In the 1970s, Nottebohm and Arnold reported marked male-biased sex differences in the volume of three song control nuclei in songbirds. Subsequently a series of studies on several songbird species suggested that there is a positive correlation between the degree to which there is a sex difference in the volume of these song control nuclei and in song behavior. This correlation has been questioned in recent years. Furthermore, it has become clear that the song circuit is fully integrated into a more comprehensive neural circuit that regulates multiple courtship and reproductive behaviors including song. Sex differences in songbirds should be evaluated in the context of the full complement of behaviors produced by both sexes in relation to reproduction and based on the entire circuit in order to understand the functional significance of variation between males and females in brain and behavior. Variation in brain and behavior exhibited among living songbird species provides an excellent opportunity to understand the functional significance of sex differences related to social behaviors.

在 1970 年代，Nottebohm 和 Arnold 报告了鸣禽中三个鸣叫控制核的音量存在显着的男性偏向性别差异。随后对几种鸣禽物种进行的一系列研究表明，这些鸣叫控制核的数量存在性别差异的程度与鸣叫行为之间存在正相关关系。这种相关性近年来受到质疑。此外，很明显，歌曲回路完全集成到一个更全面的神经回路中，该回路调节包括歌曲在内的多种求偶和生殖行为。鸣禽的性别差异应在两性产生的与繁殖相关的行为的完整补充的背景下进行评估，并基于整个回路，以了解雄性和雌性之间大脑和行为变异的功能意义。现存鸣禽物种中表现出的大脑和行为的变化为了解与社会行为相关的性别差异的功能意义提供了绝佳的机会。