Study of the Use of Emoticons

Emoticons, those little confabulated piece of punctuation have been around for some time. Some people use little image-icons, though they have been around since ASCII text days. Are the effective? I use them mostly in non-professional communication, where I want to indicate humor, irony, sarcasm or other emotions that my face is not there to deliver. I have always felt that overuse gives the wrong impression. Here is a study of their use.