We report the first direct comparisons of multiple alternative social media algorithms on multiple platforms on outcomes of societal interest. We used a browser extension to modify which posts were shown to desktop social media users, randomly assigning 9,386 users to a control group or one of five alternative ranking algorithms which simultaneously altered content across three platforms for six months during the US 2024 presidential election. This reduced our preregistered index of affective polarization by an average of 0.03 standard deviations (p < 0.05), including a 1.5 degree decrease in differences between the 100 point inparty and outparty feeling thermometers. We saw reductions in active use time for Facebook (-0.37 min/day) and Reddit (-0.2 min/day), but an increase of 0.32 min/day (p < 0.01) for X/Twitter. We saw an increase in reports of negative social media experiences but found no effects on well-being, news knowledge, outgroup empathy, perceptions of and support for partisan violence. This implies that bridging content can improve some societal outcomes without necessarily conflicting with the engagement-driven business model of social media.

翻译：我们报告了在多个平台上首次对多种替代性社交媒体算法在社会关注结果上的直接比较。通过浏览器扩展程序修改桌面端社交媒体用户所见帖子，我们在2024年美国总统大选期间，将9386名用户随机分配到对照组或五种替代排名算法中的一种，这些算法在六个月内同时改变三个平台的内容展示。这使我们的预注册情感极化指数平均降低了0.03个标准差（p < 0.05），包括在100分的党派内与党派外情感温度计差异上减少了1.5度。我们观察到Facebook的活跃使用时间减少了0.37分钟/天，Reddit减少了0.2分钟/天，但X/Twitter增加了0.32分钟/天（p < 0.01）。用户报告的负面社交媒体体验有所增加，但在幸福感、新闻知识、外群体共情、对党派暴力的认知与支持方面未发现显著影响。这表明，桥梁性内容可以在不必然与社交媒体以参与度驱动的商业模式冲突的情况下，改善某些社会结果。