  Using modern amplitude techniques we compute the leading classical and
quantum corrections to the classical gravitational potential between two
massive scalars induced by adding an $R^3$ term to Einstein gravity. We then
study the scattering of massless scalars, photons and gravitons off a heavy
scalar in the presence of the same $R^3$ deformation, and determine the bending
angle in the three cases from the non-analytic component of the scattering
amplitude. Similarly to the Einstein-Hilbert case, we find that the classical
contribution to the bending angle is universal, but unlike that case,
universality is preserved also by the first quantum correction. Finally we
extend our analysis to include a deformation of the form $\Phi R^2$, where
$\Phi$ is the dilaton, which arises in the low-energy effective action of the
bosonic string in addition to the $R^3$ term, and compute its effect on the
graviton bending.
