Spatial-musical association of response codes without sound.

Humans tasked with pressing a key on a computer keyboard in response to a pitch can respond more quickly to a high-pitched sound by pressing a key higher on the keyboard and to a low-pitched sound by pressing a lower key, compared with the opposite configuration. This so-called spatial-musical association of response codes (SMARC) has been considered to reflect the spatial coding of sound pitch rather than to be an artefact of the verbal labels denoting spatial positions for localising sounds. In this study, we completely excluded the latter possibility, that is, the directional effects of automatic sound localisation on the SMARC effect. We did this by examining whether the SMARC effect occurs without sound; that is, we investigated whether the effect would be elicited by written pitch names alone. We found that when musically trained participants judged pitch height labelled by visually presented word stimuli, the SMARC effect still occurred. This also happened among musically naïve participants when the height of the pitch was explicitly comparable with that of a referential pitch. We also found that musically trained participants exhibited the SMARC effect in response to pitch names even when the indicated pitch height was irrelevant to the task they were asked to perform. These results suggest that the SMARC effect can occur at the semantic level in the absence of sound, clearly excluding the directional effects of automatic sound localisation.