Groechenig, Wyss and Ziegler have recently proved a conjecture of Hausel and Thaddeus concerning an equality between stringy Hodge numbers  of moduli spaces of Higgs bundles for SLn and PGLn. A crucial ingredient in their approach is the use of p-adic integration in the fibres of the Hitchin fibration. We will present a motivic version of their result which is obtained by using motivic integration. This is joint work with Dimitri Wyss.