Abstract
The most popular tasks with which to investigate the perception of subjective synchrony are the temporal order judgment (TOJ) and the simultaneity judgment (SJ). Here, we discuss a complementary approach—a dual-presentation (2x) SJ task—and focus on appropriate analysis methods for a theoretically desirable “roving” design. Two stimulus pairs are presented on each trial and the observer must select the most synchronous. To demonstrate this approach, in Experiment 1 we tested the 2xSJ task alongside TOJ, SJ, and simple reaction-time (RT) tasks using audiovisual stimuli. We interpret responses from each task using detection-theoretic models, which assume variable arrival times for sensory signals at critical brain structures for timing perception. All tasks provide similar estimates of the point of subjective simultaneity (PSS) on average, and PSS estimates from some tasks were correlated on an individual basis. The 2xSJ task produced lower and more stable estimates of model-based (and thus comparable) sensory/decision noise than the TOJ. In Experiment 2 we obtained similar results using RT, TOJ, ternary, and 2xSJ tasks for all combinations of auditory, visual, and tactile stimuli. In Experiment 3 we investigated attentional prior entry, using both TOJs and 2xSJs. We found that estimates of prior-entry magnitude correlated across these tasks. Overall, our study establishes the practicality of the roving dual-presentation SJ task, but also illustrates the additional complexity of the procedure. We consider ways in which this task might complement more traditional procedures, particularly when it is important to estimate both PSS and sensory/decisional noise.
Highlights
For observer SM, the 2xSJ task simulation suggested that our simple observer model could plausibly be the generating model for the data when the task was performed alongside the simultaneity judgment (SJ), but not when performed alone, as the deviance of the best-fitting model differed significantly from its expected value in the latter case (p = 0.048)
For observer KY, for the 2xSJ task deviance of the best-fitting model was significantly greater than predicted if our simple observer model were a complete generating model, both when the task was performed alone and alongside the SJ
Given that the 2xSJ task included more trials than the temporal order judgment (TOJ) task in Experiment 1b, and would be expected to provide tighter confidence intervals, for this comparison we looked at fits based only on the first 100 trials of the 2xSJ
Summary
This is part of what we mean when we say that we have a sensation of the passage of time. Determining the relative timing at which two or more events occur would appear to be an important perceptual operation, and one that might underscore various higher-level inferences, such as the causal relationship between events, or the degree to which two events should be grouped perceptually. A Roving 2xSJ Task to Estimate the PSS processes by which the brain determines relative timing require clarification. The problem appears acute for multisensory events, where relevant neural signals might be dispersed widely in space and time. Even within a single sense, the way in which temporal succession and overlap are determined is not yet established
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