Grace R C, Nevin J A
Department of Psychology, University of Canterbury, Private Bag 4800, Christchurch, New Zealand; University of New Hampshire, Durham, NH 03824, USA.
Behav Processes. 1999 Apr;45(1-3):115-27. doi: 10.1016/s0376-6357(99)00013-3.
To investigate the role of timing processes in choice, we used a new procedure that provided simultaneous measures of ongoing choice and timing behavior. Pigeons responded in a peak procedure in which the delays to reinforcement signaled by red and green center-key stimuli were 10 and 20, or 20 and 40 s. After 25 sessions of training, the peak procedure was embedded within concurrent chains: The inter-trial interval was replaced by a choice phase in which the two side keys were illuminated white; responses to the left and right keys occasionally changed the center-key to red or green, respectively; and the terminal links signaled by the center-key stimuli were identical to the trials of the peak procedure. The temporal control of responding on no-food trials was the same regardless of whether the no-food trials occurred in the peak procedure or as the terminal links of concurrent chains. After an intervening condition with the peak procedure in which the delay for the 10 s stimulus was changed to 40 s (or vice versa), the pigeons were returned to concurrent chains. Choice responding did not reflect the changed delay, despite the fact that the pigeons timed the delays in both terminal links accurately as indexed by responding on no-food trials. This result challenges current accounts of choice based on timing processes, such as scalar expectancy theory, which assume that choice responding is mediated by a representation of terminal link delays to reinforcement. Apparently, pigeons' choice and timing behavior in a single session can be controlled by temporal information from different temporal epochs.
为了研究时间进程在选择行为中的作用，我们采用了一种新的程序，该程序能同时测量正在进行的选择行为和时间行为。鸽子在一个峰值程序中做出反应，其中红色和绿色中央按键刺激所指示的强化延迟分别为10秒和20秒，或20秒和40秒。经过25节训练课程后，峰值程序被嵌入到并发链中：试验间隔被一个选择阶段所取代，在此阶段，两个侧键被照亮为白色；对左键和右键的反应偶尔会分别将中央按键变为红色或绿色；由中央按键刺激所指示的终端链与峰值程序的试验相同。无论无食物试验是出现在峰值程序中还是作为并发链的终端链，在无食物试验中反应的时间控制都是相同的。在一个中间条件下，峰值程序中10秒刺激的延迟被改为40秒（反之亦然），之后鸽子被放回并发链中。尽管鸽子在无食物试验中的反应表明它们能准确地对两个终端链中的延迟进行计时，但选择反应并未反映出延迟的变化。这一结果对当前基于时间进程的选择理论提出了挑战，比如标量期望理论，该理论假设选择反应是由终端链到强化的延迟表征所介导的。显然，鸽子在单个实验中的选择和时间行为可以由来自不同时间阶段的时间信息所控制。
