Decision processes related to interval timing are commonly examined using the duration bisection procedure-a well-established timekeeping task in which participants make judgments about whether a series of "probes" are closer in duration to a "short" anchor duration or a "long" anchor duration. The specific information used during bisection categorization has been a subject of debate. Recent research involving the Contingent Negative Variation (CNV) suggests that the "short" anchor duration and a value near the geometric mean (GM) of the short and long anchors are among the critical pieces of information used during bisection categorization judgements. The present study examined a corollary of this claim, that memory comparison and decision-making processes related to the temporal judgments are completed prior to probe offset when probe durations are perceived to be "long;" testing the hypotheses that (1) response times would be significantly longer for "short" relative to "long" categorizations and that (2) there would be significant differences in ERPs time-locked to probe offset between probes judged to be "short" and "long." Both of these predictions were realized in the results, providing strong support for the assertion that a value near the GM-likely the point of subjective equality (PSE)-is among the critical information used during bisection categorization judgments.
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