Abstract
The visual system uses not only spatial but also temporal cues to segregate objects from their background. Such temporal cues include temporal synchrony (timing of changes, e.g., temporal lag) and temporal structure (pattern of changes over time) between the figure and ground. In this study, we investigated how these two factors interacted and influenced the segregation performance. A 4-by-4 lattice composed of discs with randomly assigned contrast was used, and the temporal properties among the alternating rows or columns were the same. The participants were required to determine whether the lattice consisted of horizontal or vertical bars. Four levels of temporal frequency (2, 4, 6, 8 Hz) and various temporal lags were adopted. In Experiment 1, the temporal delay between the column/row was varied and the temporal structure was kept the same; whereas, in Experiment 2, the temporal lag was jittered, with the timing of the changes either leading or lagging so that the temporal structure was different but the temporal lag was the same locally. The results showed that the optimal correctness rate decreased with the increase of temporal frequency in Experiment 1 but not in Experiment 2; also, Experiment 2 performed better than Experiment 1 (correctness rate: 0.85, 0.95). The discrimination thresholds—defined as the midpoint between the low and high plateau—showed similar temporal lag thresholds (31.96 ms ± 0.25; 25.32 ms ± 0.42) for each frequency in both experiments. In conclusion, temporal synchrony (lag) is an important factor for temporal segmentation tasks and is determined by the absolute time difference. However, the temporal structure (Experiment 2) could facilitate the segregation performance.