Within a one-exciton picture, molecular dimers (M-1-M-2) possess excited states of even and odd parity which correspond to linear combinations of locally excited configurations (M-1*-M-2; M-1-M-2*). If this symmetry is broken, the excitation energy localizes in one or the other monomer. We perform time-dependent quantum calculations on dimer and trimer aggregates which are subject to time-dependent perturbations. The latter induce exciton localizations which are influenced by the monomer vibrational degrees-of-freedom. This influence is characterized by comparison with purely electronic models. (C) 2012 Elsevier B. V. All rights reserved.