I think it's because of the specific topic of the discussion, in some cases there might not be much controversy about the subject or the question is very specific that a concrete answer can be had without much input from others in the community. Replying to the comments can be a good way to increase participation, but the users have to be motivated and interested to do so.

I think that the level of participation in any interaction is in direct proportion to the self-interest of the individual. If viewers of our discussions on ResearchGate feel that they will gain by contributing, they will. As Andres says, many of the questions raised on the forum are very specific, and could be seen as 'closed', in that they demand an 'answer' rather than a discussion, thus bringing the need for interaction to an end. By posing 'open' questions that allow for debate we should be able to encourage asynchronous discussion.

There are some very interesting points made so far;

firstly that the students are more likely to participate if it is in their self interests. Open questions that require discussion instead of an answer will assist in promoting participation but how the students gain from posting a response is still relies on the teacher providing some external motivation.

secondly Andres mentions "controversy" and this is a good point because if there are a number of opposing beliefs about a topic there will tend to be more participation. This will increase further if the beliefs are very strong held by both sides, Unfortunately this can be restricted by the course materials that need to be taught at a particular point in the course. The benefits of English being the Lingua Franca and being taught in place of native languages may be more interesting and controversial than the benefits teaching morphemes to L2 students.

Should the students be punished for not participating? I have used the carrot and the stick method of increasing participation but have seen that on occasion students will post bland declarative statements just to fulfil the requirements of the grading system and have not engaged with the topic.

In the UK a popular buzz word is "Lifelong learning" the idea being that we should encourage students to learn for the pleasure of learning even after they leave formal education. Extrinsic motivation from grades should be replaced by intrinsic motivation from the satisfaction of knowledge.

My own interest is in the level of interaction generated by a discussion and this is the focus of my question.

Thank you Ambele this is a very interesting point, by posting a comment you move from "silent listener" to active participant. If I then ask you to clarify your comment would this encourage you to participate again? Would you feel more inclined to participate again if I praised your answer by directly referring to it or would you prefer I asked you a direct question?

In a classroom discussion it is possible for a student to sit and listen without contributing but the teacher still knows they are participating. In an online discussion if the student does not contribute then that student effectively does not exist. The point that Ambele Mtafya made about the students feeling that their "little opinion" is valued is valid. In a classroom it is easy to move students or indicate that other students should have their "turn" but online (asynchronous) discussions are more difficult to modify or control. Helping any particular student feel that their views are valued is easier and more immediate in a classroom but over the top praise in an online discussion can appear false or patronising when in fact that was not the intention.

In my experience there are a number of things to consider. For example, does the situation feel authentic? Is there a good reason for students to contribute to a discussion? Also what's in it for them? See https://www.researchgate.net/publication/232966422_Discussing_Ethical_Issues_in_School_Science_An_investigation_into_the_opportunities_to_practise_and_develop_arguments_offered_by_online_and_facetoface_discussions?ev=prf_pub for a discussion of student interaction in an online forum for discussion of ethical issues in science.

Article Discussing Ethical Issues in School Science: An investigatio...

I agree with the distinction Ambele is making, that there is a difference between an online class where the student needs to be motivated to participate in a discussion and the teacher needs a way to gauge student engagement, and a completely voluntary forum like ResearchGate. I will say that for ResearchGate and MOOCs that are more problem-driven (as opposed to discussion-driven) I typically do not post unless I think I have something new to add to the discussion.

My husband teaches a number of online courses, and one of the ways he helps students interact (besides having the sort of requirement Glenn posted above) is to divide them into small groups for discussion. In a small group (3-5 people) each participant feels more obligated to contribute and less intimidated to do so, and non-participation is easy to spot by the instructor/TA, who can possibly help get the passive student involved.