Science. 1973 Aug 31;181(4102):875-7. doi: 10.1126/science.181.4102.875.
In a cooled chamber, chicks approached and pecked a small disk whose illumination preceded heat lamp activation, even when pecks prevented heat lamp onset. These behaviors did not occur when the disk and heat stimuli were randomly presented. Approach and contact of conditioned stimuli may develop even though these behaviors are not (i) evoked by the reinforcing stimulus, (ii) necessary for reinforcer reception, or (iii) ever followed by the reinforcer.
在一个冷却的房间里，小鸡会接近并啄一个小圆盘，即使啄食阻止了热灯的开启，这个小圆盘的照明也会先于热灯的激活。当圆盘和热刺激随机呈现时，这些行为不会发生。即使这些行为 (i) 不是由强化刺激引起的，(ii) 不是获得强化物所必需的，或者 (iii) 从未被强化物跟随，条件刺激的接近和接触也可能发展。
