Weber-Fechner law of stimulus for change

A small additional light is easy to notice in a dark room, but you need a much bigger increase to notice the same “difference” in bright light. Similarly, a small improvement in mood is easy to notice in someone with depression, but a much larger increase is needed to notice the same difference in someone without a mental disorder affecting mood.

According to the Weber–Fechner law, we notice changes in proportion to what’s already there, rather than as absolutes.

This applies to internal and external changes. The context of the change has greater relevance than the degree of the change itself in absolute terms. Small changes stand out when the baseline is small, and you need bigger changes when the baseline is big.

At the personal level, this law helps inform which practices you do and at what level of intensity, allowing saturation and establishing lasting change in the system.