Temporal summation of global form signals in dynamic Glass patterns

•Dynamic Glass patterns are better detected compared to static Glass patterns.•Dynamic differs from static in temporal frequency and number of unique frames.•Number of unique frames was found to be the dominant factor in reducing threshold.•The advantage for dynamic Glass pattern may be due to summation of form signals.

The ability to perceive complex objects in the environment requires that the visual system integrate local form information into global shapes. Glass patterns (GPs) are stimuli that are commonly used to study this integration process. GPs consist of randomly positioned dot-pairs oriented in a coherent way to create a global form. When multiple GPs are presented sequentially, observers report a percept of illusory coherent motion and have lower detection thresholds relative to a single presentation GPs. The percept of illusory motion has been attributed to the visual system interpreting the dot-pairs in GPs as motion streaks. However, it remains unclear why dynamic GPs are detected at lower thresholds than static GPs. Two main differences exist between static and dynamic GPs: (a) dynamic GPs contain multiple presentations of global form signals compared to a single presentation in static GPs and (b) dynamic GPs have a greater temporal frequency than static GPs. Here we investigated which of these two factors contributed to the heightened sensitivities for dynamic GPs. We systematically varied the number of unique GPs and the rate at which each unique frame is presented (i.e., temporal frequency). The results show that, within the range of temporal frequency used, the primary influence on detection thresholds was the number of unique frames. These results suggest that the improved detection sensitivities can be driven by a mechanism of temporal summation of global form.