What is a key factor that encourages crowd formation?

A key factor that encourages crowd formation is the occurrence of common interest events. These events naturally draw individuals together who share similar interests, goals, or experiences, leading to the gathering of crowds. When people are motivated by shared passions, such as concerts, sports games, festivals, or social movements, they are more likely to converge in a specific location. The collective enthusiasm or desire for engagement in an event fosters a sense of belonging and community, which is a powerful catalyst for crowd behavior.

Considering the other options, legal implications, while important for managing crowds, do not actively encourage their formation. Instead, they often focus on the boundaries and regulations concerning crowd behavior. Productivity motivations may drive individuals to work collaboratively but do not typically lead to the spontaneous and diverse nature seen in crowd settings. Causal relationships do not inherently create crowd scenarios; they are more about understanding interactions rather than encouraging communal gathering. Thus, common interest events stand out as the primary factor promoting crowd formation.