Community samples have shown that up to a third of 8- and 9-year olds report sipping alcohol (Donovan and Molina, 2013; Jackson et al., 2013), demonstrating that very early substance experimentation begins in late childhood. Studies have found that early sipping predicted drinking onset (i.e., consuming full alcohol drinks) by age 14 (Donovan and Molina, 2011). Similarly, Jackson and colleagues (Jackson et al., 2015) found that sipping alcohol prior to 6th grade predicted drinking a full drink, getting drunk, and drinking heavily (i.e., 3 or more drink equivalents on an occasion) by 9th grade, even after controlling for a range of etiologically relevant environmental and individual difference covariates. In contrast to the literature on alcohol, which sometimes operationalizes determinants of a sip and having a full drink as distinct, the field of nicotine has not tended to make this distinction. With few exceptions (Okoli et al., 2008; Alexander et al., 1999), studies rarely distinguish between having had a puff and having had one or more cigarettes and data are generally missing on interim levels of progression from a puffs to
