Machado A
University of Libson, Portugal.
J Exp Anal Behav. 1989 Sep;52(2):155-66. doi: 10.1901/jeab.1989.52-155.
The present investigation developed and tested a new percentile reinforcement schedule suited to study pattern variability, whose main feature was the relative dissociation it provided between the variability requirement defining criterional responses and overall probability of reinforcement. In a discrete-trials procedure, pigeons produced patterns of four pecks on two response keys. If the pattern emitted on the current trial differed from the N preceding patterns, reinforcement was delivered with probability mu. The schedule continuously adjusted the criterion N such that the probability of a criterional response, estimated from the subject's recent behavior, was always constant. In these circumstances, the criterion corresponded to an invariant percentile in the distribution of recent responses. Using a between-subjects design, Experiment 1 manipulated the variability requirement--the percentile--while keeping overall reinforcement probability constant. The degree of variability varied directly with the requirement. In addition, an inverse relationship existed between the requirement and within-group variance. Experiment 2 manipulated probability of reinforcement while maintaining the variability requirement constant. No consistent relationship was found between variability and reinforcement probability. A tentative hypothesis was advanced ascribing the operant conditioning of behavioral variability to a process of probability-dependent selection.
本研究开发并测试了一种适用于研究模式变异性的新百分位强化程序，其主要特点是它在定义标准反应的变异性要求与总体强化概率之间提供了相对分离。在离散试验程序中，鸽子在两个反应键上产生四次啄击的模式。如果当前试验中发出的模式与之前的N个模式不同，则以概率μ给予强化。该程序不断调整标准N，使得根据受试者近期行为估计的标准反应概率始终保持恒定。在这些情况下，标准对应于近期反应分布中的一个不变百分位。实验1采用组间设计，在保持总体强化概率不变的同时，操纵变异性要求——百分位。变异性程度随要求直接变化。此外，要求与组内方差之间存在反比关系。实验2在保持变异性要求不变的同时，操纵强化概率。未发现变异性与强化概率之间存在一致关系。提出了一个初步假设，将行为变异性的操作性条件作用归因于概率依赖选择过程。
