Time perception is a fundamental aspect of many perceptual and cognitive functions. It enables us to perceive the world in a temporally consistent manner. Nonetheless, time perception is highly susceptible to non-temporal information. Indeed, many temporal distortions of sensory events have been reported in the past few decades, and researchers have used such illusions as a tool to investigate the psychological and neural processes that are related to the representation of time. One of the prominent illusions is the temporal oddball effect, in which a novel stimulus is perceived to last longer in duration than a repeated stimulus. Numerous studies tried to reveal the underlying mechanisms of this illusion, and several theoretical frameworks have been developed to account for the experimental findings. However, the perceptual and cognitive bases of the temporal oddball effect remain unclear, and further integrated discussion is required. Here, we review three influential hypotheses (i.e., pacemaker hypothesis, repetition suppression hypothesis, and perceptual strength hypothesis) of the temporal oddball effect and summarise critical findings that provided empirical evidence for each hypothesis. We then discuss the sensory process that plays a key role in the oddball effect and the avenues for future research on time perception.
