(a) Sample images from the BSDS data set. Images of animals, human faces, landscapes, buildings, and so on are used. (b) Sliding window on images from the BSDS data set so that the appearance of movement is achieved. Shown by the red arrow is how much the window has moved from frame 1 to frame 4. In general, movement of sliding window is random and in any direction, but we focus on horizontal movement in the case of natural videos. (c) Images of horizontal and vertical bars (above) and how the bars move in videos (below). (d) Eighteen filters: ON, OFF, ON/OFF with two gaussian subfields, different subfields dominating, at different intensities and orientations. Color bars show the different intensities of pixels. (e) Example of a spatiotemporal filter comprising two frames. Spatiotemporal filters are added to the 18 original filters to make up a total of 34 filters. The filter shown here over two frames captures a $45deg$ bar moving to the left and is obtained by translating the original filter by three pixels. Color bars show the different intensities of pixels to the left. (f) Two filters for the simplistic “bar world” comprising a horizontal and a vertical bar, respectively.