A new cognitive architecture for the syntactic aspects of human sentence processing (called Unification Space) is tested against experimental data from human subjects. The data, originally collected by Bach, Brown and Marslen-Wilson (1986), concern the comprehensibility of verb dependency constructions in Dutch and German: right-branching, center-embedded, and cross-serial dependencies of one to four levels deep. A satisfactory fit is obtained between comprehensibility data and parsability scores in the model.