Mark I Perceptron: the perceptron in hardware
In spring 1960 engineers at the Cornell Aeronautical Laboratory described the Mark I, Rosenblatt's perceptron in hardware. A retina of 20 x 20 photoresistors, 512 association units, 8 response units, and weights that were potentiometers turned by electric motors. After sixteen exposures to each letter the machine identified all 26 letters of a standard font.
Why it matters
Learning in a network got purpose-built hardware in which what had been learned was held in the positions of hundreds of potentiometers rather than in the memory of a general-purpose machine. Unlike SNARC in 1951, it was a machine built to test a theory and used for experiments in learning to recognise.
By Hay and Wightman's Research Trends article: the 400 sensory units have 16,000 possible connections on a patch board, and their links to the association units are scattered at random, so each association unit sees a random spread of points on the retina. Electromechanical parts were chosen for economy and expediency; the long time constant of the motor integrators, the authors write, could not be matched within practical bounds of availability and price. In an experiment with 30 per cent of the trainer's reinforcements deliberately wrong, both halves of the machine ended above the trainer's own accuracy. The research was sponsored by the Office of Naval Research from July 1957, with the Rome Air Development Center from 1958. In Research Trends in summer 1958 Rosenblatt wrote that a working model was scheduled for completion within the next year: the perceptron then existed as theory and as a simulation on an IBM 704. What the record does not claim: the public demonstration of 23 June 1960 that archive finding aids give, whose primary document was not read; the Mark I operators' manual (report VG-1196-G-5) could not be obtained.