Six in one...

... a half dozen in the other. Tyler Cowen says that education isn't really signalling, so much as it is establishing a sense of self and then projecting that sense of self to others. I guess his point is that as you spend more years being formally educated, you don't just convince others that you can conform, or are smart, or conscientious -- you convince yourself, too.

He also says that this belief in your education, and this sense of self are what make you more productive. I think the self-convincing is little more than self-deception, though to succeed in school for a long time, it helps to be smart, conscientious, and conformist. If I had to guess what actually makes most people more productive, I'd have something like this: productivity = f(ability, conscientiousness, on-the-job-learning). Maybe education develops conscientiousness, or instills in some people the confidence to better tap into innate abilities, but the main point of a signalling theory remains intact: (for the most part) you aren't actually learning concrete things that help you do a job as an adult.