Past on the ground floor and future in the attic: The vertical mental timeline

Time is represented along a horizontal mental line with an association between the past (or short duration) and left space as well as between the future (or long duration) and right space. A possible vertical time representation is also supposed to exist, even if results are contradictory depending on the stimuli and response keys used. The aim of the present study was to test the presence of a vertical representation of temporal expressions, overcoming possible methodological limits. In Experiment 1, 167 Italian students had to categorize 20 Italian temporal expressions that appeared at the center of the screen with two analogous vertical response keys ("down" and "up" arrows of a regular keyboard). Specifically, in Experiment 1A participants pressed the down arrow with their left hand and the up arrow with their right hand, whereas in Experiment 1B the key-hand assignment was reversed. In Experiment 2, 25 participants underwent the same procedure using a vertically positioned response box. The same participants also performed a Time-to-Position task, in which they located temporal expressions along a vertical line. In both experiments, a space-time interaction was found, with an association between past expressions and the bottom (or down arrow) response key as well as between future expressions and the top (or up arrow) key. The results suggest a bottom-to-top mapping of time representation, according to the "more-is-up" metaphor.