 Social group

In animal behaviour, a social group is a set of animals whose association and interactions are studied as a unit. Its operational definition specifies membership, the observation period and what counts as association. Sharing a location once need not establish persistent affiliation, and a group assembled for an experiment need not represent every naturally occurring grouping.

Group structure includes more than social group size. With $n$ members, there are $n(n-1)/2$ possible unordered pairs. A group of four therefore permits six distinct pairs, whereas a group of ten permits 45. These are possible relationships, not observations that every pair actually interacts. Recording which animals associate preserves information that a headcount discards.

Group membership also affects experimental interpretation. A study of neophobia compared 70 Bengalese finches in seven groups with 58 white-rumped munias in six groups. Feeding responses were recorded under familiar and novel-object conditions.^[ref] The counts of birds and groups describe different levels of replication. If animals share a setting and influence one another, treating every bird as an independent replicate of a group-level treatment risks pseudoreplication. The appropriate experimental unit follows the treatment assignment and measurement design, rather than simply the largest available count.