Klusowski, J. & Lewis, J. Relative Increases Appear Larger in Percentage Terms. Manuscript invited for resubmission at Management Science.

Business managers and policymakers often need to use numbers to communicate magnitude. Yet, conveying the magnitude of large relative changes without desensitizing people to further increases can be challenging—due to diminishing sensitivity as numbers increase. In this research, we propose that expressing a relative increase in percentages can help convey its magnitude both effectively and discriminably compared to using multipliers or even absolute numbers. We posit that this effect occurs via three empirical phenomena. First, different scales have different ranges of normal values (e.g., 0% to 100% for percentages and 2 times to 200 times for multipliers). Second, people evaluate the magnitude of a value relative to the normal range on the corresponding scale, such that values outside of the normal range (e.g., 300%) appear larger than equivalent values within the normal range on an alternative scale (e.g., 3 times). Third, people are sensitive to differences between values outside of the normal range, such that they often perceive two values as more different when they are above the normal range (e.g., 300% vs. 600%) than when the same values are within the normal range on a different scale (e.g., 3 times vs. 6 times). Data scraped from the New York Times and seven online experiments support these insights. The effects do not seem to result from alternative explanations (e.g., lack of numeracy, scale expansion-contraction and the unit effect, or decision-by-sampling). We discuss implications for understanding people’s magnitude perceptions, communicating large numeric changes or differences, and boundary conditions for existing theories.

The study materials, data, and code are available upon request.

Klusowski, J. Small, D.A., &, Goldenberg, J. Even Number Preference in Quantity Selection. Manuscript invited for resubmission at Journal of Consumer Research.

We find that people choose even numbers more frequently than odd numbers when selecting quantities (e.g., choosing how many apples to buy for oneself at a store). Drawing on a mix of data—including the Kilts-Nielsen consumer panel data and Amazon Mechanical Turk survey data—we find evidence of this tendency in shopping decisions as well as a variety of other quantity selection contexts. We propose that this phenomenon occurs because even numbers are more accessible and complete than odd numbers. This extends previous research findings relating to round numbers (typically those ending in 0 and 5) and shows that arbitrary selection of certain numbers occurs at a more granular level. Moreover, unlike round numbers, we find that people do not intuit the disproportionate selection of even numbers. We discuss implications for understanding and influencing quantity selection.

The study materials, data, and code are available upon request, except the Kilts-Nielsen Consumer Panel Data and the Joint Analytics Team Data.

Milkman,  K.L., . . . Klusowski, J., . . .  Duckworth,  A.L.  (2021).   A  Mega-Study Approach to Applied Behavioral Science. Nature, 600(7889), 478-483.

Policy-makers are increasingly turning to behavioural science for insights about how to improve citizens’ decisions and outcomes. Typically, different scientists test different intervention ideas in different samples using different outcomes over different time intervals. The lack of comparability of such individual investigations limits their potential to inform policy. Here, to address this limitation and accelerate the pace of discovery, we introduce the megastudy—a massive field experiment in which the effects of many different interventions are compared in the same population on the same objectively measured outcome for the same duration. In a megastudy targeting physical exercise among 61,293 members of an American fitness chain, 30 scientists from 15 different US universities worked in small independent teams to design a total of 54 different four-week digital programmes (or interventions) encouraging exercise. We show that 45% of these interventions significantly increased weekly gym visits by 9% to 27%; the top-performing intervention offered microrewards for returning to the gym after a missed workout. Only 8% of interventions induced behaviour change that was significant and measurable after the four-week intervention. Conditioning on the 45% of interventions that increased exercise during the intervention, we detected carry-over effects that were proportionally similar to those measured in previous research. Forecasts by impartial judges failed to predict which interventions would be most effective, underscoring the value of testing many ideas at once and, therefore, the potential for megastudies to improve the evidentiary value of behavioural science.

Klusowski, J., Small, D.A., & Simmons, J.P. (2021). Does choice cause an illusion of control? Psychological Science , 32(2), 159-172.

Previous research suggests that choice causes an illusion of control—that it makes people feel more likely to achieve preferable outcomes, even when they are selecting among options that are functionally identical (e.g., lottery tickets with an identical chance of winning). This research has been widely accepted as evidence that choice can have significant welfare effects, even when it confers no actual control. ​In this article, we report the results of 17 experiments (N = 10,825 online/laboratory participants) examining whether choice truly causes an illusion of control. We find that choice rarely makes people feel more likely to achieve preferable outcomes—unless it makes the preferable outcomes actually more likely—and when it does, it is not because choice causes an illusion, but because choice reflects some participants’ pre-existing (illusory) beliefs that the functionally identical options are not identical.

The study materials, data, and code are available at the following link: https://osf.io/g2cbe/.