Described is an aqueous dispersion comprising at least one polymer dispersed in water and having a weight-average molecular weight of less than 50 000 and a glass transition temperature of −40° C. to 0° C., preparable by emulsion polymerization in the presence of at least one chain transfer agent of a monomer mixture comprising at least 40% by weight of C1 to C20 alkyl (meth)acrylates, 0% to 30% by weight of vinylaromatics, at least 0.1% by weight of acid monomers, and 0% to 50% by weight of further monomers. The dispersion can be used in particular as a tackifier for adhesives.