Walking on a mental time line: Temporal processing affects step movements along the sagittal space

Time is often conceptualized in terms of space (mental time line; MTL). A prevalent representation of temporal concepts, indeed, construes the past and the future as respectively behind and in front of the ego. Insofar, however, a major omission of this line of research is that manual responses were restricted to the frontal space. This work provides the first striking demonstration that temporal processing affects the motor programming of active whole-body movements. Participants initiated steps backward much faster in response to past-than to future-related words, whereas they were faster to step forward in response to future-than past-related words. Furthermore, since the reported compatibility effect was limited to movement initiation time, it is likely that the processing of temporal information acted on the early stages of response selection (see Ulrich et al., 2012). Beyond substantiating the longstanding hypothesis that humans spatialize time on an egocentric spatial frame of reference, our findings demonstrate that the intangible domain of time extends to the more concrete domain of space through our body's action in the physical world.