Analog robot
An analog robot is a type of robot which uses analog circuitry to go toward a simple goal such as finding more light or responding to sound. The first real analog robot was invented in the 1940s by William Grey Walter. The name of these robots were ELSIE and ELMER (Electro Mechanical Robot). The original circuitry was developed using two vacuum tubes and a photocell to search and follow a light. Recently a kind of analog robots was developed by Mark Tilden.
Social robot
While robots have often been described as possessing social qualities (see for example the tortoises developed by William Grey Walter in the 1950s), social robotics is a fairly recent branch of robotics. Since the early 1990s artificial intelligence and robotics researchers have developed robots which explicitly engage on a social level. Notable researchers include Cynthia Breazeal, Tony Belpaeme, Aude Billard, Kerstin Dautenhahn, Yiannis Demiris, Hiroshi Ishiguro, Maja Mataric, Javier Movellan, Brian Scassellati and Dean Weber. Also related is the Kansai engineering movement in Japanese science and technology --- for social robotics, see especially work by Takayuki Kanda, Hideki Kozima, Hiroshi Ishiguro, Micho Okada, Tomio Watanabe, and P. Ravindra S. De Silva.