What is a research credit?

Interrogating a sectoid resulted in my earning a research credit, the exact message being:

Research Credit Earned: Beam Weapons

However, the game doesn't explain what a research credit is.

What is a research credit?

Solution 1:

It means that the research time for all future research projects which fall into this category is now reduced.

When a research project is affected by a research credit you obtained, its project description will end with the phrase "XYZ research credit applies".

Most alien interrogations will give you some kind of research credit. That means it's usually a good idea to prioritize alien interrogations over other research projects.

Most research credits decrease research time in a specific category by 50%, although there is one that reduces all research time by 25%.

When you want to know which alien species gives you which research credits, and you don't mind MASSIVE SPOILERS, you could look at the answer to this question: What does the full research tree look like?