It is said every three to four years millions of lemmings on the Scandinavian Peninsula jump into the sea in acts of collective suicide. Originally it was though this behavior could be explained by genetic programming, but research then revealed a high level of correlation between the number of lemmings and the timing of the group suicides. Further work indicated that this was the product of "social psychology."
話說斯堪地那維亞半島上的老鼠，三、四年會投海自殺幾千萬隻，人們原以為是基因作祟，後來發現鼠口比例和自殺時間有高度吻合性，研究結果是「社會心理」造成的。