the connection crapping out.
For text-based online communication, nonverbals can be seen in the use of fonts, text embellishment (e.g. bolding, italics), letter case (e.g. BLOCK CAPS), punctuation (!!!), spacing, and emoticons. I'm sure I'm missing stuff, so please let me know of any others.
That said, there still isn't the same array or degree of nonverbals online. I was thinking about some of the problems I have encountered with email. Email is such a lean medium in that it doesn't offer much ability beyond those listed above to add clarity, emphasis, or depth to one's message. Plus being asynchronous, it doesn't give as much chance to clarify on the spot. I think we have all encountered emails that people inferred things we did not intend. Humour, particularly sarcasm, is really difficult in email.
What's the solution? It seems to me that people use sarcasm much less in emails nowadays than they used to. Emoticons were helpful, but it seems like the happy face and sad face are passé and the many others never caught enough to be widely understood. On a personal level, I take more time to compose and double-check my emails than I used to, so I can compensate for otherwise lacking tone.
To further complicate things, when interpreting nonverbal communication F2F or online one should be aware that there are cultural, context, and individual differences. So there's no easy solution for adding clear nonverbal communication offline or online.