Why plain language works better than cash to drive sustainability

Consumers often express positive views toward environmentally friendly actions like recycling, but good intentions don’t always translate into actual behavior. One possible reason? Consumers find it challenging to gauge how much of a positive environmental impact they’re having.

A study conducted by MIT Sloan School of Management professor Catherine Tucker and colleagues shows that clear, jargon-free language gets people to recycle, even more so than financial incentives do. 

The researchers conducted a large, randomized field experiment from June 1 to Aug. 31, 2023, of more than 380,000 households in China, testing two strategies to increase recycling: simplifying scientific jargon or offering small monetary incentives.

They found that simplifying the language they used when communicating with households increased recycling behavior more than monetary incentives did. Interestingly, combining both strategies was less effective than using either approach alone. 

Messaging makes a difference

The recycling company involved in the study normally provides customers with a statement describing their recycling achievements in terms of CO₂ emissions. 

In structuring their study, the researchers divided participants into four groups: 

• Group 1 (control group): Customers received the same message they had been receiving all along: “You have recycled x kilograms of recyclables, reducing y kilograms of CO2 emissions.”
• Group 2: Customers received a message tied to a specific outcome: “You have recycled x kilograms of recyclables, equivalent to z kilometers of reduced driving.”
• Group 3: Customers received a message focused on rewards (“You have recycled x kilograms of recyclables, reducing y kilograms of CO₂ emissions”) and were enrolled in a milestone monetary rewards program. 
• Group 4: Customers received a less-jargony version of Group 3’s message and were also offered milestone rewards.

What researchers learned about sustainability messaging

1. Reducing jargon significantly increased recycling. Using a more familiar sustainability metric — number of kilometers of driving reduced — in place of standard measures of carbon emissions raised the recyclable weight per household by 2.2%, “a substantial improvement considering the typical inherent constraints on household recyclable output,”the researchers write. This option was low cost and provided a measurement that was both quantifiable and relatable, they write.
2. Monetary incentives also worked, but at a cost. To see whether monetary incentives had any impact, the researchers set small monetary incentives that participants would receive upon reaching different, specified levels of recycling activity, which were indicated by a badge on their mobile apps. This method increased recycling by 1.9%. 
   
   However, “while monetary incentives also promote household recycling behavior, they are more costly to administer and do not outperform improved comprehension,” the researchers write. 
3. Combining interventions was less effective. Using simplified messaging and monetary incentives together was less effective at increasing recycling than using each method on its own, possibly because the combination triggered competing motivations for customers. Using both interventions resulted in a 1.2% rise in recycling. 

“Taken together, the results suggest a sequencing strategy: Prioritize improving comprehension through jargon reduction in the near term, followed by targeted use of incentives or penalties once understanding is established,” the researchers write.

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Lessons for sustainability messaging

Unlike monetary incentives, simplified messaging requires no ongoing financial outlay, making it one of the more scalable tools available to policymakers and platform designers, the researchers write. “Our proposed solution is both easy to implement and cost-efficient from a policy perspective.”

The implications of this study are relevant to companies in different sectors. Businesses could benefit from simplifying their language when communicating their sustainability initiatives — specifically, by stating their sustainability goals in something other than carbon measurement units. 

Many online travel sites provide information on carbon emissions associated with a passenger’s travel route in kilograms of CO₂, but travelers may find it hard to understand the relevance of a 10-kilogram reduction in CO₂ emissions, the researchers write. And prior research about food packaging has shown that consumers appear to react more strongly to an “organic” label than to a label about the food’s carbon footprint. 

“We show that even when presented with accurate carbon emissions, consumers react less strongly to them than something more familiar,” the researchers write. 

“Optimizing Sustainable Choices: Evidence From a Large-Scale Randomized Field Experiment on Household Recycling” was authored by Tucker, Linyi Li of Singapore Management University, Rui Yan of the University of Science and Technology Beijing, and Rowan Wang of the Southern University of Science and Technology.

Catherine Tucker is a professor of marketing at MIT Sloan, faculty director of the school’s Executive MBA program, and a co-founder of the MIT Cryptoeconomics Lab. Her research focuses on the interface between marketing, the economics of technology, and law, with an emphasis in online advertising, digital health, social media, and electronic privacy. Her recent work includes an exploration of generative AI and weight loss and the ways global platform governance relates to digital apps for children.