Confirmation Bias and Shoes

I have been reading Thinking Fast and Slow which I would highly recommend. If you have read a summary and think you know what’s in the book you are wrong. I think it takes example after example to actually internalize how easily we are influenced by things we don’t notice. I am writing up some personal notes but they aren’t done. This is a placeholder using an experience I had today.

I need to replace my trail runners. I have very hard to fit feet. I had narrowed down the choices to Altra Superior 4.5 and Inov-8 G 270. I have been wearing Altras for several years, but they keep tweaking the shoe which means I never know if the next shoe I purchase from them will work as well as the previous. They also wear out more quickly than I would like.

I was excited by the Inov-8. First, Inov-8 don’t change shoe designs. I wore their Flyroc-310 for several years… the 14th pair was just like the first. Second, they were using space-age materials which was suppose to add durability and performance. I read that they were using an improved foam which has better energy returning properties. They had updated the design of the 260 G including a wider toebox, which seemed like it would fit my foot. The 260 G toebox was a bit too narrow for me. Seemed like a winner.

So… I took these shoes out for several runs. It seemed to me that the Inov-8 was was performing better than the Altras… they felt more energetic and had a better “ride”. Later I put one of each on a foot and walked around. Both feet were happy… nothing stood out, but when I was concentrating on the feel, I prefered the Inov-8.

Then I looked at metrics gathers from RunScribe sensors. The Altras were performing better. More efficient, lower shock and braking Gs, slightly better form. Hmm… later I put one of each on my feet and went for a run while listening to an engaging podcast. I set an alarm so that 3/4 of the way through the run I would pause to consider which foot felt better. When the alarm went off I had forgotten which foot had which shoe. My assessment… the right foot felt a tiny bit more comfortable. When I got home I looked down. The right foot was the Altra.

So it seems my expectation (and hope) that the Inov-8 was going to be superior made me look for confirmation this was true. Objective metrics suggested that the Altra were better. My attempt to do a pseudo blind test resulting in a slight preference over the Altras. Was this a new confirmation bias? I don’t trust myself to know.

What am I doing? The Altras are cheaper and Jackie prefers their color… so that’s what I am going to use for now. If I have trouble finding the Altra Superior 4.5 in the future, I know the Inov-8 270 G will be an acceptable alternative.

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