  Algorithms that favor popular items are used to help us select among many
choices, from engaging articles on a social media news feed to songs and books
that others have purchased, and from top-raked search engine results to
highly-cited scientific papers. The goal of these algorithms is to identify
high-quality items such as reliable news, beautiful movies, prestigious
information sources, and important discoveries --- in short, high-quality
content should rank at the top. Prior work has shown that choosing what is
popular may amplify random fluctuations and ultimately lead to sub-optimal
rankings. Nonetheless, it is often assumed that recommending what is popular
will help high-quality content "bubble up" in practice. Here we identify the
conditions in which popularity may be a viable proxy for quality content by
studying a simple model of cultural market endowed with an intrinsic notion of
quality. A parameter representing the cognitive cost of exploration controls
the critical trade-off between quality and popularity. We find a regime of
intermediate exploration cost where an optimal balance exists, such that
choosing what is popular actually promotes high-quality items to the top.
Outside of these limits, however, popularity bias is more likely to hinder
quality. These findings clarify the effects of algorithmic popularity bias on
quality outcomes, and may inform the design of more principled mechanisms for
techno-social cultural markets.
