Cabanac M
Department of Physiology, Faculty of Medicine, Laval University, Quebec, QC G1K 7P4, Canada.
Jpn J Physiol. 1999 Feb;49(1):1-10. doi: 10.2170/jjphysiol.49.1.
Gentle handling of mammals (rats, mice) and lizards (Iguana), but not of frogs (Rana) and fish (Carassius), elevated the set-point for body temperature (i.e., produced an emotional fever) achieved only behaviorally in lizards. Heart rate, another detector of emotion in mammals, was also accelerated by gentle handling, from ca. 70 beats/min to ca. 110 beats/min in lizards. This tachycardia faded in about 10 min. The same handling did not significantly modify the frogs' heart rates. The absence of emotional tachycardia in frogs and its presence in lizards (as well as in mammals), together with the emotional fever exhibited by mammals and reptiles, but not by frogs or fish, would suggest that emotion emerged in the evolutionary lineage between amphibians and reptiles. Such a conclusion would imply that reptiles possess consciousness with its characteristic affective dimension, pleasure. The role of sensory pleasure in decision making was therefore verified in iguanas placed in a motivational conflict. To be able to reach a bait (lettuce), the iguanas had to leave a warm refuge, provided with standard food, and venture into a cold environment. The results showed that lettuce was not necessary to the iguanas and that they traded off the palatability of the bait against the disadvantage of the cold. Thus, the behavior of the iguanas was likely to be produced, as it is in humans, through the maximization of sensory pleasure. Altogether, these results may indicate that the first elements of mental experience emerged between amphibians and reptiles.
轻柔地对待哺乳动物（大鼠、小鼠）和蜥蜴（鬣蜥），而不是青蛙（蛙属）和鱼类（鲫鱼），会提高体温设定点（即引发情绪性发热），蜥蜴仅通过行为就能达到这一设定点。心率是哺乳动物情绪的另一个检测指标，轻柔地对待也会使其加快，蜥蜴的心率从约70次/分钟加快到约110次/分钟。这种心动过速在大约10分钟后消退。同样的处理方式并未显著改变青蛙的心率。青蛙没有情绪性心动过速，而蜥蜴（以及哺乳动物）有，再加上哺乳动物和爬行动物会出现情绪性发热，青蛙和鱼类则不会，这表明情绪出现在两栖动物和爬行动物之间的进化谱系中。这样的结论意味着爬行动物具有带有其特征性情感维度——愉悦的意识。因此，在处于动机冲突的鬣蜥身上验证了感官愉悦在决策中的作用。为了能够够到诱饵（生菜），鬣蜥必须离开提供标准食物的温暖庇护所，冒险进入寒冷的环境。结果表明，生菜对鬣蜥来说并非必需，它们在诱饵的适口性和寒冷的不利因素之间进行了权衡。因此，鬣蜥的行为很可能像人类一样，是通过感官愉悦的最大化产生的。总的来说，这些结果可能表明心理体验的最初元素出现在两栖动物和爬行动物之间。
