Spetch M L, Belke T W, Barnet R C, Dunn R, Pierce W D
Department of Psychology, University of Alberta, Edmonton, Canada.
J Exp Anal Behav. 1990 Mar;53(2):219-34. doi: 10.1901/jeab.1990.53-219.
Pigeons' choice between reliable (100%) and unreliable (50%) reinforcement was studied using a concurrent-chains procedure. Initial links were fixed-ratio 1 schedules, and terminal links were equal fixed-time schedules. The duration of the terminal links was varied across conditions. The terminal link on the reliable side always ended in food; the terminal link on the unreliable side ended with food 50% of the time and otherwise with blackout. Different stimuli present during the 50% terminal links signaled food or blackout outcomes under signaled conditions but were uncorrelated with outcomes under unsignaled conditions. In signaled conditions, most pigeons displayed a nearly exclusive preference for the 100% alternative when terminal links were short (5 or 10 s), but with terminal links of 30 s or longer, preference for the 100% alternative was sharply reduced (often to below .5). In unsignaled conditions, most pigeons showed extreme preference for the 100% alternative with either short (5 s) or longer (30 s) terminal links. Thus, pigeons' choice between reliable and unreliable reinforcement is influenced by both the signal conditions on the unreliable alternative and the duration of the terminal-link delay. With a long delay and signaled outcomes, many pigeons display a suboptimal tendency to choose the unreliable side.
采用并发链程序研究了鸽子在可靠（100%）和不可靠（50%）强化之间的选择。初始链为固定比率1的时间表，终端链为相等的固定时间时间表。终端链的持续时间在不同条件下有所变化。可靠一侧的终端链总是以食物结束；不可靠一侧的终端链有50%的时间以食物结束，否则以停电结束。在50%的终端链期间出现的不同刺激在有信号条件下表示食物或停电结果，但在无信号条件下与结果无关。在有信号条件下，当终端链较短（5秒或10秒）时，大多数鸽子对100%的选择表现出几乎完全的偏好，但当终端链为30秒或更长时，对100%选择的偏好急剧下降（通常降至0.5以下）。在无信号条件下，大多数鸽子对终端链较短（5秒）或较长（30秒）的100%选择都表现出极端偏好。因此，鸽子在可靠和不可靠强化之间的选择受到不可靠选择上的信号条件以及终端链延迟持续时间的影响。在长时间延迟和有信号结果的情况下，许多鸽子表现出选择不可靠一侧的次优倾向。
