UCL Changing Minds

In a classic paper, psychologist Ziva Kunda (1990) explained why. We don’t reason with one goal. We juggle two.

You’ve seen it: Strong evidence. Clear logic. Zero movement. This isn’t stupidity or bad faith. It’s psychology.

Why do facts so rarely change minds? Because most debates aren’t really about truth 🧠

Why forecasts feel convincing at work 👇 They’re vivid, detailed, and coherent — not necessarily accurate. Fluency ≠ truth.

This explains the planning fallacy: We underestimate how long tasks will take — even when we’ve been wrong many times before. Experience alone doesn’t fix it.

Why do projects always take longer than we expect? It’s not just optimism. It’s how the human mind simulates the future 🧠

7/ This helps explain classic findings like the bat-and-ball problem. People give the “wrong” answer not because they’re incapable, but because deeper reasoning often isn’t worth the effort.

6/ In particular, when: • The stakes are low • The cost of thinking harder outweighs the benefit • Mental resources are better spent elsewhere Accuracy isn’t free.

1/ When is it rational to be inaccurate? 🧠 Sounds wrong at first. But it’s one of the most important ideas in behavioural science. 🧵⬇️

8/ 🚀 Why this matters for organisations If you expect perfect optimisation, real behaviour looks irrational. If you consider time pressure, incentives, and cognitive load, behaviour often makes sense.

7/ They’re sensible trade-offs. What looks irrational under perfect optimisation often looks smart once constraints are taken seriously.

1/ Not all rationality is the same 🧠 When people talk about decision-making, they often assume there’s one gold standard of being “rational”. There isn’t. 🧵⬇️