You are wondering what is the Kunstgriff of Behavioural Econ that enabled it to enter econ mainstream?

*Leave the status quo theory untouched, label it normative or logic of choice and
*label new "behavioural" theory submissively (only a) descriptive theory
#EconTwitter

The arena of normative truth is left to the old boys in the club. All the young boyz&gurlz play with descriptive toyz in the new club and do NOT question the existence of the old club.
[T&K Rational Choice and the Framing of Decisions 1986]
... and co-exist happily ever after.

You may wonder: how a theory can be descriptively correct but not normatively -- is the normative theory wrong?
You may also wonder: how a theory can be normatively correct but not descriptively -- are the facts wrong?
You may also wonder: is the descriptive theory ever wrong?

Of course not coz the new boyz&gurlz can always add new variables and don't need a generator mechanism other than invent a behavioural anomaly or irrational bias.

Thank God Rationicus: Falsifications there are also anomalies here.

Hidden easter egg: The word "Kunstgriff" in the first tweet of this thread was never used by K&T -- why did I use it?

The first correct answer wins half a beer!!! /2