Winners again win, unless they are pitted against another winner. In that case, the fights escalate and the lobsters cause extensive damage to each other. Usually the dominant or subordinate status only lasts until the animal molts. Then, if a subordinate molts first, survives, and becomes larger than the dominant, it will often become the new dominant animal. These seemingly long-term changes in status and behavior are determined by the level of two hormones known as serotonin and octopamine.
Winners have higher blood levels of serotonin, while losers have higher levels of octopamine.
If a lobster who has previously lost a fight is injected with serotonin, it becomes extremely belligerent and will attack lobsters much larger than itself. Such studies imply that aggressive behavior may have a hormonal component, and therefore, the lobster is being used as a model to better understand human aggression.