HERRNSTEIN R J
J Exp Anal Behav. 1964 Jan;7(1):27-36. doi: 10.1901/jeab.1964.7-27.
Four pigeons were trained to peck at either of two response-keys. Pecking at either key occasionally produced a secondary reinforcer. Then, in the presence of the secondary reinforcer, further pecking occasionally produced the primary reinforcer, food. The relative rate at which each pigeon pecked to obtain a secondary reinforcer equalled the relative rate of primary reinforcement in its presence.
训练了四只鸽子去啄两个反应键中的任意一个。偶尔啄其中任何一个键都会产生一个次级强化物。然后,在次级强化物出现的情况下,进一步的啄击偶尔会产生初级强化物——食物。每只鸽子为获得次级强化物而啄击的相对速率与其出现时初级强化的相对速率相等。