Previous work in quite a lot of fish species has tested inhabitants level lateralization of these shows, preferentially showing one side to their opponent. Mirrors are frequently used rather than a real opponent to study aggression in fish, yet they may disrupt the traditional sample of screen behaviour. Here, using Siamese fighting fish, Betta splendens, we compare the competitive behaviour of males to a mirror image and real opponent behind a clear barrier. As this species is a facultative air breather, we also quantify surface respiration, offering insights into underlying fight motivation. Consistent with outdated work, we found proof of inhabitants level lateralization, with a bias to existing the left side and use the left eye when facing a real opponent. Contrary to expectations, there have been no modifications in the aggressive shows to a mirror and real opponent, with valuable correlations between the behaviour in the 2 situations.