Note: In keeping with our commitments made in 2016, we have completed a reanalysis of the data and the conclusions originally reported in this blog post and its accompanying report. The full report on our reanalysis, Which Request Creates the Most Diet Change: A Reanalysis, covers both quantitative and inferential claims as well as an assessment of the methodology. The code used in our reanalysis is included in the report and may also be downloaded from the GitLab account of Humane League Labs.
Our reanalysis did not detect any significant differences between the vegan, vegetarian, less meat, combination or control groups on any of the measured changes in diet. Further, the study was insufficiently powered for us to place any confidence in the alternative claim that the messages are equally effective.
— Humane League Labs [November 13, 2017]
Posted on September 20, 2015; Last updated on November 4, 2015
Many vegan advocacy organizations realize that while their ideal is for everyone to go vegan, focusing on vegan eating in their advocacy materials may or may not create the most diet change. Is it better to promote vegan eating or vegetarian eating? Might it be even better to promote meat reduction, or to use a combination message of “cut out or cut back on” meat and other animal products? Each phrasing has its pros and cons, and to date no specific research had been done to test which phrasing works best in advocacy materials.
In this study, college students were approached at random on campus and asked to complete a short survey on how often they consume various animal products. They were then given a booklet that promoted veg eating. Booklets were identical to each other except for the type of diet change that was encouraged. Some booklets encouraged “vegan” eating, some encouraged “vegetarian” eating, some encouraged readers to “eat less meat,” and some encouraged readers to “cut out or cut back on” meat and other animal products. A control group was given no booklet.
Two to four months later, participants were followed up with by email and phone and asked to complete a new survey on how frequently they consumed various animal products.
A total of 1,594 participants aged 18 and up completed the initial survey, of which 601 participants completed the follow-up survey. Data from those 601 participants was used to determine which message was most effective.
In this study, the combination message of “cut out or cut back on” meat and other products appeared to work best. It led to more reduction in animal product consumption than encouraging “vegetarian” eating (the difference was statistically significant) or “vegan” eating (the difference was trending toward statistical significance).
Encouraging readers to “eat less meat” appeared to perform second best, but there were no statistically significant differences between it and the other three messages.
The effectiveness of the different messages remained in the same order when translated to days of animal suffering spared.
The data from the current study suggest that the combination message of “cut out or cut back on” meat and other animal products may be more effective than encouraging “vegetarian” or “vegan” eating for getting people to reduce animal product consumption.
We also found that the study’s small control group, which was not given any booklet, reported changing its meat consumption the most, which is unexpected and counter-intuitive. These results may be because control group members viewed booklets given to other members in the study (which is likely, based on how the study was conducted), or because the sample size (57) and power for the control group is so low that the results are statistical noise. We discuss this further in the report.
Pending further studies, we consider the conclusion of this report to be tentative. In the interest of full transparency and in order to inform the design of future studies, we report the results in full despite the tentative nature of the conclusions of this study.
Full Report and Data Set
|Document (with link)||Description|
|Full report||pdf file|
|Full data set||Excel spreadsheet|
|Booklet K, Booklet O||“Cut our or cut back on” message booklets|
|Booklet L, Booklet P||“Eat less meat” message booklets|
|Booklet M, Booklet Q||“Vegatarian” message booklets|
|Booklet N, Booklet R||“Vegan” message booklets|