Left visual field attentional advantage in judging simultaneity and temporal order.

Dynamic environments often contain features that vary simultaneously as well as features that vary sequentially. In principle, the correspondingly distinct sensations of simultaneity and temporal order could arise from a single shared neural computation that involves differencing two arrival times. On the other hand, simultaneity judgments (SJs) and temporal order judgments (TOJs) have distinct informational requirements that could be optimized by distinct neural events. To explore overlap in the neural events mediating SJs and TOJs, the present experiments built on recent reports that SJ precision in the left visual field (LVF) exceeds that in the right visual field (RVF). Participants completed divided attention tasks requiring either SJs or TOJs to LVF or RVF targets. SJs exhibited a significant LVF advantage, as expected. TOJs also exhibited a significant LVF advantage. Specifically, simply repositioning targets from the LVF to the RVF generated mean TOJ threshold increases (temporal precision reductions) between 39% and 57%, an effect size equivalent to approximately two LVF detectors for each RVF detector. Control experiments indicated that this LVF advantage reflected the temporal resolution of visual attention, rather than lower-level flicker discrimination or masking. These findings constitute additional evidence for an LVF advantage in time-sensitive attentional tasks and further contradict our subjective experience of homogenous temporal precision across the visual field.