Figure 5: Stanford's Cart and SRI's Shakey: The "Stanford Cart" (a) and SRI's "Shakey" (b) were the first mobile robots to be controlled by computers (large mainframes doing about a quarter million calculations per second, linked to the robots by radio). Both used television cameras to see. The Cart could follow white lines quite reliably, Shakey could find large prismatic objects somewhat less reliably. Their control complexity was far greater than Elsie's or the Beast's (lines can be tracked using simple Elsie-like techniques with ground-mounted lights and photocells, but it takes complex adaptation and prediction to do it with ambient light from a high vantage point), and the use of computers to control robots can be compared to the advent of multicellular animals with nervous systems in the Cambrian explosion: both events blew the lid on behavioral complexity in their respective domains.