Hard as in a natural science? Yes. Hard is in 1*10^-9 precision in experimental results? No.
The closer you get to largely descriptive biology, like behavioral bio, the further you stray from classical definitions of hard science. The best results are in physiology and molecular biophysics but that isn’t to say the rest of the field won’t be dragged kicking and screaming into the 21st century. A good rule of thumb, the more math and mechanistic theory which has been replicated many times over, the “harder” the science.
