Watching fights raises fish hormone levels.

Reports on research to determine whether the so-called challenge hypothesis can be extended to bystanders. Statement that an individual's androgen production responds to their social interactions with other group members; Measurement of the concentrations of testosterone and 11-ketotestosterone in adult male cichlid fish; Production of an androgen surge in spectators; Conclusion that androgens may eventually be viewed not only as sex steroids but also as competition hormones.