A learning curve drawn by a pen that moves across a roll of paper at a steady rate, increasing its vertical height by a fixed amount for every response of an organism, such as a lever press by a rat in a Skinner box or a peck by a pigeon of an illuminated plastic key (see illustration). To prevent the curve rising off the top of the paper, the pen resets instantly to the bottom of the paper whenever it approaches the top. The slope of the curve within a specified region indicates the rate of responding at that time. It was invented by the US psychologist B(urrhus) F(rederic) Skinner (1904–90) while he was a postgraduate student at Harvard University in the late 1920s. See also learning curve, operant conditioning, reinforcement (1). cumulative recorder n. A device for producing a cumulative record. [So called because it represents a cumulative distribution of responses]
Cumulative record. A segment of a typical cumulative record, showing a declining rate of responding. The small check marks sloping down to the right indicate reinforcements.