motion are the same, in the sense that the displacement under an applied force and the mean-square displacement for diffusion have the same linear or sublinear time dependences, depending on the probe size.

There are sometimes suggestions that probe behavior should approach Stokes’ Law and the Stokes Einstein-equation as the size of the probes is increased. Amblard, et al.’s experiments show precisely the opposite behavior. Deviations from simple diffusion are larger for the larger particles. Whenever particle motion is subdiffusive, the light scattering spectrum will not be a simple exponential. The scattering spectrum will follow eq \[eq:g1sanddisplacements\], showing that the relationship between $g^{(1s)}(q,t)$ and $\langle (\Delta x(t) )^{2} \rangle$ is a neither-way street. Just as one cannot in general calculate $\langle (\Delta x(t) )^{2} \rangle$ from $g^{(1s)}(q,t)$, so also one cannot in general calculate $g^{(1s)}(q,t)$ from $\langle (\Delta x(t) )^{2} \rangle$, because all higher moments of $P(\Delta x)$ are needed in order to calculate $g^{(1s)}(q,t)$.

Discussion\[sectiondiscussion\]
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The primary objective of this paper was to correct a widespread literature error, namely the false belief that that $g^{(1s)}(q,t)$ can in general be used to determine the mean-square displacement of probes in complex fluids. The belief appears to have arisen from a 