Thanks. I wasted a bunch of money on catnip when it turned out my cat was immune, which I didn't even know was a thing.

After reading up on it, it seemed like there were gaps in the research literature - most of it was hopelessly old and inaccessible, there was no single estimate for how frequently cats respond to catnip and substitutes (so I could meta-analyze/multilevel-model this easily), and no data on the relationships of responses within a cat (so if your cat is immune to catnip, what do you optimally try next?) but this is easy to experiment with since cats are common (I've already gotten set up with several cat toys impregnated with catnip/valerian/honeysuckle so I can test each cat I run into with a battery of stimulants).

So after jailbreaking all the relevant literature, maybe run an online survey of catowners, then combine everything to get the population frequency of catnip response, and then begin experimenting with available cats to get an idea of whether responses are correlated and how frequently cats respond to each stimulant. Then catowners will know the risk of catnip immunity and each stimulant they should try next. See http://www.gwern.net/catnip

A minor contribution, perhaps, but there are a lot of catowners out there and it would be nice to bring some clarity to this area.