I suspect you already knew this but it's a spot on observation, though I think you meant to say increase the mids
Edited 6 minutes ago by Phil Starr
It also shows why, especially at more moderate volumes, bass amps need a lot more power than guitar ones.
There are lots of variations on those curves (phons are psycho acoustic so not everyone perceives the same change in volume, indeed drops and increase in volume are perceived differently). Here a perhaps more typical graph. The average is about 6-9dB/octave in the 50-200Hz range which differentiates between guitar and bass: