Significance and Consequences of Avian Vocal Development

目前的许多文献，涵盖了各种感觉模式和动物群体，重点是识别个体用来评估彼此的线索，以及这些线索的进化。这种线索既可用于同性动物之间的相互作用，也可用于异性动物之间的相互作用。动物在这些相互作用中如何感知彼此，对性状的进化具有重要意义。然而，理解动物如何使用声音线索一直受到阻碍，因为很难确定声音行为与其可能后果之间的因果关系，而不仅仅是相关性。通过利用鸣禽的发声学习能力，克鲁兹马博士将能够实验性地为不同的个体“分配”不同的发声行为。有了随机分配的线索，因此不考虑其他男性特质，假设检验就可以进行了。最初的研究将集中在沼泽鹪鹩的歌曲曲目大小上，随后将研究其他物种的其他发声行为。具有“指定行为”的个体在其他测试行为与大脑特征之间因果关系的实验中变得非常宝贵；例如，人们已经发现了鸟类的歌曲曲目大小与前脑中歌曲控制中心的体积之间的相关性，但在行为（如克鲁德斯马博士的实验中）或大脑被实验操纵之前，人们无法确定因果关系的方向。

Much current literature, covering a variety of sensory modes and animal groups, focuses on identifying cues that individuals use to assess one another and on the evolution of those cues. Such cues may be used during either interactions between animals of the same sex or interactions between animals of opposite sex. How animals perceive one another during these interactions has important implications for evolution of traits. Understanding how animals may use vocal cues has been hampered, however, by the difficulty of establishing cause and effect, rather than just correlation, between the vocal behavior and its possible consequences. By taking advantage of the vocal learning abilities of songbirds, Dr. Kroodsma will be able to experimentally "assign" different vocal behaviors to different individuals. With cues assigned at random and therefore irrespective of other male qualities, hypothesis testing can proceed. Initial studies will focus on song repertoire size in marsh wrens, and study of other vocal behaviors in other species will follow. Individuals with "assigned behaviors" become invaluable in other experiments that test for cause-and-effect relationships between behavior and brain characteristics; correlations have been discovered between song repertoire size and the volume of song control centers in the avian forebrain, for example, but until either the behavior (as in Dr. Kroodsma's experiments) or the brain is manipulated experimentally, one cannot determine the direction of causation.