This post summarizes a new meta-analysis from the Humane and Sustainable Food Lab. We analyze the most rigorous randomized controlled trials (RCTs) that aim to reduce consumption of meat and animal products (MAP). We conclude that no theoretical approach, delivery mechanism, or persuasive message should be considered a well-validated means of reducing MAP consumption. By contrast, reducing consumption of red and processed meat (RPM) appears to be an easier target. However, if RPM reductions lead to more consumption of chicken and fish, this is likely bad for animal welfare and doesn’t ameliorate zoonotic outbreak or land and water pollution. We also find that many promising approaches await rigorous evaluation.
This post updates a post from a year ago. We first summarize the current paper, and then describe how the project and its findings have evolved.
What is a rigorous RCT?
We operationalize “rigorous RCT” as any study that:
* Randomly assigns participants to a treatment and control group
* Measures consumption directly -- rather than (or in addition to) attitudes, intentions, or hypothetical choices -- at least a single day after treatment begins
* Has at least 25 subjects in both treatment and control, or, in the case of cluster-assigned studies (e.g. university classes that all attend a lecture together or not), at least 10 clusters in total.
Additionally, studies needed to intend to reduce MAP consumption, rather than (e.g.) encouraging people to switch from beef to chicken, and be publicly available by December 2023.
We found 35 papers, comprising 41 studies and 112 interventions, that met these criteria. 18 of 35 papers have been published since 2020.
The main theoretical approaches:
Broadly speaking, studies used Persuasion, Choice Architecture, Psychology, and a combination of Persuasion and Psychology to try to change eating behavior.
Persuasion studies typically provide arguments about animal welfare, health, and environmental welfare reason
Are these constraints on doing harm actually standard among non-consequentialists? I suspect they would go primarily for constraints on ex ante/foreseeable effects per person (already or in response to the paralysis argument), so that
The thresholds could also be soft and depend on benefits or act as a penalty to a consequentialist calculus, if you want to allow for much more significant benefits to outweigh lesser harms.
It might get tricky with possible future people, or maybe the constraints only really apply in a person-affecting way. Building off 3 above, you could sum expected harms (already including probabilities of existence which can vary between acts, or taking the difference of conditional expectations and weighting) across all actual and possible people, and use a threshold constraint that depends on the expected number of actual people. Where u represents the individual utilities in the world in which you choose a given action and v represents the utilities for "doing nothing",
This could handle things like contributing too much to climate change (many possible people are ex ante worse off according to transworld identity) and preventing bad lives. With counterparts, extending transworld identity, you might be able to handle the nonidentity problem, too.
Some constraints might also be only on intentional or reckless/negligent acts, although we would be owed a precise definition for reckless/negligent.
One's modus ponens is someone else's modus tollens.
Michael Huemer wrote something very similar In Praise of Passivity ten years ago, but he bit the deontologist bullet: so (unless you are acting inside the space defined by explicit rights and duties) if you are uncertain of the outcomes of your action, you are doing wrong.