Abstract: Dominance has been assumed to be a quality of overwhelming social importance but satisfactory definitions and measures have not been devised. As an indication of predictability of outcome of interaction between animals, it can be explained in terms of ordinary learning processes previous to and during a specific relationship. Agonistic interactions are usually determined and often initiated by the subordinate's behavior, and subordinate behavior is correlated with physiological changes, so that a subordination hierarchy is probably a more useful concept than a dominance hierarchy. Hierarchies develop in stressful conditions, especially in captivity where animals with overresponsive adrenal cortices are at a selective disadvantage. In wild groups hierarchies are tenuous or absent and stress-responsive members are probably advantageous to a group. Group defense and leadership roles are not correlated with rank, but policing is characteristic of high-ranking animals in species where it occurs. There is no evidence that formation of a hierarchy reduces aggression--hierarchies are actually associated with high rates of aggression in primate groups. There is no conclusive evidence that high ranking males have greater overall reproductive success, and an alternative hypothesis that adult males are sexually active for a relatively short stage of their lives fits existing data equally well.

Abstract: In groups of ten, indidual starlings, Sturnus vulgaris, spent significantly less time in surveillance than did individuals in smaller groups and responded more quickly than single birds to a flying model hawk. Captive starlings in flocks reduce their individual surveillance efforts, but their combined efforts still enable them to be more effective than single birds in the detection of predators. Foraging behaviour of flocks was observed by placing single starlings with groups of tricoloured blackbirds, Agelaius tricolor; the starlings reduced the time they devoted to surveillance at the same rate as if they were with other starlings.

Abstract: The limited access situation in which only one of two or more subjects can gain access to a reward during a restricted time-period is an accepted measure of dominance in the rat. This study attempts to validate the technique by establishing the relationship between individual and competitive performance in order to determine whether `priority of access' has been measured. The generality of the competitive orders is examined by altering the competitive response while retaining the same reward. In view of the data collected for both time and weight-gain measures in food and water competition it is doubtful whether the limited access competitive technique can be considered a valid measure of dominance for the laboratory rat.