[The sequential structures of social behavior and their developmental changes in rats bidirectionally selected for emotionality].

Eighteen colonies of Tsukuba High Emotional (THE) and 17 colonies of Low Emotional (TLE), each one composing of one female and two male rats, were reared for about two months. During this period, intruder tests and intra-colony observations were conducted once a week. Social behavior of colony residents was coded sequentially with 17 items in a microcomputer. Transitions in chi 2 tests were visualized in a tree structure. The sequential structures of social behavior were compared between two strains of rat in the course of social dominance organization. Although TLE males were more aggressive than THE males, dominant males of both strains had almost the same transition structure constructed of four common sequentially bound item-groups; alpha group (bite, lunge, aggressive groom), beta group (on-top related items), gamma group (chase, lateral display, boxing, on-back), and delta group (flight, retreat, defensive upright). beta items were found to be sequentially located after bite in alpha group. delta group was disappeared with dominance organization. But there were some differences in inter- and intra-group structures between THE and TLE.