A meta-analytic cognitive framework of nudge and sludge

Abstract

Public and private institutions worldwide have gained considerable traction in developing interventions to alter people’s behaviors in predictable ways without limiting the freedom of choice or significantly changing the incentive structure (Thaler & Sunstein, 2008). A nudge is defined as an intervention to facilitate actions by minimizing friction and removing impediments, while a sludge is defined as an intervention that inhibits actions by increasing friction. While the terms nudge and sludge have garnered significant attention in behavioral economics, psychology, and public policy, the underlying cognitive mechanisms behind these interventions and their impact on behavior change remain largely unknown. We develop a novel cognitive framework by classifying these interventions along six cognitive processes: attention, perception, memory, effort, intrinsic motivation, and extrinsic motivation. In addition, we conduct a meta-analysis of field experiments (i.e., randomized controlled trials) (n=179 papers, k=222 observations, N=4,440,011 participants) from 2008 to 2020 to examine the effect size of these interventions targeting each cognitive process. Our findings demonstrate that effort-reducing interventions (e.g., convenience) are more effective than intrinsic motivation interventions (e.g., commitment-making) to change behaviors. Interventions that reduce or increase friction had similar effect sizes, although there were considerably fewer sludge studies (k=44) conducted to date than nudge ones (k=178). This new meta-analytic framework provides cognitive principles for organizing nudge and sludge with corresponding behavioral impacts. The insights gained from this framework help inform the design and development of future interventions based on cognitive insights.

Using behavioral interventions to reduce single-use produce bags

“…Nudge interventions were overall more effective than sludge interventions in reducing produce bag use. This finding was consistent with the previous meta-analyses showing that interventions that eased decision making were the most effective in the environmental domain (Luo et al, 2021;Mertens et al, 2022). This suggests that behavioral strategies to reduce plastic waste should make the decision to not use produce bags easier rather than making the decision to use produce bags harder.…”

“…These behavioral interventions were motivated by a new cognitive framework that categorized behavioral interventions along six cognitive processes: attention, perception, memory, effort, intrinsic motivation, and extrinsic motivation (Luo et al, 2021). For example, an intervention targeting attention is highlighting the rising global temperature which was found to increase proclimate actions in liberal individuals (Luo & Zhao, 2019).…”

“…In addition to the six cognitive factors, the cognitive framework distinguished nudge interventions (i.e., those that reduce decision friction) and sludge interventions (i.e., those that increase decision friction), thus forming 12 categories of behavioral interventions (Luo et al, 2021;Mills, 2020;Sunstein, 2019). An example nudge intervention to reduce plastic waste is to provide a small financial incentive for recycling plastic bottles, and an example sludge intervention to reduce plastic waste is to impose a small fee for using plastic bags.…”

An audience segmentation approach to conservation messaging for transforming the exotic pet trade

“…Despite the widespread understanding that pro-environmental values do not often translate into sustainable behaviors (Blake, 1999;Kollmuss & Agyeman, 2002;Vigors, 2018), our study highlights their relevance for certain segments, particularly those at the opposite ends of the spectrum in terms of commitment to wildlife conservation (i.e., early adopters and laggards). Past research has demonstrated that environmental cues or nudges, such as defaults, can significantly influence human behavior, whereas value-based interventions are found to have much smaller effects (Arno & Thomas, 2016;Luo et al, 2021;Mertens et al, 2022). This may be because the majority of the population, such as those in the early and late majority segments, are inclined to take actions that are easy and convenient rather than being moved by strong values or convictions (Sunstein, 2016;Sunstein & Reisch, 2014).…”

Identity over nudges? Factors influencing decisions about participation in pro-environmental behaviors

“…However, a meta-analysis concluded that methods that reduce the psychological or physical effort needed to perform actions are the most effective in modifying behavior (Luo et al, 2021). Therefore, it is assumed that if the same nudges are tested on different behaviors, the efficacy of nudges will be partly determined by the perceived effortfulness and difficulty of the target behaviors.…”