Machado A
Department of Psychology, Duke University, Durham, North Carolina 27706.
J Exp Anal Behav. 1992 Sep;58(2):241-63. doi: 10.1901/jeab.1992.58-241.
In Experiment 1, two conditions were compared: (a) a variability schedule in which food reinforcement was delivered for the fourth peck in a sequence that differed from the preceding N four-peck sequences, with the value of N continuously adjusted to maintain reinforcement probability approximately constant; and (b) a control condition in which the variability constraint was dropped but reinforcement probability remained constant. Pigeons responded approximately randomly under the variability schedule but showed strong stereotyped behavior under the control condition. Experiments 2 and 3 tested the idea that variability is the outcome of a type of frequency-dependent selection, namely differential reinforcement of infrequent behavior patterns. The results showed that pigeons alternate when frequency-dependent selection is applied to single pecks because alternation is an easy-to-learn stable pattern that satisfies the frequency-dependent condition. Nevertheless, 2 of 4 pigeons showed random behavior when frequency-dependent selection was applied to two pecks, even though double alternation is a permissible and stable stereotype under these conditions. It appears that random behavior results when pigeons are unable to acquire the stable stereotyped behavior under a given frequency-dependent schedule.
在实验1中，比较了两种条件：(a) 一种变化性程序，在该程序中，食物强化是在与之前的N个四啄序列不同的序列中的第四次啄击时给予的，N的值不断调整以保持强化概率大致恒定；(b) 一个对照条件，在该条件下，变化性约束被取消，但强化概率保持恒定。鸽子在变化性程序下的反应大致是随机的，但在对照条件下表现出强烈的刻板行为。实验2和3检验了这样一种观点，即变化性是一种频率依赖选择的结果，即对不频繁行为模式的差别强化。结果表明，当频率依赖选择应用于单次啄击时，鸽子会交替，因为交替是一种易于学习的稳定模式，满足频率依赖条件。然而，当频率依赖选择应用于两次啄击时，4只鸽子中有2只表现出随机行为，尽管在这些条件下双交替是一种允许的和稳定的刻板行为。当鸽子在给定的频率依赖程序下无法获得稳定的刻板行为时，似乎就会出现随机行为。
