具有攻擊性的個體通常較為勇敢，並傾向主動探索陌生的環境，同時有比較好的學習表現。這種不同個體間呈現出相似之行為間的相關性被稱之為行為群（behavioral syndrome）。前人提出，這些行為之間的相關性可能來自於這些行為受到相似的生理機制的影響；例如，一種荷爾蒙同時調控兩種以上的行為，而使得這些行為呈現彼此相關的現象。本篇測量Kryptolebias marmortus的攻擊性與勇敢程度、探索傾向以及學習表現之間的相關性。同時藉由強制給予一次落敗／獲勝經驗改變個體的攻擊性，來探討這些行為與攻擊性之間的相關性是否會受到前次打鬥經驗所影響而改變。本篇研究藉由測量個體的各個行為和睪固酮以及皮質醇濃度之間的相關性，來探討這些行為的相關性是否可能源自於它們皆受到此二荷爾蒙的調控而引起。實驗結果發現，個體的攻擊性與勇敢程度成正相關，而攻擊性和探索傾向以及學習表現之間則沒有顯著的相關性。實驗同時發現，個體的攻擊性與勇敢程度之間的相關性並不會受到前次打鬥經驗所影響。除此之外，個體的攻擊性以及勇敢程度皆與睪固酮基礎值成正相關。這些結果顯示攻擊性－勇敢程度行為群穩定存在於K. marmortus個體中，而此二行為的相關性可能源自於它們皆受到睪固酮基礎值所調控。

Aggressive individuals are usually also bold, actively explore their environment and perform better in learning tasks. A suite of correlated behaviors reflecting between-individual consistency in behavior across multiple situations is termed a ‘behavioral syndrome’. Researchers have suggested that a possible cause for the correlation between different behaviors might lie in the neuroendocrine system. In this study, I examined the relationship between aggressiveness and each of boldness, exploratory tendency and learning performance in a mangrove killifish, Kryptolebias marmoratus. I tested the stability of the relationships by altering individuals’ aggressiveness with a recent winning or losing experience. I also explored the possibility that the relationships arise because these behaviors are modulated by similar physiological mechanisms (i.e. levels of cortisol and testosterone). The results showed that aggressiveness was positively correlated with boldness but not with exploratory tendency or learning performance. Recent contest experience influenced individuals’ aggressiveness, tendency to explore and learning performance but not their boldness. Contest experience did not, however, influence the relationship between aggressiveness and boldness, both of which were positively correlated with baseline testosterone levels. The results suggest a stable aggressiveness-boldness syndrome in K. marmoratus and that baseline testosterone level might be involved in mediating this relationship.

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