Final answer:
The content of the assessment instrument should focus on interacting in group situations.
Step-by-step explanation:
When assessing social barriers to leisure involvement, the content of the assessment instrument should focus on interacting in group situations. This is because social barriers often arise when individuals struggle to participate in leisure activities due to issues with social interactions and group dynamics. By assessing an individual's ability to interact and engage with others in group settings, the assessment instrument can effectively identify and address these barriers to leisure involvement.