We investigated sensitivity for the vertical meaning of the German particle ab by means of stimulus-response compatibility effects. In German, the particle ab is ambiguous and can take on a vertical meaning (downward) as in Auf und Ab (engl. up and down), but it can also take on nonvertical or nonspatial meanings as in Ab und An (engl. from time to time). We show that the particle ab only creates a spatial compatibility effect relative to the German particle auf (Experiment 1) but not relative to the particle an (Experiment 2). Furthermore, as participants executed upward versus downward responses in both Experiments 1 and 2, the mere vertical antagonism of the responses was insufficient to instill a verticality-based compatibility effect. In addition, the compatibility effect was restricted to the transparent version of the particle. If a letter sequence corresponding to the particles was presented in a semantically and morphologically opaque way (e.g., the letters ab were embedded in the German word knabe, engl. boy), no compatibility effect was found, underlining that the effect was due to word meanings rather than visual features. The results underscore the boundary conditions for using compatibility effects in investigating lexical and semantic spatial processing in humans.
Keywords: compatibility effect; semantic processing.