To cope with the continuously incoming stream of input, the visual system has to group information across space and time. Usually, spatial and temporal grouping are investigated separately. However, recent findings revealed that these two grouping mechanisms strongly interact and should therefore be studied together rather than in isolation. Here, we show that spatio-temporal grouping is very sensitive to the spatial layout of the stimuli and that the grouping processes do not require the observer's awareness. The experimental observations are compared with outcomes of simulations with a neural network model applying low-level inhibitory and excitatory interactions. The modeling results suggest that the observed interactions between spatial and temporal grouping may take place at a relatively early stage of visual processing.