Now there is a study in the Australian Journal for Grape and Wine Research that suggests hotness increases with increasing alcohol. In communication with the author it appears very experienced tasters were utilized and that the increase in hotness with alcohol was a real effect even with only 2% increases in alcohol. But what is hotness? It’s often described as a tactile sensation (like astringency) but in light of the surrounding evidence can we attribute hotness solely to alcohol? Probably not. Could hotness and bitterness be attributes that you see increase and decrease in concert when they are studied because they may be difficult to distinguish? The article did not look at the impact on bitterness as an attribute by itself though Dr. Richard Gawel did feel confident that the expert tasters could distinguish hotness and bitterness. So while hotness may indeed be an indicator of higher alcohol, we must remember that there are many 15 and 16% Alc. wines that are not hot. So it isn't solely alcohol. In fact it would be interesting to see if the hot sensation would be created in lower alcohol wines by removing a balancing.
Compound that may act with alcohol to prevent the hot perception?
I’ve determined to say at the beginning of every paragraph that alcohol matters! However, the more I look into the impact of high alcohol the less I am able to contend that its perceptible to most of us even at levels we all would determine as high alcohol (> 14.8%??). I recently returned from the American Society for Enology and Viticulture yearly conference where two more studies corroborated the notion that perceiving differences in the same wine that is alcohol adjusted is difficult. In fact Pickering et. al. showed that it is even difficult to link ethanol alone to things such as viscosity and density as some have suggested. So while it does seem to have a small influence on these attributes, it can hardly be isolated as the only factor. I think this study suggesting alcohol does have a small role in viscosity and density supports the idea that ethanol cannot be the only factor because the samples with the highest viscosity ratings were the mid-range levels (10-12 %) and the 7% and 14% were not different from each other. One last important note is that the viscosity study used nose clips, removing the possible clue that aroma (perhaps we can say style) may have on your determination of alcohol.