I’m pretty sure this idea isn’t new, but I can’t find another source talking about it directly. I think I got it from a Yudkowsky essay talking about venture investing.
There’s a strong analogy between the rate of a chemical reaction, and the rate at which new users adopt an app.
In chemistry, there’s a standard picture of the energy in a reaction:
Here’s the idea in english. Imagine the chemicals in the reaction as a bunch of balls sitting on the flat part of the curve pictured, right above “reactants”. The big hill, called the energy barrier, keeps them in place. If the big hill were removed, the balls would all roll down to the right, where it says “products”. In physical terms, when a ball crosses the hill and rolls down the other side, it represents a few reactant molecules turning into product molecules.
But the balls don’t just sit there. In real life, there’s heat! It’s like we’re shaking the balls around. Shake hard enough, and they’ll start to bounce up over the hill; the reactants will turn into products. The harder we shake (i.e. the more heat we add), the faster balls will bounce over the hill, and the faster the reactants will turn into products.
But shaking doesn’t just turn reactants into products. Shake enough and, every once in a while, a ball from the product side will bounce back to the reactant side. This is a reverse reaction - products turning back into reactants. If the reactants are much higher in energy than the products, then balls will bounce forward much more than backward. But if the two sides are about even - if reactants and products have about the same energy - then the balls will bounce backward just as often as forward.
Product and UI
We can use exactly the same model for user adoption of a product, e.g. an app.
Now, the balls represent potential users. People on the “reactants” side are not yet users; people on the “products” side have fully adopted the product. In between, there’s a hump - the energy barrier which a potential new user must cross.
Generally, we want to get everyone to adopt our product. In order to make that happen, we need two things.
First, we want to make the energy barrier as low as possible. In other words, make it easy for new users to adopt the product. Things like a steep learning curve or long onboarding flow or upfront cost make the energy barrier higher. A lot of UI design, especially for onboarding, is focused on making that barrier lower.
But the energy barrier is only half the equation. We also need the “products” to have much lower energy than the “reactants”. In other words, our users need to get lots of value out of the product once they’ve adopted it. If the users are about equally happy between using the product or not, or if they’re happier without the product, then they’ll just bounce back to the other side. We’ll see high “churn”, with lots of users leaving.
In chemistry, a strong reaction requires two pieces: low activation energy and a big energy drop. A successful product requires the same two pieces: low activation energy (easy acquisition/onboarding) a big energy drop (value for the user). If either one of those is missing, then the product will not see much use.