Martijn C. Willemsen
	E-mail:	M.C.Willemsen@tue.nl
	Current position:	assistant professor (UD)
	Phone:	x31 (0)40 247 2561
	Fax:	x31 (0)40 244 9875
	Office location:	IPO 0.17
	Address:	Dept. of Industrial Engineering and Innovation Sciences Group Human-Technology Interaction Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands

Introduction

Martijn Willemsen is assistant professor in the Department of Technology Management at the Eindhoven University of Technology. He holds a M.S. in Electrical Engineering and in Technology and Society from Eindhoven University of Technology and received a Ph.D. in psychology (decision making) at this University on April 25, 2002 for his dissertation, entitled: 'Explaining Asymmetries in Preference Elicitation: The Role of Negative Attributes in Judgment and Choice'.

From August 2003 - August 2004 Martijn was working as a visiting PostDoc at Columbia University with Prof. Eric Johnson on the application of process tracing methods on the internet. For this, they developed a process tracing tool called MouselabWEB, that allows process tracing on the internet, which can be found at: http://www.mouselabweb.org/. They are currently working together on several projects that purport to understand and model better the cognitive processes underlying several decision making phenomena, such as context effects, reference point effects and framing.

Research Interests

Main research interests are in field of decision making under certainty. Special attention is devoted to the role of positive and negative attribute values in any sort of evaluation task. Topics include differences between Choice and Matching, Joint versus Separate Evaluation and Scale issues. Most of this research is reported in Martijn's Ph.D. thesis. Currenlty, my interests extend to web applications and tools that support decision making.

Recommender systems
In this information overload society, many tools are available for helping people to make decisions among a multitude of options. These recommender systems employ smart algorithms that can predict how a person would like certain items, based on what he rated earlier, or what he watched (movies: netflix), listened to (last.fm), or bought before (amazon.com). Within our group, we study the psychological processes of decision making in these complex choice enviroments, focussing on how preferences should be represented in an algorithm, how we can prevent choice overload, and how we can enhance the usability of these systems. Currently, I am participating in the FP7 European project MyMedia.
Ons this project I am working together with Bart Knijnenburg, who graduated for his Master thesis in June 2009. Our first conference publication based on his thesis work won the best paper award on RecSys 2009.

Veni Grant: positive and negative descriptions and online reviews
From 2003 till 2006, a research program was executed (funded by a Veni-grant from NWO (Dutch Science Foundation)) that extended this research by investigating the way in which people describe choice options, in terms of positive and negative charaterizations. Within this project we investigated what type of descriptions people prefer to provide to others, prefer to receive themselves and what type they actually use in the decision process. Part of this research project looked into how people use online (customer) reviews in their decision making process while shopping online.

Cognitive processes: process tracing and modeling
Another research direction is the use of process tracing techniques to get more insight into the cognitive processes underlying decision making phenomena, which is joint work with Eric Johnson (Columbia) and Ulf Böckenholt (McGill University). The project 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). Currently a paper is published inPsycholological Review that uses this new approach in a comment to the Priority Heuristic.

Comprehension checks
Together with Gideon Keren, Martijn has been working on an paper that shows that comprehension checks are important when performing experiments. We shows that the uncertainty effect, as found by Gneezy, List and Wu (2006) might have been caused by miscomprehension. This paper is now published in JBDM.

Choice and Reject
Together with Gideon Keren, Martijn is working on a research program on choice and reject in binary choice between good and poor options, and the role of (anticipated) regret in choice versus reject.

Dissertation: Explaining Asymmetries in Preference Elicitation

Martijn Willemsen started his Ph.D. under supervision of Gideon Keren in february 1998. Related to his Master-thesis, a Ph.D. project was formulated on the topic of the measurement of subjective values: The problem of preference elicitation. Research in decision making has shown that measurements of preferences are sensitive to both the context and the method by which the preference is elicited.

Explaining Asymmetries in Preference Elicitation: The Role of Negative Attributes in Judgment and Choice The main focus of the project was on the asymmetrical role of negative (undesired) and positive (desired) attributes in choice and evaluation. Four methods of preference elicitation were studied in detail: choice, matching (making two options equally attractive), separate evaluation (rating of a single option) and joint evaluation (comparative ratings of two options). The thesis demonstrates that negative attributes loom more than positive attributes and that this negativity effect varies along different methods of elicitation. Negative attributes loom more in choice than in matching (Willemsen and Keren, 2002), and in separate than in joint evaluation (Willemsen and Keren, working paper). Within the thesis, the matching procedure was studied in more detail (Willemsen and Keren, accepted pending revision).

[click to download PDF version]

Web Experiments

Next to his scientific interests, Martijn has a work-related interest in designing and using web experiments. Besides the development of MouselabWEB, he is also working on an open source tool for participant administration and experiment management.

Publications

Papers

• Keren, G.B., Willemsen, M.C. (2009). Decision anomalies, experimenter assumptions, and participants' comprehension : revaluating the uncertainty effect. Journal of Behavioral Decision Making, 22(3), 301-317.
• 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
• Willemsen, M.C. & Keren, G. (2004). The role of negative features in joint and separate evaluation, Journal of Behavioral Decision making, 17, 313-329
• Willemsen, M.C. & Keren, G. (2003). The meaning of indifference in choice behavior: Asymmetries in adjustments embodied in matching, Organizational Behavior and Human Decision Processes, 90, 342-359
• Willemsen, M.C., & Keren, G. (2002). Negative-based prominence: The role of negative features in matching and choice. Organizational Behavior and Human Decision Processes, 88, 643-666
• Willemsen, M.C. (2002). Explaining asymmetries in preference elicitation: The role of negative attributes in judgment and choice. Ph.D.Dissertation. University of Technology, Eindhoven.[full text book - pdf]
• Ridder, H. de & Willemsen, M.C. (2000). Percentage scaling: a new method for evaluating multiply impaired images. Proceedings of SPIE, vol. 3959

Conference proceedings

• Knijnenburg, B.P., Willemsen, M.C. (2009). Understanding the effect of adaptive preference elicitation methods on user satisfaction of a recommender system. 3rd ACM Conference on Recommender Systems, RecSys'09, 23 October - 25 October 2009, New York, NY. (pp. 381-384). (Best short paper award RecSys 2009)

Invited presentations:

• The who and why of context dependent choice.
  ERIM research seminar, Rotterdam School of Management, Erasmus University, January 19, 2009
• Testing Cognitive models of context effects using process data
  Research group Marketing, Faculty of Business and Economics - KULeuven, March 2008
• Process Tracing for Dummies, Solutions for design, analysis and presentation using Reference Dependence as a case study
  INSEAD Business School , Fontainebleau , France , January 2006
• Process Tracing for Dummies: Solutions for design, analysis and presentation
  University of Amsterdam , Social Decision Making group, January 2006
• Process Tracing for Dummies: Solutions for design, analysis and presentation
  Tilburg University , Economic and Social Psychology, December 2005
• Negative-based prominence: The role of negative features in matching and choice
  SPUDM conference (organized by European Association of Decision Making), August 2001, Amsterdam

Conference presentations:

• Title: Information processes underlying the MPG-illusion
  Paper presented at 22th Biennial Conference on Subjective Probability, Utility and Decision Making (SPUDM), 23-27 August, 2009, Rovereto, Italy
• The Why and When of Context Effects
  Paper presented within the ACR symposium: "Beyond 2x2x2: Methodological Advances in Uncovering Consumer Decision Processes"
  Association for Consumer Research conference, October 23-26, 2008, San Francisco, CA
• Testing Cognitive models of context effects using process data
  Paper presented within the special session "Methodological Advances in Uncovering Consumer Decision Processes"
  37th European Marketing Academy (EMAC) conference, 27-30 May 2008, Brighton, UK
  
• Comprehension checks as a necessary condition for validating experimental demonstrations of normative violations.
  Paper presented at the 28th annual meeting of the Society for Judgment and Decision Making (JDM), Nov 16-19, 2007 , Long Beach, CA
• Consumer usage of positive and negative customer reviews in online decision making tasks
  Poster presented at the 28th annual meeting of the Society for Judgment and Decision Making (JDM), Nov 16-19, 2007 , Long Beach, CA
• Testing cognitive models of context effects using process data
  Paper presented at the 27th annual meeting of the Society for Judgment and Decision Making (JDM), Nov 17-20, 2006 , Houston, TX
• Process Tracing for Dummies: Solutions for design, analysis and presentation
  Paper presented at the 26th annual meeting of the Society for Judgment and Decision Making (JDM), Nov 11-14, 2005 , Toronto , Canada
• Choice and Reject Strategies in Binary Decision Problems
  Paper presented at 20th Biennial Conference on Subjective Probability, Utility and Decision Making (SPUDM), 22-24 August, 2005, Stockholm , Sweden .
• Do losses really loom larger than gains? A process perspective on loss aversion
  Paper presented at the 25th annual meeting of the Society for Judgment and Decision Making (JDM), Nov 19-22, 2004 , Minneapolis MN
• MouselabWEB: Process tracing anywhere, anytime!
  Paper presented at the annual meeting of the Society for Computers in Psychology (SCIP), Nov 18, 2004 , Minneapolis MN
• Do losses really loom larger than gains? A process perspective on loss aversion
  Paper presented at the 3rd Tilburg Symposium on Psychology and Economics: Games and Decisions, Tilburg (NL), Sept 1, 2004
• Loss Aversion Has Two Faces
  Paper presentation at the 9th Behavioral Decision Research in Management Conference (BDRM), April 15-18, 2004 , Duke University 's Fuqua School of Business, Durham , NC
• Asymmetric compatibility effects in choice and reject
  Poster presentation at the 24th annual meeting of the Society for Judgment and Decision Making (JDM), November 9-10, 2003 , Vancouver , BC Canada
• Positive/Negative asymmetries underlying matching and choice
  Paper presentation with Gideon Keren at the 23rd annual meeting of the Society for Judgment and Decision Making (JDM), November 24-25, 2002 , Kansas City , MO
• Advantage of A or disadvantage of B? Positive and negative facets in the description of choice options.
  Poster presentation at the 23rd annual meeting of the Society for Judgment and Decision Making (JDM), November 24-25, 2002, Kansas City, MO
• Differential weighing of attributes in joint and separate evaluation: the role of negative features.
  Paper presentation at the 8th Behavioral Decision Research in Management Conference (BDRM), May 31 - June 1, 2002 , Chicago
• The Good, the Bad, and the Ugly: Determinants of positive and negative features in choice
  Poster presentation at the 21st annual meeting of the Society for Judgment and Decision Making (JDM), November 18-20, 2000, New Orleans
• Predicting the prominent attribute: The role of negative features in matching and choice
  Poster presentation at the 20th annual meeting of the Society for Judgment and Decision Making (JDM), November 21-23, 1999 , Los Angeles