GROUP FORMATION AND INTRUDER PARADIGMS 
Behavioral research can involve the study of the formation of new social relationships or the 
effects of introduction of a new individual into an established social group or territory. When 
humanely employed, these procedures have been effective in studying aggressive behavior and 
the behavioral responses to stress (Miczek, 1979; Miczek and O'Donnell, 1978). Evidence of 
serious wounds or an inability to maintain normal homeostatic functions should be used as 
criteria for terminating the research condition. Aggression may be the primary focus of the 
research (Boccia et al., 1989), may be a useful by-product (e.g., alpha animal using titrated 
aggression in the social control of other animals), or may be an unwanted by-product of social 
manipulation (e.g., in formation of primate social groups). 
SOCIAL SEPARATION OR ISOLATION 
While the formation of new social relationships is potentially stressful, the dissolution of 
established relationships can be equally important. Separation techniques are used to study 
the effects of loss, or disruption of social attachment bonds/relationships. These paradigms 
have served as animal models of depression, of the effects of social relationships on behavior 
and biology, and of long-term effects of early separation or loss experiences on later 
development. 
Species that exhibit “aunting” behavior (sharing of infants by adults) may be associated with 
less marked infant responses to separation. Langurs, for example (Dolhinow, 1980), exhibit 
relatively little distress when separated from their natal mothers and adopted by other adult 
females within the group. Similarly, adult female bonnet macaques (M. radiata) will 
frequently share care of young infants, such that the infants develop close bonds with adult 
females in addition to the mother. When the mother is removed from the infant in these 
groups, and the infants remain in the social group with familiar adults with whom they have 
established a previous relationship, the separation response is muted both behaviorally and 
physiologically (Laudenslager et al., 1990; Reite et al., 1989). With rodents, methods for 
cross-fostering of pups are routinely used. 
SOCIAL DEPRIVATION 
Research involving prolonged social isolation, particularly of young animals, may be 
evaluated depending on whether the isolation is required as a specific focus of the research, a 
necessary corollary of the research protocol, or an inadvertent occurrence based on practical or 
husbandry considerations. Where separation or social isolation is the subject of the research, 
the justification of separation must draw upon the considerable knowledge that has been 
gained from this type of research. Manipulations of the early rearing environment of animals 
have provided important insights into the development of social and affective behaviors, as 
well as sensory functions. This area of research has also provided convincing support for the 
role of the parent in promoting normal cognitive and emotional development. 
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