We show a procedure for determining the class of diffusion in systems governed by a generalized Langevin equation with memory. The analysis holds for one-dimensional systems. We provide a simple answer for the diffusive exponent and its relation with noise and memory. We discuss as well limits for mixing, ergodicity and of the fluctuation--dissipation theorem.

PACS numbers: 05.10.Gg, 05.40.Ca, 05.40.Jc