There's another way to tell: Switch to organic for the "dirty dozen" fruits and veggies[1] for three weeks. Then try conventional again. In my own experience I couldn't tolerate conventional anymore, and the difference is more than placebic: Headaches and yuck feeling.
Also in my experience, organic tastes WAY better. For example I never liked the taste of conventional celery; some bitter aftertaste (pesticide residue?) and just bland. But organic celery really pops, with no aftertaste. Baby carrots are noticeably tastier as well. The difference is so stark I think I could validate these on a double-blind test any day.
I'm not saying my own personal testing has proven anything to you. I'm asking you to prove it for yourself. Try it and see. But you already are, so...
Anyway if double-blind is what you need to be convinced, then by all means do the same test double-blind.[1] Shouldn't be terribly difficult to craft such a test for yourself.
> In my own experience I couldn't tolerate conventional anymore, and the difference is more than placebic: Headaches and yuck feeling.
I think that would be the definition of a placebo effect. Headaches and yuck feeling when eating food you perceive as dirtier/less healthy.
Maybe you should get two of your friends together and do a double blind test. Have one of your friends go shopping, take the vegetables out of the bag, and write down which is which. Then have your other friend who doesn't know which is which give both portions to you and see if you can tell the difference. It would be interesting for sure.
> For example I never liked the taste of conventional celery; some bitter aftertaste (pesticide residue?) and just bland
Bitterness is normal in celery though the degree is manageable by techniques that are orthogonal to non-organic vs. organic status. To the extent that there is a non-placebo difference, it's probably that your conventional supplier is more devoted to rigorous labor cost cutting then your organic supplier, which is likely to become less and less common for randomly chosen organic vs. non-organic as organics become more and more mass market and less upper-middle-class niche.
the Dirty Dozen is a dramatic way of saying "don't eat the outer skin of foods that are not-organic". It backed by reasoning from simplistic assumptions (non-organic chemicals on skin == bad), not scientific tests.
When I eat Non organic beetroot, it just feels like I am eating some pesticides. Same with non-organic corn. Try keeping in this mind when you eat these vegetables next time and I am sure you will catch the aftertaste.
If they're thinking about pesticides and their taste while eating, it might be hard to seperate the thought from the reality. Like, thinking about maggots while eating your rice. I'm sure your rice doesn't contain maggots, but do you really feel like eating rice right now?
Try a double-blind test and ask a series of questions. Some of the questions about taste should be the things you're looking for. Others should be irrelevant, just to set a baseline. Perceptions of taste are very subjective and easily influenced. Experimental rigour is necessary to mitigate that.
The first time I really enjoyed celery was organic. (Same variety as conventional.) I was expecting the same nasty aftertaste and was pleasantly surprised.
Take that for what it's worth, but do suggest you give organic celery a try, see if you notice the same. Do it double-blinded if you must.