Microblogging platform Twitter uses an algorithm that amplifies the reach of politically right-leaning sources more than that of politically left-leaning sources, suggested a study. Twitter uses the algorithm to personalise the content its users see on their home timelines.

Cambridge University professor Ferenc Huszar and his colleagues quantified whether Twitter’s algorithm amplifies left-leaning or right-leaning content using a randomised control group of nearly two million daily active Twitter users chosen by the platform to receive content in reverse-chronological order without personalisation and a treatment group representing 4 per cent of all other accounts with personalised timelines.

The authors analysed the algorithmic amplification effect on tweets made by 3,634 elected politicians from major political parties in seven countries that are highly represented on Twitter.

The authors also measured the algorithmic amplification of 6.2 million political news articles shared in the United States. The results suggest that in six out of the seven countries, the personalisation algorithm significantly favoured the amplification of tweets from politically right-leaning sources.

Right-leaning US news services were also preferentially amplified. Contrary to popular assumptions, far-left-leaning and far-right-leaning outlets were not significantly amplified, compared with politically moderate outlets.

According to the authors, the results contribute to the evidence-based debate on the role of personalisation algorithms in shaping political content consumption.