Signed languages employ finely articulated facial and head displays to express grammatical meanings such as mood and modality, complex propositions, information structure, assertions, content and yes/no questions, imperatives, and miratives. In this paper we examine two facial displays: an upper face display in which the eyebrows are pulled together called brow furrow, and a lower face display in which the corners of the mouth are turned down into a distinctive configuration that resembles a frown or upside-down U-shape. Our analysis employs (...) Cognitive Grammar, specifically the control cycle and its manifestation in effective control and epistemic control. Our claim is that effective and epistemic control are associated with embodied actions. Prototypical physical effective control requires effortful activity and the forceful exertion of energy and is commonly correlated with upper face activity, often called the “face of effort.” The lower face display has been shown to be associated with epistemic indetermination, uncertainty, doubt, obviousness, and skepticism. We demonstrate that the control cycle unifies the diverse grammatical functions expressed by each facial display within a language, and that they express similar functions across a wide range of signed languages. (shrink)