bystander effect

The presence of more people makes you less helpful.

Darley and Latané (1968) found participants were 85% likely to help a person in need when alone, and 31% when four others were present.

Change 80% to 85% to match the primary study data.

Your readiness to help is often tethered to what the crowd decides is necessary.

Where this comes from

Study: Darley and Latané (1968)
What the check found: The figures are slightly inaccurate; the original study reported 85% helping when alone, not 80%. The 31% figure for the group condition is accurate.
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.