Motivic invariants of quivers via dimensional reduction

We provide a reduction formula for the motivic Donaldson-Thomas invariants associated to a quiver with superpotential. The method is valid provided the superpotential has a linear factor, it allows us to compute virtual motives in terms of ordinary motivic classes of simpler quiver varieties. We outline an application, giving explicit formulas for the motivic Donaldson-Thomas invariants of the orbifolds $[\CC \times \CC^2/\ZZ_n]$.