Tom Kehoe, president of Yards Brewing, has seen such as shift firsthand.
"When we first brewed our Extra Special Ale, people would tell us it was way hoppy," Kehoe said. "Now people tell us they can't taste the hops at all."
The brewery has repeatedly tweaked its India Pale Ale to boost its hops character. What began as a malt-forward English-style IPA has evolved into a hops-dominated West Coast IPA.
Yards isn't the only one. Remember when Victory HopDevil IPA was as hoppy as it gets? These days hopheads shrug at it and reach for Hop Wallop imperial IPA instead. And how about Sierra Nevada Pale Ale? It's kids' stuff today, compared to the California brewery's Torpedo Extra IPA.
As scientists continually develop more potent varieties, and as brewers tinker with methods to draw even more aroma, flavor and bitterness from the plant, it's worth examining:
Are beer drinkers building up resistance to hops?
If we were talking about recreational drugs, addiction specialists would say the resistance is a result of neuroplasticity. That's what happens when the brain's synapses - upon repeated exposure to drugs - physically change. Euphoria wanes as the brain begins reacting not to the drug's physical effects, but to the act of procuring and ingesting the drug.
Could there be a similar hops addiction, one in which tracking down the latest, hoppiest ale is more important than the actual flavor of the beer?
I ran the theory past Gene Muller, president of Flying Fish Brewing, and he said that might explain why he often hears beer drinkers claim they won't drink anything weaker than a double IPA.
"You wonder how much of that is actual perception of hops," Muller said. "Or are they just drinking the label?"
While the passion for hops hasn't forced Flying Fish to change its recipes, Muller said it did recently lead the company to cease bottling its balanced ESB in favor of the newer, hop-dominant Red Fish red ale and Exit 16 double IPA.
Author Stan Hieronymus tackles the Lupulin Threshold Shift in his new, comprehensive paperback, For the Love of Hops: The Practical Guide to Aroma, Bitterness and the Culture of Hops (Brewers Publications).
While noting that some experts reject the phenomenon, Hieronymus writes that hop addicts may undergo what is known in human olfactory psychophysics (the study of odor) as "adaption." The more the brain becomes accustomed to hoppy aromas, the more it "expects a more-bitter drinking sensation."
Thus, brewers make a great effort to engineer the distinctive aroma of their beer. They select a highly aromatic variety - for example, grapelike Nelson Sauvin or piney Simcoe - to change the entire character of a simple pale ale. Or they boil in some rye grain to enhance the spiciness of, say, Cluster hops.
And they dry-hop out the wazoo.
That's technical jargon for adding hops after the beer is boiled. That way, the aroma doesn't escape a cloud of steam; instead, it's retained even after the beer is kegged or bottled.
Yeah, I know what you're thinking: If hops are like recreational drugs, then brewers are street-corner dealers, pushing, pushing, pushing you to next bitter buzz.
Get a grip, dude. Those hops are making you paranoid.
"Joe Sixpack" is by Don Russell, director of Philly Beer Week. For more on the beer scene, sign up for his weekly email at joesixpack.net. Email: email@example.com.