CHAPTER 8 
Social Variables 
Social factors come into play in behavioral research in two ways: (1) research directed at study 
of the influence of social variables upon behavior and (2) the behavioral consequences of 
husbandry techniques. Investigation of social variables in animal subjects can be used to help 
understand human problems (e.g., separation and loss). Manipulation of social variables 
(e.g., individual housing) may be necessary for performance of other research. Both will be 
addressed below. 
SOCIAL VARIABLES AS RESEARCH TOPICS 
The individual and societal cost of atypical human behavior indicates the importance of 
research with animal models of social problems. Social behavior in many species, including 
humans, may be based in large part on social attachment, a special type of relationship 
involving recognition of and response to the individual, rather than the conspecific organism. 
First seen in the mother-infant relationship, social attachment in humans extends to peer-peer 
relationships, perhaps even to non-animate relationships, and may serve a psychobiological 
regulatory function. Paradigms involving alterations of early developmental experience can 
be used for investigation of the manner in which altered early social experience contributes to 
the development of individual, social, and parenting behavior, and for studies of the basic 
neurobiological mechanisms underlying such behaviors and behavioral pathologies. 
POPULATION DENSITY 
Manipulating the number of animals housed in a limited physical environment is one means 
of investigating the behavioral and biological effects of social stimuli. In a variety of species, 
high-density housing leads to prolonged changes in cardiovascular and immune functioning. 
Given these known effects on health and well-being, high density should be used only when 
adequately justified by research goals and should not be employed as a routine or long-term 
condition. Guidelines for housing density are shown in Tables 2.1, 2.2, and 2.3 of the ILAR 
Report (ILAR, 1996). 
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