Adolescent non-users of e-cigarettes and cannabis (N = 1,462) participated in the in-class survey-based experiment. They were randomly shown 3 pairs of images featuring influencers promoting e-cigarettes alongside cannabis, (experimental group), or no-substance use or display (placebo treatment), or e-cigarette promotion alone (control). After viewing each pair of images, participants rated perceptions of influencer credibility (i.e., honesty, trustworthiness, knowledge) on the scale of 0 (e.g., dishonest) to 100 (honest).

Susceptibility to use e-cigarettes was assessed after participants viewed all the images. These outcomes were then compared among participants who perceived influencers as credible and those who perceived influencers as non-credible.

Adolescents (13-17 years of age) living in California were recruited by Tobacco Center of Regulatory Science at the University of Southern California (USC TCORS) to participate in the ADVANCE survey cohort focused on tobacco-related attitudes and behaviors. Participants completed the experiment, which was part of the survey at cohort's Wave 7, on Chromebooks in classroom. All participants provided informed consent and parental assent prior to participating in the experiment. The study was approved by the University of Southern California Institutional Review Board (HS-19-00682-AM016). Respondents were randomly shown 3 pairs of images featuring influencers promoting e-cigarettes (image 1) paired with cannabis (image 2), (experimental group), or no-substance use or display (two images featuring neutral profiles of influencers), (placebo treatment), or e-cigarette promotion (image 1) paired with a neutral profile (with no e-cigarette) of the influencer featured in image 1 (control).

Inclusion Criteria:

• English fluency,
• Current California resident.

Exclusion Criteria:

Not meeting these criteria:

• English fluency,
• Current California resident.