Over-confidence and Cola
Mark Honeychurch - 7th July 2025
The article from Aaron Davies about blind testing diet colas is a really interesting one for me. As a little background info for you, Aaron is an ex Jehovah’s Witness and was a NZ Skeptics committee member a few years ago. In the article I’m the “Mark” mentioned in the testing. So, if you’ve read the article already, you’ll know that when challenged with picking out my favoured beverage, Diet Coke, from a line-up of identical looking drinks in identical looking cups, I successfully identified the Diet Coke.
You might think that being able to differentiate Diet Coke from other sugar-free Coca Cola drinks, as well as other value colas, would be a vindication of my choice - that I know what I like, and that there’s no substitute for The Real Thing™. But no, this is not how my thought process went. Rather than being filled with the knowledge that I just knew the truth, I couldn’t stop thinking of the fact that I really wasn’t very sure about my selections. I had a vague feeling that the Diet Coke drink was actually Diet Coke, but there was nothing concrete about it… no “aha” moment when I put the cup to my lips. It kind of tasted a bit more like Diet Coke than the others, but not by much. I was fully ready to accept, when the results were revealed, that I may well have chosen the wrong cup, and that I might have to admit that my cherished Diet Coke tasted less like Diet Coke to me than The Warehouse’s Nice brand did.
My takeaway message from this experiment wasn’t that I was right, it was that I totally lacked the confidence that I was right. As a skeptic I’d walked into Aaron’s test already understanding intellectually that my default mental idea that there was no substitute for Diet Coke, because nothing else tasted the same and I’d made my choice for perfectly rational reasons, was probably wrong. And because of this I made it clear that there was a good chance I would not be able to pick the Diet Coke. But even knowing it academically didn’t prepare me for the depth of my uncertainty once I’d tasted all the drinks. I found myself somewhat humbled by my lack of confidence.
As an aside, when it comes to brand favourites there used to be a TV show in the UK called Eat Well for Less where families struggling to pay their bills were given a mix of their favourite expensive branded products and cheaper alternatives for a week, all blinded of course by being decanted into unlabelled containers. Unsurprisingly, many people on this show can’t tell the difference between their beloved brand and a supermarket’s own label - although a good many times, people can’t bring themselves to buy the cheaper versions because of the lure of branding. There’s also a version of the show that was made in New Zealand recently.
I guess, apart from anything else, this fun little experiment at the start of a night of drinking beer and playing video games really brought home to me the importance of blinding as a way of figuring out if something is true or not. In our everyday lives there is so much that we just assume to be true. Much of it we’ll be right about, but for some things we’ve likely ended up coming to a bad conclusion and are holding an incorrect belief. And especially when it comes to topics like medicine and health, these bad conclusions often lead people to recommend ineffective treatments to others.
The experiment reminded me of a couple of high profile dowsing tests that have been run by skeptics, where in each case the dowsers, or diviners, were able to repeatedly successfully detect water in a container when they could see where it was, but unable to reliably do the same once the location of the water was obscured: