Functional magnetic resonance imaging (fMRI) will be used to measure blood oxygen-level dependent (BOLD) signal in response to tobacco vs. strawberry-vanilla ECIG flavors at baseline. The means reported are the average percentage of BOLD signal change between the fMRI task odor conditions (tobacco vs. strawberry) identified using a whole-brain one-sample t-test with FSL software. Positive values indicate stronger BOLD signal during tobacco odor cues and negative values indicate stronger BOLD signal during strawberry odor cues.

For this within-subjects comparison of laboratory task conditions, we included all 19 participants who completed a functional MRI scan at baseline. All assigned groups were combined since group assignment was not a variable of interest for this aim.

Functional magnetic resonance imaging (fMRI) will be used to measure changes in blood oxygen-level dependent (BOLD) signal for the tobacco>strawberry contrast across 18 mg/ml vs. 0 mg/ml nicotine concentration groups from baseline to 4-weeks post-randomization using a whole-brain repeated measures ANOVA with FSL software. The means reported are the difference (4-week post-intervention - baseline) of the average percentage of BOLD signal change between the fMRI task odor conditions (tobacco vs. strawberry). Positive values indicate increases in tobacco>strawberry BOLD signal and negative values indicate decreases in tobacco> strawberry BOLD signal.

This analysis includes 15 participants who completed baseline and post-intervention functional MRI scans. Groups assigned to nicotine vs. no nicotine were compared and flavor sub-groups within the nicotine groups (tobacco vs. strawberry) were combined, since flavor was not a variable of interest for this aim.

Functional magnetic resonance imaging (fMRI) will be used to measure changes in blood oxygen-level dependent (BOLD) signal for the tobacco > strawberry contrast across flavor groups (tobacco vs. strawberry) from baseline to 4-weeks post-randomization. The means reported are the difference (4-week post-intervention - baseline) of the average percentage of BOLD signal change between the fMRI task odor condition (tobacco vs. strawberry) identified using a whole-brain repeated measures ANOVA with FSL software. Positive values indicate increases in tobacco>strawberry BOLD signal and negative values indicate decreases in tobacco> strawberry BOLD signal.

This analysis includes 15 participants who completed baseline and post-intervention functional MRI scans. Groups assigned to tobacco vs. strawberry were compared and nicotine sub-groups within the flavor groups (nicotine vs. no nicotine) were combined, since nicotine was not a variable of interest for this aim.

Changes in self-reported ECIG dependence will be measured using the Penn State Electronic Cigarette Dependence Index (PSECDI). Total scores on this 10-item measure range from 0 to 20, with higher scores indicating higher levels of e-cigarette dependence. The means reported here are the week 4 - week 2 difference scores of the total dependence score. Positive means indicate increases in e-cigarette dependence, while negative means indicated decreases in e-cigarette dependence.

This analysis included 14 participants who completed the 2-week check-in and 4-week post-intervention visits and completed the PSECDI.

Changes in subjective experiences of ECIG use related to liking and satisfaction will be collected via a self-report survey. The survey consists of 21-items (7-reversed scored) with response options on a 7-point likert scale and total scores ranging from 0 to 126. Higher scores indicate more ECIG liking and satisfaction. The means reported here are the difference of the total scores at week 4 - week 2, with positive means indicating increases in e-cigarette liking and negative means indicating decreases in liking. Note that standard deviation cannot be reported for groups with only one participant.

This analysis includes 8 participants who completed the e-cigarette evaluation scale at the 2-week check-in and 4-week post-intervention visit. Only participants who reported using the study e-cigarette since the last study visit completed the evaluation scale.

Changes in self-reported craving to smoke/vape were measured with 3 questions on amount, intensity, and self-control using visual analogue scales ranging from 0 to 10 prior to completing the functional MRI scan. Total scores range from 0 to 30 and higher scores indicate more craving. The means reported here are week 4 post-intervention - baseline difference scores of the total craving score. Positive means indicate increases in craving, while negative means indicate decreases in craving.

This analysis includes 15 participants that completed the craving scales before the functional MRI scans at baseline and at the post-intervention visits.