Epistemic modality refers to the speaker’s/signer’s attitude towards a proposition, regarding how the speaker/signer evaluates the degree of probability of a statement (e.g. concerning a person or a situation). This assessment is based on the speaker’s/signer’s knowledge, personal attitude, and/or past experiences.
The current state of research on ÖGS concerning epistemic modality (i.e. the speaker’s/signer’s assessment) shows that epistemic modality can be expressed non-manually. Nonmanuals refers to different kinds of head and body movements (such as head nods and headshakes) as well as particular movements/positions of the eyebrows and the mouth. So far research on ÖGS has detected four different ways of expressing epistemic modality:

1. In order to assess a proposition as very likely, a statement can be accompanied by head nods performed in a convinced way.
2. In order to assess a proposition as unlikely, a statement can be accompanied by headshakes performed in a tentative way.
3. In order to evaluate a proposition in a deliberate, insecure, or doubtful way, a statement can be accompanied by body sways.
4. In order to express concern/worry about a proposition, a statement can be accompanied by trembling movements of the head.

The non-manual elements listed above can also be accompanied by other non-manual elements. Further studies will give more detailed insight.