# Technological shocks and Labour supply in RBC and NK models

In the class notes of Eric Sims on RBC and New Keynesian models, in his site, we get to see several graphs with the impulse response functions (IRF) of real variables such as output, labour hours, consumption, etc.

One thing, I don't get is why for the basic RBC (and some extensions) whenever we get a positive tech shock, the labour hours($N_t$) increases, but for the New Keynesian models $N_t$ decreases... Why is that?

Any help would be appreciated.