The glass transition temperature (T-g), in-plane diffusivity (D), and effective viscosity (n(eff)) were measured for the same thin film system of poly(isobutyl methacrylate) supported by Silica (PiBMA/SiOx). We found that both the Tg and D were independent of the film thickness (110), but n(eff) decreased with decreasing h(0). We envisage the different 110 dependencies to be caused by Tg, D, and neff being different functions of the local T-g's (To) or viscosities (n(i)), which vary with the film depth. By assuming a three-layer model and that T-g(h(0)) = (Th-g,Th-i)., D(h(0)) similar to k(B)T/(n(i)), and n(eff)(h(0)) h0(3)/3M(tot),(n(i)), where (...) denotes spatial averaging and M101 is the mobility of the films, we were able to account for the experimental data. By extending these ideas to the analogous data of polystyrene supported by silica (PS/SiOx), a resolution was found for the long-standing inconsistency regarding the effects of confinement on the dynamics of polymer films.