Explanation:

- Co-operation: Primary groups are characterized by close, personal relationships where members support and cooperate with one another. These groups often include family and close friends.

- Economic efficiency: Primary groups are not typically focused on economic efficiency. Instead, they prioritize emotional bonds and mutual support rather than economic or productivity goals.

- Emotional involvement: Members of a primary group are deeply emotionally involved with each other. These groups often fulfill emotional and psychological needs.

- Group Identity: A strong sense of belonging and shared identity is a hallmark of primary groups. Members often see themselves as part of a close-knit unit.

Economic efficiency is indeed not a typical feature of primary groups, as these groups focus on emotional connections rather than economic goals.