All participants will be given all e-liquids (i.e. 3 flavor conditions all containing nicotine) in this within subject cross-over design study. Participants will be randomized in the order in which they receive the flavor conditions (across 3 visits).

All participants will be given all e-liquids (i.e. 3 flavor conditions all containing nicotine) in this within subject cross-over design study. Participants will be randomized in the order in which they receive the flavor conditions (across 3 visits).

All participants will be given all e-liquids (i.e. 3 flavor conditions all containing nicotine) in this within subject cross-over design study. Participants will be randomized in the order in which they receive the flavor conditions (across 3 visits).

E-liquid containing 36mg/ml pronated nicotine will be administered with sweet e-cigarette flavor.

Change in appeal at each flavor as measured by the computerized Labeled Hedonic Scale (LHS). Participants will self-report their responses using a computer mouse to indicate where on the scale response falls. The Labeled Hedonic Scale (LHS) is a bipolar category ratio scale that ranges from -100 (most disliked) to 100 (most liked), with 'neither liked nor disliked' as midpoint.

Change in sweetness, coolness, irritation, and bitterness at each flavor as measured by the computerized Generalized Labeled Magnitude Scale (gLMS). Participants will self-report their responses using a computer mouse to indicate where on the scale response falls. The Generalized Labeled Magnitude Scales (gLMS) are category ratio scales with seven semantic labels: "no sensation", "barely detectable", "weak", "moderate", "strong", "very strong", and "strongest imaginable", positioned quasi-logarithmically as per empirically determined semantic magnitudes on a 0-100 scale (strongest imaginable at the 100 end).

Change in reinforcing value at each flavor. Participants will use the multiple choice procedure to self-report their responses using a computer mouse to indicate where on the scale response falls. Following each puffing bout, participants will be asked to make discrete hypothetical choices between 10-puffs of the e-cig they had just used or a series of 44 monetary values ($0.25-$15.06). The minimum monetary value at which money is chosen over the e-cig puffs is a contingency-based estimate of e-cig value. At the end of each lab session, participants will be given a choice between another 10 e-cig puffs or one of the monetary amounts they picked in the Multiple Choice Procedures completed earlier.