Diffusion of responsibility
The weakening of each person's sense of duty to act when responsibility is shared across a large group.
Example
In a large office, staff can assume the facilities team will switch off idle equipment overnight.
The catch
The effect describes a tendency in groups and does not predict how any one person will behave.
In more depth
Diffusion of responsibility, explained.
Diffusion of responsibility is the logic behind 'my share is too small to matter', and it operates at several scales. Individuals use it about their own emissions, and countries use it when they point out that their slice of the global total is modest. Yet countries that each emit a small share together account for a large part of the world's emissions.
It differs from the free-rider problem, which involves a calculated wish to let others pay. Diffusion is quieter and often unintended, a fading sense that the task is yours at all. Organisations counter it by naming one accountable owner for each target and publishing progress against it, the same remedy that weakens the bystander effect in emergencies.