Gottlieb G
Dev Psychobiol. 1987 Jul;20(4):393-404. doi: 10.1002/dev.420200404.
The present experiments sought to determine the relationship of the malleable period--when the mallard duck embryo is most susceptible to alien forms of maternal auditory stimulation--to the critical period, when the embryo must hear its own vocalizations in order to respond normally to the species-typical maternal call after hatching. It was found that a preference for either a wood duck or a chicken maternal call could be induced in devocalized mallard duck embryos by exposing them to either alien call some time between day 24, 0600 to day 26, 0600 hrs. Further experiments showed the height of the malleable period to be between day 24, 1400 hrs and day 25, 0800 hrs of embryonic development. Since the embryonic critical period for maintenance of the species-typical maternal auditory preference spans day 24, 0800 hrs to day 26, 0800 hrs, the malleable period for the induction of a preference for species-atypical maternal stimulation falls inside the critical period. While it is often assumed that malleable and critical periods overlap, this is the first behavioral study to actually demonstrate the temporal relationship of the two periods. It would seem important to further examine malleable and critical periods of development in a broader array of developmental contexts and species to determine whether malleable periods for atypical or abnormal development and critical periods for species-typical or normal development always coincide.
本实验旨在确定可塑性期（即野鸭胚胎对母体听觉刺激的异源形式最敏感的时期）与关键期之间的关系，在关键期胚胎必须听到自己的叫声，以便在孵化后对物种典型的母体叫声做出正常反应。研究发现，在24日06:00至26日06:00之间的某个时间将去声的野鸭胚胎暴露于异源叫声中，可以诱导它们对林鸳鸯或母鸡的母体叫声产生偏好。进一步的实验表明，可塑性期的高峰期在胚胎发育的24日14:00至25日08:00之间。由于维持物种典型母体听觉偏好的胚胎关键期跨越24日08:00至26日08:00，诱导对物种非典型母体刺激偏好的可塑性期落在关键期内。虽然人们通常认为可塑性期和关键期会重叠，但这是第一项实际证明这两个时期时间关系的行为研究。在更广泛的发育背景和物种中进一步研究发育的可塑性期和关键期，以确定非典型或异常发育的可塑性期与物种典型或正常发育的关键期是否总是重合，这似乎很重要。
