The word 'signalling' is often used in Less Wrong, and often used wrongly. This post is intended to call out our community on its wrongful use, as well as serve as an introduction to the correct concept of signalling as contrast.

"We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard.."

- John F. Kennedy

Why do peacocks grow such large, conspicuous tails? Why do people take degrees in subjects like Philosophy or Classics, despite these subjects having no obvious practical value? Why do people take pains to avoid splitting infinitives, even though everyone can understand split infinitives perfectly well?

These activities seem completely pointless, costly and difficult. Paradoxically, it is probably this very difficulty that serves to explain why they are done at all. Take the peacock’s tail. A peacock that has to struggle to survive while dragging around a conspicuous tail is clearly at a disadvantage. But if he can continue to survive, then clearly he must be pretty strong! So the peahens may choose to mate with him rather than the peacocks with less conspicuous tails, whose survival is thus a less impressive feat.

As for classics, getting a degree in classics may be pointless, but it’s also difficult. It requires one to read and memorize vast chunks of text, and to translate these texts between Greek, Latin and English precisely. So a person who has a degree in classics and got a good mark must be a person with a good memory who is able to execute tasks precisely. Qualities extremely useful in a civil servant, the occupation where many budding classicists find themselves. The rule that you mustn't split infinitives derives from Latin where splitting infinitives was impossible. So a person who doesn’t split infinitives is more likely to be a Latin scholar, with the qualities of class and intelligence that such a thing implies.

Even the decision to go to the moon might be explained in this way. Carl Sagan made the point that a rocket capable of going to the moon is certainly capable of reaching Moscow. And it’s clear why Kennedy in the middle of a Cold War would want to demonstrate such a thing.

When we explain a behaviour in this way, we say that the behaviour is signalling. The agent does not perform a task for its own sake, but to show others that they possess some important quality such as strength, a good memory, or military supremacy. The key features that a behaviour must possess for signalling to be a good explanation are as follows.

1. The behaviour seems pointless. This of course, is a matter of perspective. Peacock’s tails are beautiful, classics is interesting, and the moon landing was a crowning moment of awesome from humanity. Peacock’s tails seem pointless when viewed as struggling to survive and reproduce, classics when viewed as a matter of finance, and the moon landing when viewed as a matter of military strategy. Priorities that genes, most people, and the American government might be expected to have.
2. The behaviour requires a certain quality. Going to the moon requires a good rocket, surviving with a conspicuous tail requires strength and cunning, getting a good grade in classics requires a good memory. This is actually a stricter condition than necessary. All we need is for the quality to lower the cost of the behaviour. In the absence of superior rocket technology, a moon landing could be faked, but only by taking extraordinary and costly steps. This was argued by Messrs Mitchell and Webb here.
3. You want others to believe you have this quality. Peacocks want to look strong and sexy, civil service applicants want to look intelligent and diligent, America wants to look innovative and powerful.
4. Dishonest signalling isn’t worth it. By dishonest signalling, I mean enaging in a signalling behaviour when you don’t possess the quality you wish others to think you have. A weak peacock who grows a conspicuous tale will be eaten by predators. A stupid person who tries to get a degree in classics will fail his subjects. Faking the moon landing carries the risk that the conspiracy will be exposed and the American government would become a laughing stock. A good way of remembering this criterion is the slogan "You can't signal to rubes."

Unfortunately, not all proposed explanations involving the word "signalling" take care to establish these four properties. Our community seems especially guilty of this. The main misunderstanding is that it uses ‘signalling’ merely to denote behaviours that trick rubes in to thinking you’re good. This raises the question of why there are rubes to trick in the first place. Why haven’t more savvy competitors eaten their lunch? Here is an example of someone thinking that you can signal to rubes:

In other words, it's all about signaling, isn't it? Managers will take actions that actively harm the continued progress of the project if that action makes them look "decisive" and "in charge".  I've seen this on many projects I've been on, and it took me a while to realize that my managers weren't stupid or ignorant. It's just that the organization I was working in put a higher priority on process than on results. My managers, therefore quite rationally did things that maximized their apparent value in the eyes of their bosses, even if it meant that the project (and, as a result) the entire organization was hurt.

Here the rube is the managers bosses, why are they so stupid as to think that mismanagement is evidence of superior management qualities? Why haven’t these idiots been sacked? (This probably does occur in real life, but I don’t think "signalling" is the right term to describe it. I would describe it as "pandering to the prejudices of idiots".)

Another comment which falls in to the same trap:

Compare the skilled butcher, who, with no wasted movements, cuts his meat just where the joints are, and the flashy butcher, whose flourishes make for less skilful and efficient cutting but send a more impressive signal.
I agree that the flashy butcher could became engaged in his cutting and lose consciousness of the crowd and his impression on it without decreasing his signalling behaviour. If he did so, he might become more sincere, but his signalling behaviour would remain. For signaling is not a conscious addition to his art, which might strip away: skill at cutting and skill at signalling are woven confusedly together in it.

The trouble here is that it postulates stupid customers, just like the previous comment postulated stupid bosses. A much better test of butcher quality than flashiness is how good the meat tastes and how much is produced. An intelligent customer can probably test this fairly easily, and would not buy meat from the flashy butcher.

These uses of "signalling" at least have the advantage that they’re explanations along economic lines. The difference between signalling and pandering is the intelligence of your audience. What’s worse is that some people in our community use the word "signal" to mean "show" or "pretend".

An example:

I may have learned that signalling low status - to avoid intimidating outsiders - may be less of a good strategy than signalling that I know what I'm talking about.

A low status person that knows what they’re talking about? I suppose such things are possible... Seriously though, "signalling" is being used to mean "tricking people in to thinking that you are". Either you know what you’re talking about or you don’t. At least one of the two options given in the quote will result in you trying to trick someone. We’re signalling to rubes again.

Worst of all, some people use "signalling" as a version of ad hominem. "You just say that to signal." A comment to Overcoming Bias’s controversial post "Gentle, Silent Rape" reads:

“I'm sad but not at all surprised that so many of these comments are to the effect of "HOW DARE YOU EVEN THINK ABOUT THIS TOPIC?!!?!?"
I can only imagine how much more frustrating it must be for Professor Hanson have to deal with increasingly harsh anti-mind climate that envelopes the Western world. The all-encompassing ideology of political correctness is truly a fearsome juggernaut.
I think the status signaling arguments are right on the money, and the rest of the comments serve as the proof.”

Let’s go through the criteria again:

1. The behaviour seems pointless.

This clearly doesn’t apply. The behaviour is easily explicable. Comments might be made out of genuine disagreement, or (more cynically) to intimidate Hanson and others away from making arguments like these in the future.

2.The behaviour requires a certain quality.

The quality proposed was "status", but outrage is cheap. Any fool can be outraged at a blog post mentioning rape. It doesn’t require exceptional intelligence, charisma, wealth, or feminist credentials. You could be homeless and leave an outraged comment just by going to a public library. You don’t even have to read the post.

3. You want others to believe you have this quality.

Well this seemingly applies. People do want to be thought of as being against rape, and high status. The only trouble is that many of the comments are left anonymously.

4. Dishonest signalling isn’t worth it.

This does not apply at all. Even a convicted rapist could leave an outraged comment.

Clear thinking requires making distinctions. Using the word "signalling" to mean "pandering", "tricking people", "showing", or "toeing the party line" does nothing but lead to confusion and muddle. If you’re going to use jargon, use it in its precise sense. That’s what is jargon is for, communicating precisely. Next time you feel like using the word "signalling", ask yourself whether the four criteria apply. Remember: You can’t signal to rubes.