Short answer
Leave did win the engagement battle, but the evidence does not support the claim that it did so by being more negative. Pages aligned with Leave produced 65% of the engagement from 23% of the posts, yet among campaigns, leaders and parties, Remain posts were, if anything, slightly more often negative.
What the evidence shows
- The study covers 17,657 posts from 92 UK pages between 20 February and 23 June 2016, which drew 33.5 million interactions.
- Most of Leave's lead came from four large pages: Leave.EU, Vote Leave, Nigel Farage and UKIP. It shrinks but stays positive when audience size is held constant.
- After correcting the dictionary measure, 37% of Leave posts and 42% of Remain posts were negative among campaigns, leaders and parties (difference -5 points, 95% CI -19 to +8).
- Leave pages focused more on immigration (17% against 5%) and British national identity.
- Negative posts drew more engagement on both sides.
Caveats
The negativity correction relies on a validation sample coded by an AI model from a written codebook. The uncertainty around the difference between the sides is wide.