How are space and time represented in the human mind? Here we evaluate two theoretical proposals, one suggesting a symmetric relationship between space and time (ATOM theory) and the other an asymmetric relationship (metaphor theory). In Experiment 1, Dutch-speaking participants saw 7-letter nouns that named concrete objects of various spatial lengths (tr. pencil, bench, footpath) and estimated how much time they remained on the screen. In Experiment 2, participants saw nouns naming temporal events of various durations (tr. blink, party, season) and estimated the words’ spatial length. The implicit length encoded in object nouns modulated time estimates, but the implicit duration encoded in event nouns did not affect estimates of spatial length. Nouns that named short objects were judged to remain on the screen for a shorter time, and nouns that named longer objects to remain for a longer time. By contrast, variations in the duration of the event nouns’ referents had no effect on judgments of the words’ spatial length on the screen. This asymmetric pattern of cross-dimensional interference cannot be attributed to differences in the discriminability or perceptual salience of space and time in the stimuli. Results support metaphor theory and challenge ATOM.