the psychologists propose that this result is related to a learned response that associates wrapped packages with happy events in life, thus evoking a happier mood.
心理学家指出此项结果与一项学术反应有关。包装纸能让人联想到生活中的快乐,而唤起更愉悦的情绪。
then he noticed that a baby who had enough to drink would refuse the milk but would still go on making the learned response with clear signs of pleasure.