Can Bonus Packs Mislead Consumers? An Empirical Assessment of the ECJ's Mars Judgment and its Potential Impact on EU Marketing Regulation

The use of psychological findings in EU internal market regulation has gained interest, particularly in the area of unfair commercial practices. This study investigates consumer perceptions of bonus packs containing an oversized indication of the 'extra' volume in the package (indication of 10% extra on a colored area that is considerably larger, such as in the Mars case). Results of our experiment show that consumers overestimate the extra volume when confronted with an oversized indication compared to control conditions, which can be considered empirical evidence that this practice is potentially misleading. Given that the perception of the internal market concept has changed since the Lisbon agenda, this type of scientific evidence is getting increasingly relevant. This study serves as a first indication that once a bias has been proven to be robust in several situational studies from behavioral sciences, regulators at EU level can base their regulatory decision on the existence of such a bias in similar cases