Ian Triplett¹, Cathleen Moore¹; ¹University of Iowa

The oddball effect (OE) is a temporal illusion, according to which, rare stimuli (oddballs) are perceived as having a greater duration than more frequent events (standards) even when their physical durations are identical. Aside from frequency, oddballs are typically defined by their having a physical feature which varies from that of the standards (e.g. size, color, shape). In general, the greater an oddball’s “oddness”, the greater the magnitude of the OE. However, this relationship is not strictly linear nor is oddness the only relevant factor. As demonstrated by Tse et al. (2004), the magnitude of the OE can be modulated by dynamics. Specifically, an expanding oddball among stationary standards induced a greater OE than a stationary oddball among expanding standards. The same degree of oddness (expanding vs. stationary) resulted in OEs with different magnitudes, suggesting that dynamics may play a special role in the OE. To test this, we replicated the serial-streaming paradigm from Tse et al. (2004) with all dynamic stimuli — i.e. disks that continuously changed color. The oddball feature was a dynamic increase in size that either began immediately after stimulus onset (Experiment 1) or after a variable, short delay (Experiment 2). Robust OEs were found in both experiments, confirming that (1) the OE occurs even when comparing two dynamic stimuli — i.e. stimuli which have at least one feature which is constantly changing; and (2) that the oddball does not need to be recognized as such from the outset — i.e. a stimulus can be identified as an oddball after the onset of stimulus presentation via the introduction of an unexpected feature change.