  We developed a Bayesian framework to determine in a robust way the relation
between velocity dispersions and chemical abundances in a sample of stars. Our
modelling takes into account the uncertainties in the chemical and kinematic
properties. We make use of RAVE DR5 radial velocities and abundances together
with Gaia DR1 proper motions and parallaxes (when possible, otherwise UCAC4
data is used). We found that, in general, the velocity dispersions increase
with decreasing [Fe/H] and increasing [Mg/Fe]. A possible decrease in velocity
dispersion for stars with high [Mg/Fe] is a property of a negligible fraction
of stars and hardly a robust result. At low [Fe/H] and high [Mg/Fe] the sample
is incomplete, affected by biases, and likely not representative of the
underlying stellar population.
