In this paper I discuss how the challenge hypothesis (Wingfield et al., 1990) influenced the development of ideas about animal personality, and describe particularly promising areas for future study at the intersection of these two topics. I argue that the challenge hypothesis influenced the study of animal personality in at least three specific ways. First, the challenge hypothesis drew attention to the ways in which the environment experienced by an organism - including the social environment - can influence biological processes internal to the organism, e.g. changes to physiology, gene expression, neuroendocrine state and epigenetic modifications. That is, the challenge hypothesis illustrated the bidirectional, dynamic relationship between hormones and (social) environments, thereby helping us to understand how behavioral variation among individuals can emerge over time. Because the paper was inspired by data collected on free living animals in natural populations, it drew behavioral ecologists' attention to this phenomenon. Second, the challenge hypothesis highlighted what became a paradigmatic example of a hormonal mechanism for a behavioral spillover, i.e. testosterone's pleiotropic effects on both territorial aggression and parental care causes aggression to "spillover" to influence parenting behavior, thereby limiting behavioral plasticity. Third, the challenge hypothesis contributed to what is now a cottage industry examining individual differences in hormone titres and their relationship with behavioral variation. I argue that one particularly promising future research direction in this area is to consider the active role of behavior and behavioral types in eliciting social interactions, including territorial challenges.

中文翻译：

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个体变异和挑战假设。

在本文中，我讨论了挑战假说（Wingfield 等，1990）如何影响有关动物个性的观念的发展，并描述了在这两个主题的交叉点上未来研究特别有前途的领域。我认为挑战假说至少在三个特定方面影响了对动物个性的研究。首先，挑战假说提请注意生物体所经历的环境（包括社会环境）可以影响生物体内部生物过程的方式，例如生理学、基因表达、神经内分泌状态和表观遗传修饰的变化。也就是说，挑战假说说明了激素和（社会）环境之间的双向动态关系，从而帮助我们了解个体之间的行为变化如何随着时间的推移而出现。由于这篇论文的灵感来自收集自然种群中自由活体动物的数据，因此引起了行为生态学家对这一现象的关注。其次，挑战假说强调了成为行为溢出的荷尔蒙机制的典型例子，即睾酮对领土侵略和父母照顾的多效作用导致侵略“溢出”影响养育行为，从而限制行为可塑性。第三，挑战假说促成了现在的家庭手工业，研究激素滴度的个体差异及其与行为变异的关系。