Let's say you are recruiting two groups of people, English monolinguals and bilinguals. If you're having a hard time recruiting enough bilinguals, the natural, free-market thing to do would be to offer to increase how much they are compensated to attract more.

Assuming that both groups complete similar activities in the same time frame, is it unethical to pay one group more than another?

Would the answer be the same if the quality wasn't the part of the design? For example, if your monolingual group is older on average, is it unethical to post an advertisement for an increased rate for young monolinguals to bring your group averages back to comparable?

I have never seen a research group do this, presumably because of how time-consuming it would be to do, but I haven't found anything to suggest that it is wrong to do.

I'm asking here because I briefly discussed this idea with someone, and she seemed to think the IRB would take an issue with it but we didn't got much further.

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    It's difficult (=impossible) enough to prove that a mono- and bilingual test group are comparable. Not unethical, but impractical. – Karl Jul 23 '18 at 20:45
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    Also: How could this be unethical, unless you made it a secret? Ethical is NOT the same thing als "someone might be unhappy about it". Actually it is directly orthogonal to that: It's a very important feature of acting ethical that you do it regardless of someone not liking it. – Karl Jul 23 '18 at 20:51
  • @Karl Well, it was mostly an illustration but there are plenty of people who regularly do research like that. As to your second point, I'm not sure what secrecy has to do with it, or where I suggested not doing it because "someone might be unhappy about it." Perhaps you should expand your thoughts into an answer. – Azor Ahai -him- Jul 23 '18 at 20:54
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    I wonder how you got to the idea that this might be unethical. Perhaps you want to elaborate. – Karl Jul 23 '18 at 21:14
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    @emory That is also a fair question, but I decided to leave gender out of it because this website is terrible about discussing gender and I felt that including it would lead to a huge comment chain about that instead of the heart of the question. – Azor Ahai -him- Jul 24 '18 at 15:47

I don’t see on what grounds anyone could regard this as unethical, but one might legitimately wonder whether paying the two groups of participants unequally might inadvertently create a bias that would compromise the integrity of your conclusions. After all, your research is presumably premised on the assumption that the participants from the two groups are both fairly typical representatives of those groups. But if you pay participants from one group $10 and those from the other (for argument’s sake) $5000, the participants you’re likely to get in both groups might differ in some ways that you didn’t expect - for example, the lower-paid participants might be people who are more motivated by an altruistic desire to help scientific research than the higher-paid participants

Whether this is a genuine concern or not depends on the difference in the pay and on the precise nature of your study, but it’s something to think about.

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    +1. Good to raise the point about large differences. Also to remind about unintended consequences – Buffy Jul 23 '18 at 19:29
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    If the "quality" is membership in a protected class (gender, race, age, sexual orientation, etc) then it is probably unethical and illegal. – emory Jul 24 '18 at 15:53
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    On the other hand, it might create a bias if you pay not enough to get representative members of a poorer class. – Azor Ahai -him- Jul 30 '18 at 2:58

I don’t think that this is unethical. You’re trying to hire people to do a task for you, and paying rarer skills/more difficult tasks more makes sense. You might have to justify why you’re doing it to an IRB, but I don’t see this as unethical of as compromising the study.

In fact, there are experiments that run all the time where participants are paid unequally: prisoner’s dilemma-type ones, where performance influences payment.

EDIT: To clarify, I agree that in many cases it is poor design to do this. The questioner is specifically interested in two things however: is it ethical and would an IRB care. Yes, the example of prisoner's dilemmas for $5 or given children gumdrops for playing a game well or something like that is pragmatically very different. However, it is not ethically different in my mind, and the fact that those studies are wide-spread and uncontroversial AFAIK is strong evidence that the practice isn't inherently immoral.

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    The Prisoner's Dilemma example does not apply here. In the latter, the unequal payment is part of the design, but in OP's question it is a meta-feature which therefore "loads the dice" of the experiment outside of its scope. – Captain Emacs Jul 24 '18 at 4:53
  • @CaptainEmacs Why do you say it does not apply? It seems like a clear analogy to me. Just because they are different in one aspect doesn't mean that the same principle may not apply. – 6005 Jul 24 '18 at 5:19
  • Prisoners dilemma is not about unequal pay. It isn’t about pay at all. It’s about strategies in which singly beneficial strategies seem the better option but actually mutually beneficial strategies are far better for everyone but also less attractive to the individual. – Fogmeister Jul 24 '18 at 5:42
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    @CaptainEmacs I think what Stella is saying is that as far as the ethics question is concerned, the fact that in some well-known experiments participants are paid differently (even as part of the experiment’s design, as you point out) illustrates that there is no ethical problem. That sounds correct to me. Your point that the two are not comparable has to do with the effect of the differential payment practice on the validity of the research, rather than the ethics. It is a valid point as well (and closely related to what I discussed in my answer), but you are talking about different things. – Dan Romik Jul 24 '18 at 5:53
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    @Fogmeister First of all, I made the wrong comment here, as Stella answered the ethical question while I commented on experimental design. As for your comment, I do not understand it. Whatever the currency is by which you run PD-type experiments, and whatever you want to prove with them - the point is that it's ok to have an experiment have differing payoffs to study incentives. But if the pay happens outside of the experiment (as per OP's question), it biases the sample. Which is what Dan Romik points out and my comment reiterates (even if not precisely addressing Stella's response). – Captain Emacs Jul 24 '18 at 10:07

Clearly you are not obligated to pay everyone the same. You are not even obligated to have an objective reason for the differing pay: There are plenty of papers in economics and psychology where some subjects are given more money than others because that is the experiment (for example, basic income studies).

However, if your compensation scheme is perceived as unfair, this may be a barrier to getting approval or being published.

Also, you are ultimately employing people for a task, and many countries have legislation regulating employment. You want to make sure you do not run afoul of these laws and get punished by the state. Your example sounds like one could argue that it discriminates on national origin, which in the US for instance can be a crime. But to be sure, discriminating on the basis of being a native speaker for scientific studies is definitely allowed in the US.

But generally, I don't think it is unethical. If, for instance, native speakers are much harder to find in your area, it makes sense to pay them more just to make sure you have enough of them. If you are comparing native and non-native speakers in your study, and presumably your funds are not infinite, attempting to pay everyone the same may result in having so few native speakers in your sample so as to invalidate your results, or not being able to afford the study with your funding. Likewise, if there are certain statistical tendencies in your groups that would introduce confounds, of course there is nothing wrong with attempting to eliminate these.

If anything, the line separating the unethical (and illegal) would rest with your motive: If you have a sound scientific reason for adopting this compensation scheme ("we can't afford to pay everyone more" counts), it's probably ok.


This is a general social/economic/polticial question.

I would say this question is way out of scope. I mean, fair enough, you come up against it in an academic setting, but really:

  • Is it ethical to pay people more, or less, because of pre-existing conditions which are not under their control?
  • Is it ethichal to pay people more, or less, because of conditions which are due to a mistake they have made, which in hindsight they would not have?
  • Is it ethical to pay people according to their performance on the job, rather than according to their needs? One person does twice the work than his/her colleague, but is single and healty; the other supports a spouse and children, and has some ongoing medical condition.
  • Is it ethical to pay young people less because they are less experienced and knowledgeable, and are in junior positions, even though young adults typically have less or no savings to rely on and their expenses are typically much higher than those of people at age 40 or 50?

These are all deep, serious issues to contend with - regardless of whether you're in academia. I could write a book about it (if I had the time and perseverance); and I'm sure prominent social thinkers and philosophers have.

  • This sounds like you're answering a question about wages/salary, not about volunteer compensation, which I'm not sure how much things transfer. – Azor Ahai -him- Jul 24 '18 at 15:46
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    @AzorAhai: "Volunteer compensation" is a contradiction in terms. This is a question about payment for doing work - which may be just investing time in performing an experiment. OP said s/he is recruiting and is wondering about inequality of pay. – einpoklum Jul 24 '18 at 16:58
  • You’re making a mountain out of a molehill here. The answer to OP’s specific question is “no” (it’s not unethical). It’s not a deep question at all, and no book-length treatise is required to answer it. (The other questions you raised also seem fairly easy to answer, but in any case they don’t seem to have much connection to what OP is asking about.) – Dan Romik Jul 24 '18 at 19:00
  • @DanRomik: IMHO, you think OP's question is a molehill because you think the wider questions are fairly easy to answer. They aren't. – einpoklum Jul 24 '18 at 19:52

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