So, what became known as behavioural economics was 100% started by two psychologists, Daniel Kahneman and Amos Tversky.

While they investigated new topics (i.e. economics), their methodologies were 100% within the standard practice of social and cognitive psychology at the time.

They were then awarded the Nobel Prize for this work. Now, not everyone in the field came from psychology, but a lot did, and the methods used in behavioural economics are essentially indistinguishable from those used in psychology.

For references, Thinking Fast and Slow is probably the best source, as one of the original authors describes their research program.

I understand what you are saying, but on the other hand we don't call calculus "physics" just because it was introduced by Newton (and Leibniz, yeah yeah).

Also, modern economics use some heavy mathematical tools, yet nobody says its a branch of mathematics.

And lastly, psychology is in my opinion one of the most important branches of science right now.

I think that behavioural economics is it's own thing now, but it is heavily inspired by psychology (and, in it's turn, has helped to inspire psychology).

I agree with you on psychology's importance, but that's probably because I am a psychologist :)

Why is psychology important right now? What have psychologists done for me lately?