Let’s briefly come back to the fundamentals of CMC compared to FtF (Face-to-Face Communication) before elaborating on self-disclosure.
Since its inception, there has been growing interest in computer-mediated communication (CMC) and its effects on interpersonal behaviors. However, the results do not voice the same conclusions, depending on the context or methodology . They can vary to absolute opposite results; some studies highlighted the impersonal, task-oriented and hostile characteristic of this form of communication; other studies highlighted the creation of warm personal relations with adjustments in interpersonal relations over time. However, the consensus agrees on higher self-dislosure.
Attributes of Face-to-Face Communication
Face-to-Face (FtF) is the richest form of communication and according to the Media Richness Theory  it has four attributes:
“i) the capacity for providing immediate feedback (synchronicity);
ii) the number of social cues (i.e. verbal, non-verbal, and visual) available;
iii) the ability to personalize individual messages;
iv) the ability to express ideas with natural language”. 
FtF allows communicators to get indications of meaning behind the words through non-verbal communication which weighs for “about two-thirds of all communication between two people or between one speaker and a group of listeners” . One cannot not communicate , whether it is through body language, facial expression, tone of voice or consistency of nonverbal and verbal communication.
Attributes of Computer-Mediated Communication
The opposite of the FtF communication medium, CMC is the lowest medium of communication in the social context. It carries no nonverbal visual or auditory cues and inhibits the nature of social context decoding that can lead to more equivocal exchanges, the feedback may be delayed and the most current cues are text-based. The latter could seem surprising as the technology allows live video feed, but, against all odds, this hasn’t been adopted and people prefer to communicate through text messages .
Drawing on those aspects and despite the absence of “rich” communication characteristics, studies demonstrated the advantages of CMC compared to FtF. Firstly, one get time to prepare and think about what will be sent. Secondly, one can concentrate on the content itself, with no concern for social appropriateness and one’s own nonverbal formalities or others nonverbal decoding. These attributes can enhance significantly verbal communication of individuals suffering from shyness or any other fear or reluctance of FtF interactions , foster relationship development, positive affect and well-being   , enhance connectedness and greater productivity  , and as a final result self-disclosure  .
Self-Disclosure on the Internet
What's experts' standpoint about CMC?
Rheingold claims that “the medium will, by its nature . . . be a place where people often end up revealing themselves far more intimately than they would be inclined to do without the intermediation of screens and pseudonyms ” .
In real life context  self-disclosure is characterized by breadth and depth; breadth refers to the amount of information revealed and depth to the degree of intimacy in the act of disclosing information.  In virtual worlds, as a matter of fact, interaction on the Internet needs a high level of disclosure, wider breadth and deeper depth, to reduce uncertainty. Indeed, the Uncertainty Reduction Theory  explains that during the interaction, people need information about the other party in order to reduce their uncertainty and increase predictability. Due to abovementioned characteristics of FtF, one can consider that uncertainty can be highly reduced by communication cues, including non-verbal ones which is less achievable in CMC. Precisely, this explains higher self-disclosure in CMC
Besides, this phenomenon has been observed in surveys conducted online, showing reductions in socially desirable responding, higher level of self-disclosure and an increased willingness to answer sensitive questions. 
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