Increase in Numerical Magnitude from Left-to-Right Shortens Perceived Time

The present study examined the effect of viewing spatially ordered numbers on time perception. Five single digits were presented as the test stimuli. The digits were chosen from 1 to 9 and presented in a horizontal line. We tested the arrangement of the digits in three conditions, where numerical magnitude of the digits increased from left to right (Small-Large condition), decreased from left to right (Large-Small condition), or in a random order (Random condition). Observers were asked to reproduce the presentation duration of the stimuli by pressing the spacebar for as long as the stimulus had been presented. The results showed that the reproduced time was shorter in the Small-Large condition than the other two conditions. The effect of numerical order on time perception is discussed from the perspective of the mental representation of numbers and fluency of cognitive processing.