Smith Tracy T, McLean Anthony P, Shull Richard L, Hughes Christine E, Pitts Raymond C
University of North Carolina, Wilmington.
J Exp Anal Behav. 2014 Jul;102(1):102-25. doi: 10.1002/jeab.90. Epub 2014 May 26.
Log-survivor analyses of interresponse times suggest that the behavior of rats responding under single variable-interval schedules is organized into bouts (i.e., periods of engagement and disengagement). Attempts to generalize this analysis to the key pecking in pigeons, however, have failed to produce the characteristic broken-stick appearance typically obtained with rats. This failure may be due to a relatively low rate of reinforcement for engaging in alternative behavior experienced by pigeons. The present study tested this hypothesis by exposing four pigeons to concurrent schedules of reinforcement for key pecking, first without a changeover delay (COD) and then with a COD. In this arrangement, one of the concurrent options was treated as the target response and the rate of reinforcement for that option was manipulated across conditions. The other option provided explicit reinforcement for engaging in an alternative response (i.e., explicit reinforcement for disengaging from the target response). In the absence of a COD, log-survivor plots for three of the pigeons were approximately linear, thus providing no evidence that responding was organized into bouts. When a COD was present, plots were broken stick in appearance, indicating a bout structure had been generated in the pigeons' behavior. Both bout length and the rate of bout initiations were a function of differences in rate of reinforcement. These data suggest that behavior may become organized into bouts when contingencies create sufficiently long visits to both the target behavior and the extraneous behavior. Fits of a double-exponential model deviated systematically from the actual plots due to the presence of a plateau between the two limbs. An alternative, double-gamma, model was explored, and it provided a considerably better fit than did the double-exponential.
对反应间隔时间的对数生存分析表明，在单一可变间隔时间表下做出反应的大鼠的行为被组织成一个个回合（即参与和脱离的时间段）。然而，试图将这种分析推广到鸽子的按键啄击行为上，却未能产生通常在大鼠身上获得的典型的折断棍棒状图形。这种失败可能是由于鸽子参与替代行为时的强化率相对较低。本研究通过让四只鸽子接受按键啄击的并发强化时间表来检验这一假设，首先没有转换延迟（COD），然后有COD。在这种安排中，并发选项之一被视为目标反应，并且该选项的强化率在不同条件下进行操纵。另一个选项为参与替代反应提供明确的强化（即从目标反应中脱离的明确强化）。在没有COD的情况下，三只鸽子的对数生存图大致呈线性，因此没有证据表明反应被组织成回合。当存在COD时，图呈现出折断棍棒状，表明鸽子的行为中产生了回合结构。回合长度和回合启动率都是强化率差异的函数。这些数据表明，当意外情况导致对目标行为和无关行为的访问时间足够长时，行为可能会被组织成回合。由于在两个分支之间存在一个平稳期，双指数模型的拟合与实际图有系统偏差。探索了一种替代的双伽马模型，它比双指数模型提供了更好的拟合。
