Dougherty D M, Lewis P
Department of Psychology, Ohio University, Athens 45701.
J Exp Anal Behav. 1991 Jul;56(1):97-104. doi: 10.1901/jeab.1991.56-97.
Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.
刺激泛化、辨别学习和峰值转移。九个实心黑色圆圈作为刺激物，大小从0.5英寸到4.5英寸（1.3厘米到11.4厘米）不等。每匹马通过连续接近法进行训练，使其在出现正性刺激物（2.5英寸[6.4厘米]的圆圈）时用嘴唇按压鼠用杠杆。训练进展迅速，与其他实验动物的情况相当。在以30秒可变间隔时间表维持反应后，在辨别训练之前从2匹马收集刺激泛化梯度。在辨别训练期间，在正性刺激物（2.5英寸的圆圈）出现时，按压杠杆后会得到谷物，而在负性刺激物（1.5英寸[3.8厘米]的圆圈）出现时，按压杠杆后则永远不会得到谷物。三匹马在少于15次训练中达到了对负性刺激物零反应的标准。在辨别训练之前接受刺激泛化测试的马产生对称梯度；在泛化测试之前接受辨别训练的马产生不对称梯度。这些梯度的峰值从负性刺激物处移开。这些结果与在其他动物中观察到的辨别、刺激泛化和峰值转移现象一致。
