Gottlieb G
Dev Psychobiol. 1982 Nov;15(6):507-17. doi: 10.1002/dev.420150603.
The domestic mallard duck embryo must be exposed to its embryonic contract-contentment call at a repetition rate of 4 notes/sec if the neonate is to show the species-typical preference for the maternal call at its normal rate (3.7 notes/sec) after hatching. Exposing the embryo to the contact call at either 2.1 notes/sec or 5.8 notes/sec is no more effective than no auditory experience at all. To determine if there is a critical period for exposure, embryos were exposed to the 4 notes/sec call either before or after hatching. Both periods proved equally effective provided only that a 48-hr "consolidation" period was allowed to intervene between stimulation and testing. That is, the birds tested 24 hr after prenatal or postnatal stimulation behaved as if they were not stimulated at all. The present study was undertaken to determine whether the curious requirement for a consolidation period is a normal developmental phenomenon or a consequence of limiting the birds to exposure to a call with an abnormally invariant repetition rate of 4 notes/sec. To that end, embryos were stimulated with the same call as before but at variable rates of 2.1, 4, and 5.8 notes/sec, as happens under normal conditions of development. In this case, the neonates had no need for a consolidation period and showed the species-typical preference at 24 hr after hatching. Thus the previous results were a consequence of an abnormally narrow range of embryonic auditory stimulation. A 2nd experiment showed that, if the birds' postnatal perception was to be normal, the embryos could not be merely exposed to the rhythmic component of the contact call, but had to experience the characteristic frequency modulation of the call as well. These results indicate that we require surprisingly detailed information about the sensory stimulation present during the usual course of development of our subject species if we are to give an appropriate interpretation to the results of early experiential and critical period manipulations. Knowledge of usual sensory-stimulative variations has not been a conspicuous feature of developmental psychobiological studies in the past.
如果新生绿头鸭要在孵化后以正常速率（3.7次/秒）表现出对母鸭叫声的物种典型偏好，那么其胚胎必须以4次/秒的重复速率接触其胚胎期的接触满足叫声。以2.1次/秒或5.8次/秒的速率让胚胎接触接触叫声，其效果并不比完全没有听觉体验更好。为了确定是否存在接触的关键期，在孵化前或孵化后让胚胎接触4次/秒的叫声。结果证明，只要在刺激和测试之间有一个48小时的“巩固”期，这两个时期的效果是一样的。也就是说，在产前或产后刺激24小时后进行测试的幼鸟，表现得就好像它们根本没有受到刺激一样。本研究旨在确定对巩固期的这种奇特要求是一种正常的发育现象，还是将幼鸟限制在接触重复速率异常恒定为4次/秒的叫声的结果。为此，像之前一样用相同的叫声刺激胚胎，但速率分别为2.1次/秒、4次/秒和5.8次/秒，这是在正常发育条件下会出现的情况。在这种情况下，新生幼鸟不需要巩固期，并且在孵化后24小时就表现出了物种典型偏好。因此，之前的结果是胚胎听觉刺激范围异常狭窄的结果。第二个实验表明，如果幼鸟出生后的感知要正常，胚胎不仅要接触接触叫声的节奏成分，还必须体验叫声的特征频率调制。这些结果表明，如果我们要对早期经验和关键期操作的结果给出恰当解释，就需要关于我们研究对象物种正常发育过程中存在的感觉刺激的惊人详细信息。过去，对正常感觉刺激变化的了解并不是发育心理生物学研究的显著特征。
