Through an experiment in a virtual environment, in this work we studied the relationship between vertical and horizontal shelf location and the frequency with which shoppers select items. We tested a random distribution hypothesis of the picking up frequencies (PUFs) in relationship to item shelf position within an experimental framework with various constant hypothesized confounding variables. The equidistribution hypothesis was rejected in a test with 600 virtual shoppers, providing evidence for the existence of a gravitational force towards certain shelf locations. In particular, the PUFs resulted significantly higher for eye-level and waist-level locations when items were placed in the first half of the virtual gondola. On a theoretical level, our experiment also shows that the minimal physical effort principle is probably not a good explanation for the qualitative heterogeneity of shelf space and for the associated shelf position effects. Limitations and managerial implications of our work were also discussed.