Abstract
Crowded letters subjectively last shorter than non-crowded ones (Lavrenteva & Murakami, VSS2020), but the characteristics and possible mechanisms of this phenomenon are yet to be clarified. To examine whether it is specific to letters, we replicated the phenomenon using non-letter vernier acuity stimuli (two horizontally offset vertical lines) as targets. They were presented on a gray background in the periphery of the right visual hemifield and surrounded by horizontally arranged flankers (digital number ‘8’), five to the left and five to the right of the target. In “crowded” stimuli, the nearest flankers shared its color with the target (e.g., white), while all the other flankers had a different color (e.g., black). In “non-crowded” stimuli, only the outermost flankers had the same color as the target. Similar to the letter targets, the non-letter targets subjectively lasted shorter in the “crowded” stimuli than in the “non-crowded” ones. This implies that duration compression depends not on letter identification, but rather on the occurrence of crowding seen in general shape recognition. In another experiment focused on onset/offset timing error as a potential cause, we used similar stimuli but with digital letters as targets. A clock with a constantly rotating hand was presented in the middle to measure the perceived onset and offset of the crowded and non-crowded stimuli. The offset (but not the onset) of the crowded stimuli appeared to lag behind the offset of the non-crowded stimuli. If anything, this contradicts the duration compression of the crowded stimuli. These results are more consistent with a change of pacemaker rate in the pacemaker-accumulator model of time perception, such that the non-crowded stimuli speed the pacemaker up and/or the crowded stimuli slow it down. This study indicates that processing in “what” pathway of the visual system can distort time perception by affecting the internal pacemaker.