productivity

You exert less effort when you are not alone.

A 1913 study found that individuals pulling on a rope in a group exert less force than when pulling individually.

This is social loafing. As group size increases, the individual sense of accountability diminishes, leading to lower contribution per person.

Your output is often calibrated to the anonymity provided by the group.

Where this comes from

Study: Ringelmann, 1913
What the check found: The claim accurately reports the 1913 publication of Ringelmann's findings on group rope-pulling efficiency.
Confidence: Well replicated

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