[Context and motivation] i* is one of the most popular modelling languages in Requirements Engineering. i* models are meant to support communication between technical and non-technical stakeholders about the goals of the future system. Recent research has established that the effectiveness of model-mediated communication heavily depends on the visual syntax of the modelling language. A number of flaws in the visual syntax of i* have been uncovered and possible improvements have been suggested. [Question/problem] Producing effective visual notations is a complex task that requires taking into account various interacting quality criteria. In this paper, we focus on one of those criteria: Semantic Transparency, that is, the ability of notation symbols to suggest their meaning. [Principal ideas/results] Complementarily to previous research, we take an empirical approach. We give a preview of a series of experiments designed to identify a new symbol set for i* and to evaluate its semantic transparency. [Contribution] The reported work is an important milestone on the path towards cognitively effective requirements modelling notations. Although it does not solve all the problems in the i* notation, it illustrates the usefulness of an empirical approach to visual syntax definition. This approach can later be transposed to other quality criteria and other notations.