A few weeks ago I published results of a small (n = 50) survey showing that people’s moral valuation of different kinds of animals scaled pretty nicely with the animals’ number of cortical neurons (see here for more on why we might expect that to be true).

A commenter, Tibbar, did a larger survey on Mechanical Turk and got very different results, so I retracted the claim. I wasn’t sure why we got such different results, but I chalked it down to chance, or perhaps to my having surveyed an animal-rights-conscious crowd who thinks a lot about this kinds of things vs. Tibbar surveying random MTurkers.

Now David Moss, from effective altruist organization Rethink Priorities, has looked into this more deeply and resolved some of the discrepancies.

The problem is that I did a terrible job explaining my procedure (I linked to the form I used, but the link was broken when Tibbar did his survey). In particular, I included the line:

If you believe [animals have moral value] in general, but think some specific animal I ask about doesn’t work this way, feel free to leave the question blank or put in “99999”, which I will interpret as “basically infinity”

About 5 – 10% of respondents took me up on this. Tibbar didn’t make this suggestion, and none of his participants did this.

Moss surveyed 490 people on Mechanical Turk, and did not offer people a “basically infinity” option. However, many (20% – 40%) of his participants said the question didn’t apply to specific animals.

He found that when he ignored these, he got the same (low) numbers as Tibbar; when he counted an N/A answer as a vote for “basically infinity”, he got the same (high) numbers that I did.

This graph measures people’s perceptions of how many of each animal is morally equivalent to one human. “Priorities (inclusive)” is Rethink Priorities’ survey, with refusal to vote counted as “basically infinity”. “Priorities (exclusive)” is Rethink Priorities’ survey, with refusals to vote thrown out. I think this demonstrates pretty well that you can get either mine or Tibbar’s numbers depending on which choice you make.

But Moss also points out that all of this is just a fragile balance between people who say every life is worth the same regardless of species, versus people who just spam the box with as many nines as they can.

So it’s not clear how much we should be drawing from this in any case. Whatever. I still think it’s neat.

The moral of the story is to always explain your procedures really well before you try to replicate something. Also to make sure the link to your procedures actually goes to your procedures, although maybe no one other than me has ever made that specific mistake before.