  We investigate memory effects in the spin-boson model using a recently
proposed measure for non-Markovian behavior based on the information exchange
between an open system and its environment. Employing the numerical exact
multilayer multiconfguration time-dependent Hartree approach, we simulate the
dynamics of the spin-boson model at zero temperature for a broad range of
parameters. For a fast bath, i.e. in the scaling limit, we find non-Markovian
dynamics for a coherently decaying spin at weak system-bath coupling, whereas
memory effects are absent for stronger coupling in the regimes of incoherent
decay and localization. If the time scales of system and bath are comparable, a
complex, non-monotonic dependence of non-Markovianity on the system-bath
coupling strength is observed.
