An electron temperature anisotropy T⊥e > T∥e (where ⊥ and ∥ refer to directions relative to the background magnetic field) can excite the whistler anisotropy instability in a collisionless plasma. The resulting enhanced fluctuating magnetic fields scatter the electrons and reduce the anisotropy. We use particle-in-cell simulations in a spatially homogeneous plasma model to compute the maximum values of the wave-particle scattering rate for electron anisotropy reduction. This rate scales as the electron cyclotron frequency but, for a fixed initial growth rate, is relatively independent of the electron temperature if kBTe ≤ 5 keV. For larger electron temperatures, the scattering rate decreases with increasing Te, suggesting that relativistic effects play a role.