Abstract concepts are traditionally thought to differ from concrete concepts by their lack of perceptual information, which causes them to be processed more slowly and inaccurately than perceptually-based concrete concepts. We examined this assumption by comparing concreteness and imageability norms to a set of perceptual strength norms in five separate modalities: sound, taste, touch, smell and vision. Results showed that that concreteness and imageability do not actually reflect the perceptual basis of concepts: concreteness ratings appear to be based on two different intersecting decision criteria, and imageability ratings are visually biased. Analysis of lexical decision and word naming performance showed that maximum perceptual strength (i.e., strength in the dominant perceptual modality) consistently outperformed both concreteness and imageability in accounting for variance in response latency and accuracy. We conclude that so-called concreteness effects in word processing emerge from the perceptual strength of a concept’s representation and discuss the implications for theories of conceptual representation.