The space-time interaction suggests a left-to-right directionality in the mind's representation of elapsing time. However, studies showing a possible vertical time representation are scarce and contradictory. In Experiment 1, 32 participants had to judge the duration (200, 300, 500, or 600 ms) of the target stimulus that appeared at the top, centre, or bottom of the screen, compared with a reference stimulus (400 ms) that always appeared in the centre of the screen. In Experiment 2, 32 participants were administered the same procedure, but the reference stimulus appeared at the top, centre, or bottom of the screen and the target stimulus was fixed in the centre location. In both experiments, a space-time interaction was found with an association between short durations and bottom response key as well as between long durations and top key. The evidence of a vertical mental timeline was further confirmed by the distance effect with a lower level of performance for durations close to that of the reference stimulus. The results suggest a bottom-to-top mapping of time representation, more in line with the metaphor "more is up."
