A meta-analytic cognitive framework of nudge and sludge

Abstract

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. A nudge is designed to facilitate actions by minimizing friction, while a sludge is an intervention that inhibits actions by increasing friction. While the terms nudge and sludge have garnered significant attention, the underlying cognitive mechanisms behind these interventions remain largely unknown. Here, we develop a novel cognitive framework by organizing 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) that contained real behavioral measures (n = 188 papers, k = 188 observations, N = 2,209,334 participants) from 2008 to 2021 to examine the effect size of these interventions targeting each cognitive process. Our findings demonstrate that interventions that change effort are more effective than interventions that change intrinsic motivation to alter behaviors. Nudge and sludge interventions had similar effect sizes. 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.