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Have you heard about anchoring? It's a cognitive bias, a shortcut our brain uses. In software engineering it's seen when we unreasonably prefer the first proposal we hear over all later proposals. No matter how much better the later proposals are.

If I give you a task and also a solution that worked on a similar task in the past, you will try to bend that solution to also work on the new task. Even though research has experimentally shown we write fewer bugs if we start from scratch.

As developers we like to think of ourselves as highly mathematical beings, highly precise and logical.

But the human brain isn't really as logical as it has been painted out to be. The brain takes lots of shortcuts and it's not at all transparent about it.

This talk is exposing ways in which cognitive biases creep into our work, cause bugs and rollbacks, and how to fight back.

Devoxx

Cognitive biases are mental shortcuts that affect developers in ways they rarely notice. Anchoring bias causes developers to reuse old code or AI-generated solutions without deep analysis, leading to more bugs and dangerous overconfidence. Optimism bias makes developers drastically underestimate project complexity and duration — studies show developers estimated a 2,400-hour project at just 660 hours on average. Confirmation bias corrupts debugging, code reviews, and testing by causing developers to seek only evidence that confirms existing beliefs. Other biases covered include availability bias, bystander effect, sunk cost fallacy, hyperbolic discounting, and status quo bias. Research shows biased actions are reversed 80% of the time, wasting significant effort. The antidote is deliberate skepticism: questioning your motivations, slowing down rushed projects, and consciously testing for unexpected behavior rather than just happy paths.

Why smart developers write silly code by Ines Panker