Gipson Cassandra D, Miller Holly C, Alessandri Jérôme J D, Zentall Thomas R
University of Kentucky, Lexington, KY 40506, United States.
Behav Processes. 2009 Oct;82(2):126-32. doi: 10.1016/j.beproc.2009.05.006. Epub 2009 Jul 14.
There is evidence that pigeons prefer conditioned reinforcers that are preceded by greater effort over those that are preceded by less effort (an effect that has been attributed to within-trial contrast). In past research the probability of reinforcement for correct choice of the conditioned reinforcer has been 100%, however, the high level of reinforcement for both alternatives in training may result in a performance ceiling when choice between those alternatives is provided on test trials. In the present study we tested this hypothesis by including a group for which the probability of reinforcement in training was only 50%. Pigeons were trained on two simultaneous discriminations, one that was preceded by a 30 peck requirement the other by a single peck requirement. On test trials, we found a significant preference for the S+ that required the greater effort in training for pigeons trained with 100% and a small but nonsignificant effect for pigeons trained with 50% reinforcement. Although the hypothesis that the within-trial contrast effect was constrained by a performance ceiling was not confirmed, we did find a reliable within-trial contrast effect with 100% reinforcement.
有证据表明，鸽子更喜欢在付出更多努力之后出现的条件强化物，而不是在付出较少努力之后出现的条件强化物（这种效应被归因于试验内对比）。在过去的研究中，正确选择条件强化物的强化概率一直是100%，然而，训练中两种选择的高强化水平可能会在测试试验中提供这两种选择时导致表现上限。在本研究中，我们通过纳入一组训练中强化概率仅为50%的鸽子来检验这一假设。鸽子接受了两种同时进行的辨别训练，一种在训练前需要30次啄击，另一种在训练前只需要单次啄击。在测试试验中，我们发现，对于接受100%强化训练的鸽子，它们显著偏好训练中需要付出更多努力的S+，而对于接受50%强化训练的鸽子，虽然有一个小但不显著的效应。虽然试验内对比效应受表现上限限制的假设未得到证实，但我们确实发现了100%强化下可靠的试验内对比效应。
