The fundamentals of eye tracking part 5: The importance of piloting.

The goal of this article is to demonstrate the importance of pilot studies in empirical eye-tracking research. First, we show what can go wrong when proper pilot experiments are omitted for all phases of an eye-tracking study, from testing an experiment, conducting the data collection, to building, revising, and interpreting the data analysis. Second, we describe a series of eye-tracking studies as a case study, and elaborate on all the pilot experiments that were conducted. We highlight what was learned from each pilot experiment when conceiving, designing, and conducting the research. Finally, we give practical advice for eye-tracking researchers on planning and conducting pilot experiments. This advice can be summarized as (1) take enough time, (2) be problem-oriented, (3) pilots are of an iterative nature, (4) many questions are empirical, and (5) apply the four-eyes principle. We envision that the present article helps early career researchers discover, and more established researchers rediscover, the utility of pilot experiments.