A stakeholder decides which information to share during requirements elicitation. These decisions are made under uncertainty: stakeholders may not have precise, concrete, and complete information about their own expectations from, or about the environment of the system-To-be, they may misunderstand information which a requirements engineer gives them, and they may not have perfect knowledge about the various opportunities that the current technology may offer. Stakeholders' decision-making is therefore likely to involve the use of heuristics. Understanding if stakeholders do indeed use heuristics during requirements elicitation, and if so, then which ones, should help understand requirements elicitation better, and design methods which can stimulate positive heuristics (those which help elicit relevant requirements) and mitigate negative ones. This paper defines what an elicitation heuristic may be, and proposes a set of research questions under the form of a matrix for the theoretical and empirical study of elicitation heuristics.