Abstract
It is pointed out that the absolute B(M1) strengths for transitions between low lying states of collective nuclei provide a useful constraint on the possible parametrization of Hamiltonians within the framework of the interacting boson approximation. Some specific examples of recent calculations are cited where, despite good agreement with experimental energies and B(E2) values, some inconsistencies arise when the predictions for low lying M1 strengths are compared with the empirical values.