System 2 Is Too Expensive for Your Banking App
· 2 min readNobody uses System 2 to check their bank account.
I just finished Nicky Hayes's A Little History of Psychology. Near the end, she covers Daniel Kahneman and Amos Tversky's split between System 1 and System 2.
System 1 is automatic and fast. You walk down the street, someone asks you 5 + 2, and you say 7 without breaking stride.
System 2 is deliberate and slow. Someone asks you 27 × 17 and your feet actually stop moving on the pavement. Your brain has to shut down everything else to do the math. It burns real energy, so we avoid using it whenever we can.
The trap #
I work on mobile banking apps in France. We build them in System 2.
Product managers, engineers, and compliance people sit in quiet rooms with big monitors. We read every word on the screen. When a new fraud risk or regulation shows up, the default answer is to add a warning: a modal, three paragraphs of legal text, a checkbox, and a confirm button.
On paper, the user is warned. The bank is covered.
On the phone, the user is walking down the street. They see a wall of text blocking what they came to do, look for the blue button, and tap it in half a second.
Adding a warning doesn't wake up System 2. It trains System 1 to tap faster.
What to do instead #
If your safety model depends on a customer reading fine print on a six-inch screen, you don't have a safety model.
Do the work in the system. If an API can check that the beneficiary name matches the IBAN, check it in the background. Keep the normal flow clean so you don't train people to click through noise.
Save the interruption for when something is actually wrong. Not a generic lecture about scams, just the one fact that breaks the habit: this IBAN belongs to Company X, not the person you typed.
One screen, one question. Turn 27 × 17 back into 5 + 2.
Your users aren't going to stop walking on the sidewalk to use your app. Stop designing as if they will.