Martijn Willemsen The process tracing LAB of Martijn Willemsen researches how decisions can be better understood by using process tracing technologies such as Mouselab, mousetracking or eye-tracking to capture and analyze in detail information processing of decision makers.


The Process Tracing lab of Martijn Willemsen has developed and uses a number of different process tracing techniques, such as MouselabWEB, mouse-tracking and eye-tracking. The LAB tries to get deeper insight into the cognitive processes underlying the decision making process by analysing and modeling process data using modern techniques for data representation (Icon Graphs) and statistical analysis (multi-level modeling).

MouselabWEB, an online process tracing tool

Mouselab was developed in the eighties as a tool to capture information acquisition processes of decision makers using an information board technology. Information is hidden behind boxes and the decision maker acquires information by hovering the mouse over the box. Mouselab captures a lot of the cognitive processes as decision makers typically do not memorize the information, but use the display to compare attributes of the decision problem.

Together with Eric Johnson of Columbia University, Martijn Willemsen developed mouselabWEB, an online version of this process tracing tool that allows for larger and more heterogeneous samples as it can used in online surveys. Research has investigated the underlying processes of the Priority Heuristic (Schulte_Mecklenbeck et al., 2008) and Loss Aversion (Willemsen et al., 2011) and in context effects (Willemsen and Johnson, 2017 under review).

Relevant research papers and chapters:

  • Willemsen, M.C., Böckenholt, U. & Johnson, E.J. (2011). Choice by value encoding and value construction : processes of loss aversion. Journal of Experimental Psychology. General vol. 140, no. 3, p. 303-324,
  • Willemsen, M.C. & Johnson, E.J. (2011). Visiting the decision factory : observing cognition with MouselabWEB and other information acquisition methods. In M Schulte-Mecklenbeck, A. Kühberger & R. Ranyard (Eds.), A handbook of process tracing methods for decision research : a critical review and user’s guide. (pp. 19-42) New York: Psychology Press.
  • Johnson, E.J., Schulte-Mecklenbeck, M., & Willemsen, M.C. (2008). Process models deserve process data: Comment on Brandstätter, Gigerenzer, and Hertwig (2006), Psychological Review, 115, 263-272
  • Johnson, E.J., Schulte-Mecklenbeck, M., & Willemsen, M.C. (2008). Postscript: Rejoinder to Brandstätter, Gigerenzer, and Hertwig (2008), Psychological Review, 115, 272-273

Mouse-tracking and eye-tracking

Recent research with Chao Zhang in our lab includes using mouse-tracking on a tablet to investigate when users have difficulty choosing food items, which would allow us to test when users are most sensitive to nudges to choose a more healthy food items.

In May 2017 we started a research project on privacy decision making in IoT (Internet of Things) as part of the NWO/NSF PRICE call. This is joint work with Bart Knijnenburg (Clemson University) and Alfred Kobsa (UCI). At TU/e, Kevin Sun works as a PostDoc on investigating the processes behind privacy decision making, for which we will develop process tracing methods such as mouselabWEB and Eye-tracking. Very recently we acquired several Tobii 4c eye-trackers with research licenses and we are currently installing an eye-tracking lab and are developing the tools to measure the decision processes underlying privacy decision making.