早期生活環境之差異，可導致腦發展之差異。本實驗之目的，在於探討老鼠斷奶後，那一段時間內的環境影響最大。先求造成腦差異時所需的最低環境操弄量；結果發現三十天的環境差別操弄，每天三小時，乃是最低需要量。再求關鍵期，結果發現在斷奶後四十五天內，所謂的「關鍵期」並不存在。

　　　　　The effect of early experience on brain development has been well demonstrated by the Berkeley group. In the present experiment, two questions were asked: First, the leastamount of environmental manipulation time necessary for producing differential brain development: Second, the critical period of the environmental influence on the brain. It wasfound that 30 days, 2 hours a day is the answer for the first question, and absence of critical period for the second.