Campbell's Law
The more important a metric is in social decision making, the more likely it is to be manipulated.
Optimisation
People tend to optimize their behavior to improve a metric when it's used to determine success or failure, sometimes leading to ridiculous or dangerous results that impact the overall user experience. It's critical that we use data as a tool to assist in decision making instead of allowing metrics alone to determine a decision.
Limitation
Metrics cannot fully and accurately describe the world. Every metric collected reflects a decision about what is considered important.
Combination
The combination of quantitative metrics with qualitative data enables us to better understand the consequences of design decisions. Without this combination, consequences may be missed by relying on passively collected analytics data.
When to Use
Use metrics thoughtfully
When measuring user experience, be aware that metrics can influence behavior and may not capture the full picture.
Combine quantitative and qualitative data
Don't rely solely on metrics; also gather qualitative feedback to understand the full user experience.
Review metrics regularly
Regularly evaluate whether your metrics are still measuring what you intend and adjust as needed.
When to Avoid
Don't optimize for metrics alone
Avoid creating systems that optimize for metrics at the expense of actual user value or experience quality.
Origin
Campbell's law is an adage developed by Donald T. Campbell, a psychologist and social scientist who often wrote about research methodology. It states: the more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.