A 2AFC Simultaneity-judgment Task to Estimate the Point of Subjective Simultaneity

Abstract

Currently, the most popular tasks with which to investigate the perception of subjective synchrony are the temporal order judgment (TOJ) and simultaneity judgment (SJ). Here, we consider a modified approach for estimating a point of subjective simultaneity (PSS) by using a two-alternative forced-choice SJ task, in which two audiovisual pairs are presented on each trial and the observer must select the most synchronous pair. To validate the approach, we tested 24 participants on the new 2AFC SJ task alongside both TOJ and simple RT tasks (all completed using the same stimuli). We interpreted responses in these tasks using detection-theoretic models of temporal judgments, which assume variable transmission latencies for sensory signals traversing the brain. While the three tasks provided similar estimates of the PSS on average, correlations across participants on this measure were quite weak. However, model-based (and, thus, comparable) measures of sensory/decision noise revealed a significant correlation across subjects between TOJ and 2AFC SJ tasks, but suggested a greater contribution of decision noise in the TOJ task. Our study establishes the practicality of the 2AFC SJ task, but also illustrates the additional complexity of the procedure. We consider ways in which this new task might complement existing measures when estimating the PSS and assessing psychological models of the temporal judgment process.