How did Scotland grow so quickly?

Scotland had been an economic backwater at the time of the 1707 union with England. By 1770 at least the Scottish cities were among the most developed and intellectually advanced parts of Europe. How could this happen?

Arthur Herman supplies at least one piece of the puzzle:

...the fact that Scotland was very much the junior partner in this union also turned out to be an advantage. The new Parliament largely ignored Scotland; outbursts such as the malt riots and the threat of Jacobitism apart, the government in London paid little attention to what was happening north of the border. Scots ended up with the best of both worlds: peace and order from a strong administrative state, but freedom to develop and innovate without undue interference from those who controlled it. Over the next century, Scots would learn to rely on their own resources and ingenuity far more than their southern neighbors would...

A strong government that leaves well enough alone: this was the dual, seemingly contradictory, nature of the British state as it became part of life in post-union Scotland. Scots became used to these dualities, and learned to accept them as basic reality, just as the Union itself involved a fundamental duality: "a ship of state with a double-bottomed hull," as Jonathan Swift put it. They also learned to think in a new way as a result of the Union: in terms of the long term.

Many economic development problems today stem from a similar conundrum. Ideally we would like a state that is both strong and not too large. Most parts of the world are unable to institute this duality; of course Hong Kong was a notable exception. I am not in general an imperialist, but the most successful instances of imperialism are likely to be highly successful indeed.