Abstract In psycholinguistics, concepts are considered abstract if they do not apply to physical objects that we can touch, see, feel, hear, smell or taste. Psychologists usually distinguish concrete from abstract concepts by means of so-called concreteness ratings. In concreteness rating studies, laypeople are asked to rate the concreteness of words based on the above criterion. The wide use of concreteness ratings motivates an assessment of them. I point out two problems: First, most current concreteness ratings test the intuited concreteness of word forms as opposed to concepts. This ignores the ubiquitous phenomenon of lexical ambiguity. Second, the criterion of abstract concepts that the instruction texts of rating studies rely on does not capture the notion that psychologists working on abstract concepts are normally interested in, i.e., concepts that could reasonably be sensorimotor representations. For many concepts that pick out physical objects, this is not reasonable. In this paper, I propose a characterization of concrete and abstract concepts that avoids these two problems and that may be useful for future studies in psychology.