Influencers on Instagram: The Influence of Disclosure, Followers and Authority Heuristic on Source Credibility

Social media has become an important instrument for marketers to include in their marketing arsenal. A social network site that is of specific importance to many global marketers, especially those targeting the millennial generation, is Instagram. A popular marketing strategy used on Instagram is that of influential marketing where brands use influencers to promote their products and brands. Despite the popularity of influential marketing, little research is available on the use of influential marketing in an Instagram context. This study was therefore conceptualised and executed to investigate the influence of selected system-generated cues and user-generated content on the perceived credibility of an influencer as brand endorser and thus source to consumers on Instagram. Both qualitative and quantitative research were conducted. In the qualitative phase, two focus group discussions confirmed the variables that were measured in quantitative research which consisted of a 2 × 2 × 2 between-subjects factorial experiment. A non-probability convenience sampling technique realised a sample of 311 millennial female respondents (18–25) across 8 experimental groups. The results indicated that advertising disclosure significantly influenced overall perceived source (influencer) credibility, trustworthiness and homophily, while non-disclosure was perceived more positively by respondents than advertising disclosure. The findings of the study make a valuable contribution to a field in marketing that is growing in popularity and it is believed that insights gained can be used rewardingly by academic scholars and strategic marketers who have an interest in using Instagram as a marketing tool.