[en] Two models for the dynamics of superfluid ⁴He are studied both quantitatively and theoretically. The Zawadowski-Ruvalds-Solana (ZRS) model of quasi-particle interactions is used to calculate the spectra of neutron scattering and light scattering from liquid helium. It is found that the ZRS model cannot quantitatively describe the observed neutron scattering spectrum, and that the model can account for the experimental light scattering spectrum only if a restrictive assumption is made about the form of the quasi-particle coupling. The ZRS model is shown to be incapable of satisfying an excluded volume condition on the light scattering spectrum. A second model, suggested by the structure of a theory of boson pairing similar to the BCS theory of fermions, is constructed. It is shown that the two-branch long-wavelength excitation spectrum which emerges from the pairing model can describe the low-temperature anomaly in the ⁴He specific heat without contradicting existing direct measurements of the excitation spectrum. Some features of a possible microscopic theory of the two-branch spectrum are discussed