Idea is about signing between two country new kind of tread - civil migration.
It add bonus to developing technologies discovered by at least one country we signed this tread with, but also makes our people unhappy per each technology discovered by at least one country we signed this tread with.
Reason:
In my opinion, that's quite normal people will migrate to more advanced country and information people are living better in those more advanced country makes our people sad. There exist other effect: our people or spies could gather information about advance technologies in this more advanced country.