Temporal influence over the Last.fm social network

TL;DR

This study demonstrates that temporal influence from friends on Last.fm significantly affects users' listening behavior, distinguishing it from mere homophily or shared environment effects.

Contribution

It introduces a method to separate social influence from taste similarity and improves recommendation algorithms by incorporating temporal influence data.

Findings

Strong increase in listening to new artists after a friend listens to them

Temporal influence improves collaborative filtering and trend-based recommendations

Influence effects are measurable within hours of a friend's activity

Abstract

Several recent results show the influence of social contacts to spread certain properties over the network, but others question the methodology of these experiments by proposing that the measured effects may be due to homophily or a shared environment. In this paper we justify the existence of the social influence by considering the temporal behavior of Last.fm users. In order to clearly distinguish between friends sharing the same interest, especially since Last.fm recommends friends based on similarity of taste, we separated the timeless effect of similar taste from the temporal impulses of immediately listening to the same artist after a friend. We measured strong increase of listening to a completely new artist in a few hours period after a friend compared to non-friends representing a simple trend or external influence. In our experiment to eliminate network independent elements of taste, we improved collaborative filtering and trend based methods by blending with simple time aware recommendations based on the influence of friends. Our experiments are carried over the two-year "scrobble" history of 70,000 Last.fm users.