How are the domains of space and time related? One approach, A Theory of Magnitude (ATOM), proposes an undifferentiated system of magnitude representation in the brain, predicting that space and time are symmetrically related, while Conceptual Metaphor Theory (CMT) proposes that we represent time using spatial metaphors, predicting asymmetrical interactions between domains. Tau and Kappa effects are perceptual phenomena that arise when observers judge the distance/duration between consecutive stimuli in sequence: Timing affects the perception of space (Tau) and spacing affects the perception of time (Kappa). Interference bidirectionality has been taken as evidence for ATOM. CMT proponents argue that interference may result from the perceiver imputing velocity to the stimuli. Here, the Tau and Kappa paradigm was modified to reduce the illusion of imputed velocity by manipulating stimuli parameters. In favor of CMT, we found that when the illusion of imputed velocity is reduced, asymmetrical interference arises: the Tau effect is eliminated while the Kappa effect remains intact.