The Control Task was implemented to ensure the specificity of the psychological stress effects had on study outcomes. Therefore, the Control Task had a similar procedure and the same duration of the TSST, lacking except for only the psychologically stressful component. The control task consisted of (a) Participants had a 5-min a preparation section and anticipation phase (5 min ), (b) a reading task where they had to. Then, all participants had to be read a simple text in a low voice (5 min), and (c) an arithmetic section where they were asked to perform an easy mathematical calculation (5 mins).

The Trier Social Stress Task (TSST) is a standardized, 15-minute laboratory task designed to induce psychological stress in laboratory settings (Kirschbaum, Pirke, & Hellhammer, 1993). The TSST consists of three continuously successive phases: (a) an anticipation period (5 min); (b) a free speech task (5 min); and (c) a mental arithmetic task (5 min). As is standard in the TSST procedure, participants were told by a research staff member that they would provide a brief speech about "their dream job" in front of a critical audience. At the end of the speech, a member of the audience instructed the participant to conduct serial subtractions as accurately and quickly as possible.

Same as Arm

Time to vaping during the vaping delay task. Range of time delay is 0 minutes to 50 minutes.

Number of e-cigarette uses purchased during the self-administration phase of the vaping delay task. Range of puffs is 0 to 20.

Craving was measured using a visual analogue scale (VAS) asking "How much do you crave an e-cigarette right now?" with possible responses ranging from 0 (not at all) to 100 (extremely).