  Guided by the Persuasion Knowledge Model and the Attribution Theory, this
study investigates the perceived source expertise-product attribute congruence
and sponsorship disclosure as pertinent factors affecting the communicative
effectiveness of influencers. Instagram, with an immense influencer market
value projected at USD2.3 billion in 2020, was chosen as the platform context.
The study utilised a 2 (source expertise) x2 (product category) x2 (sponsorship
disclosure) experiment to examine the roles of source-product congruence and
sponsorship disclosure in affecting consumers' perception of extrinsic and
intrinsic source motives, consumer resistance and ultimately, advertising
effectiveness. Results revealed that the presence of a sponsorship disclosure
generated stronger perceptions of extrinsic source motives but did not impact
consumer resistance and advertising effectiveness, indicating that the
activation of consumers' conceptual persuasion knowledge may not necessarily
affect attitudinal persuasion knowledge. Source-product congruence, on the
other hand, had main impacts on intrinsic motives, consumer resistance and ad
effectiveness. In addition, hierarchical multiple regressions found that
source-product congruence triggers a multi-stage process where consumers'
perception of intrinsic source motives mediates consumer resistance which
subsequently, mediates the relationship between source-product congruence and
ad effectiveness.
