Computer-based learning environments offer the possibility to present interactive simulations, which students can manipulate and explore and allow studying functional relations actively. Animations like a short video clip offer - besides interactive simulations - an alternative method for visualizing the dynamic behavior of a complex subject matter. With an animation the problem that students are cognitively overtaxed by the degree of freedom the simulation allows or that they are unable to find suitable hypotheses for experimenting does not exist. One can, therefore, assume that the degree of instructional goal orientation (in the sense of assistance to focus on the learning content) is a conditional variable which determines whether learning is better with animations or with simulations. In an empirical study with four experimental groups knowledge acquisition from animations was compared to knowledge acquisition from simulations. In each group there was additional differentiation between a high and a low level of instructional goal orientation. The learning content was a computer-based learning unit in school physics about torques. There were four versions of the teaching unit. The simulations were realized using dynamic geometry modules, the animations with appropriate video sequences. lt was differentiated between a high and low level of instructional goal orientation by using a different length of information text for every animation or simulation. A total of 52 students from three German schools worked on the computer-based learning unit about torques. In the study, learning with simulations resulted in a significantly higher learning effect, both with a high and with a low instructional goal orientation. These results let us assume that explorative learning with simulations is connected with additional requirements for learning, which (in this study) could not be reduced by a higher level of instructional goal orientation. Interactive simulations offer an instrumental support for the development of mental models, but this does not necessarily lead to a better learning effect. Increased instrumental and cognitive requirements through the learning medium can disturb students' learning.