Dwyer Dominic M, Lydall Emma S, Hayward Andrew J
School of Psychology, Cardiff University, Cardiff, United Kingdom.
J Exp Psychol Anim Behav Process. 2011 Apr;37(2):200-10. doi: 10.1037/a0021458.
The microstructure of rats' licking responses was analyzed to investigate both "classic" simultaneous contrast (e.g., Flaherty & Largen, 1975) and a novel discrete-trial contrast procedure where access to an 8% test solution of sucrose was preceded by a sample of either 2%, 8%, or 32% sucrose (Experiments 1 and 2, respectively). Consumption of a given concentration of sucrose was higher when consumed alongside a low rather than high concentration comparison solution (positive contrast) and consumption of a given concentration of sucrose was lower when consumed alongside a high rather than a low concentration comparison solution (negative contrast). Furthermore, positive contrast increased the size of lick clusters while negative contrast decreased the size of lick clusters. Lick cluster size has a positive monotonic relationship with the concentration of palatable solutions and so positive and negative contrasts produced changes in lick cluster size that were analogous to raising or lowering the concentration of the test solution respectively. Experiment 3 utilized the discrete-trial procedure and compared contrast between two solutions of the same type (sucrose-sucrose or maltodextrin-maltodextrin) or contrast across solutions (sucrose-maltodextrin or maltodextrin-sucrose). Contrast effects on consumption were present, but reduced in size, in the cross-solution conditions. Moreover, lick cluster sizes were not affected at all by cross-solution contrasts as they were by same-solution contrasts. These results are consistent with the idea that simultaneous contrast effects depend, at least partially, on sensory mechanisms.
分析了大鼠舔舐反应的微观结构，以研究“经典”的同时对比（例如，弗莱厄蒂和拉根，1975年）以及一种新的离散试验对比程序，在该程序中，在接触8%的蔗糖测试溶液之前，先给予2%、8%或32%的蔗糖样本（分别为实验1和实验2）。当与低浓度而非高浓度的对比溶液一起食用时，给定浓度的蔗糖消耗量更高（正对比）；当与高浓度而非低浓度的对比溶液一起食用时，给定浓度的蔗糖消耗量更低（负对比）。此外，正对比增加了舔舐簇的大小，而负对比减小了舔舐簇的大小。舔舐簇大小与可口溶液的浓度呈正单调关系，因此正对比和负对比分别产生了类似于提高或降低测试溶液浓度的舔舐簇大小变化。实验3采用离散试验程序，比较了两种相同类型溶液（蔗糖-蔗糖或麦芽糊精-麦芽糊精）之间的对比或不同溶液（蔗糖-麦芽糊精或麦芽糊精-蔗糖）之间的对比。在不同溶液条件下，对比对消耗量有影响，但影响程度减小。此外，不同溶液对比对舔舐簇大小没有任何影响，而相同溶液对比则有影响。这些结果与同时对比效应至少部分取决于感觉机制的观点一致。
