My previous post was prompted by an article in the new edition of The Philosophers' Magazine. In this piece by Joshua Knobe, entitled "Is morality relative? Depends on your personality", the author cites empirical research that casts doubt on whether the folk are simply objectivists, as many philosophers tend to assume (hey, even I tend to assume this).
The research relied upon by Knobe suggests that some people are more inclined to objectivism than others. It also finds that we tend to start out as objectivists but to shift away from it towards some more relativist understanding as we mature - though we tend to shift back towards objectivism in middle age. Interestingly, relativism tends to correlate with the psychological trait of openness to experience. You can, predictably enough, also get different intuitions from people depending on what questions you ask them, with radical scenarios involving space aliens proving more effective in eliciting relativist intutions than scenarios involving differences in opinion among people of the same society or different human societies.
The article is only a summary of an interesting line of research that is going on in experimental philosophy, but I'd be interested to see more of the results and to watch how this area develops.
If the research continues to paint a picture of mixed and rather volatile perceptions on the part of the folk, it will not invalidate sophisticated relativisms and sophisticated versions of error theory, to the extent that they agree with each other. In other words, it won't invalidate any reasonably sophisticated anti-realism. But it will seem to indicate that neither error theory of the usual kind nor the kind of sophisticated relativism that has been influenced by Gilbert Harman is quite right. Both kinds of theory would need some revision to their moral semantics, and would need to head in each other's direction.
I think the result would still, arguably, be an error theory, but not as radical in that respect as some of what is said in the name of error theory. I don't think it should necessarily bother J.L. Mackie - if he were still alive - because Mackie was pretty alert to the messiness of moral semantics.