Individual choices can affect our environmental footprints. One choice that can be particularly effective is adopting a less meat-intensive diet. As many animal advocates know, plant-based alternatives tend to have a lower environmental impact than animal protein.

Certain strategies can be used to “nudge” people toward more desirable behaviors, such as  default interventions. This involves setting a particular choice as a default option, so people have to actively decide to choose another option if they don’t want it. A good example of this is organ donors, where signups can be increased by requiring people to opt out of being a donor, rather than opting in. Default interventions can also be used to nudge people towards more green energy sources.

In this study, researchers review the success of default interventions to decrease meat consumption and consider the factors that might make these interventions more likely to work. The researchers found 12 peer-reviewed studies that fit their criteria. As they admit, this is quite a small number of studies for a review, so the results should be interpreted cautiously. Studies all focused on using defaults to either nudge consumers toward meat-free options, or to decrease meat portion size in meals or products. 

As an example of promoting meat-free menus, one study told people registering for a conference that they would be provided with a vegetarian lunch buffet. Attendees were required to indicate if they would like a non-vegetarian option instead. They were compared to attendees in another condition, where the non-vegetarian option was the default. Across three conferences, this meat-free default significantly increased the number of people choosing vegetarian options from 2-13% up to 86-89%. 

As an example of promoting smaller meat portion sizes, researchers at a supermarket made the portion size default choice for meat sausages either 17% or 33% smaller compared to the largest option. This led to an overall reduction in the amount of meat sold by 13%.

For both meat-free menus and smaller portion sizes, the default interventions were consistently successful at lowering meat consumption, although sometimes these effects were quite small. Furthermore, one of the studies included in this review was designed to answer why these interventions work. The authors note that there are several different underlying mechanisms that could be at play:

• Effort: Choosing a meat-free default is less work than choosing to switch to the alternative.
• Endorsement: If people are presented with a meat-free default, they might assume that this choice is in their best interest. They might also think there’s a social expectation to choose it. 
• Endowment: People may begin to feel a sense of attachment over the default option they’re given and compare alternative options to it.

By analyzing the studies in their data, the researchers considered which of these factors might make people more likely to stick with a meat-free default. 

In terms of effort, studies varied in important ways. Some studies used “default rules,” where people who didn’t make any active choice received the meat-free default. Others had “default options,” where people still needed to actively make a decision either way. Most studies used default options, which would mean it’s not much more work to opt for a meat option. The amount of attention a person is giving to the option probably also influences how likely they are to switch from the default.

The effect of endorsement can be looked at by comparing how recognizable the alternative is made, compared to the default. This review found that meat-free defaults were more likely to be a success if the alternative was less recognizable — for example, if less information was presented on the meat option. This might make the vegetarian option seem like it’s the recommended choice. Wording will also have an effect. If the alternative is made to sound abnormal, like in the case of the conference buffet option, it might not seem as appealing as the default. 

Endowment was perhaps less likely to have played a role in the studies used for this review. People in most studies still had to make a choice, so they might not feel so attached to the meat-free option. Also, many people have pre-existing, positive attachment toward options that contain meat.

While the use of meat-free or smaller meat portion defaults does appear to be effective, we don’t know how their effects might persist over time. Unlike opting to be an organ donor or choosing a green energy source, choosing food is not a long-term decision and might only be useful when selecting individual meals. Furthermore, it’s unclear whether green nudges make people reflect on why they’ve made a decision, so they’re not more likely to make it again in the future.

The researchers end by noting that these findings could be applied to policy, when trying to nudge people to eat less meat. However, it’s important that interventions be used in an ethical and responsible way. Specifically, it could be questionable to try and change people’s behavior without their conscious approval. For advocates interested in nudges, it’s important that the use of default interventions is made clear to consumers, and that they have the freedom to make their own choices without fear of costs if they don’t go for the desired option.