## ABSTRACT

In two experiments we investigated the ambiguous role of surface similarities for the occurrence of sequence effects in problem solving (Scheiter & Gerjets, 2002). We compared two problem sequences consisting of nine algebra word problems, which came from three categories. The surface and structural features of the problems were cross-varied: For each category one corresponding problem with a cover story typical for problems of that category was used. Additionally, two non-corresponding problems were couched into cover stories typical for the other two categories. I.e., each of the three problem categories was combined with each cover story. In the structure-blocked sequence problems were presented in three blocks of structurally identical, but superficially dissimilar problems. In the surface-blocked sequence the problems were presented in three blocks of superficially similar, but structurally dissimilar problems. In both sequences each block began with a corresponding problem, followed by two non-corresponding ones.