free online ratings are less trustworthy than those that have some cost to them... In ecology, costly signaling theory argues that displays that “cost” more — like elaborate peacock tails, or strenuous displays of hunger from baby birds — are more likely to reflect reality... making rating goods or services as easy as possible... is counterproduct…

Asking humans to judge each other can be a surprisingly powerful thing... But invoking a sense of being watched isn’t the only way platforms subliminally encourage social behaviour... persuasive design: if you want people to do something, don’t explain why, just show them how... If extremists seek to spread fear and shock, counterspeech might aim…