Exponential growth may look like a very slow increase at first, but it's still exponential growth.
Sigmoids may look like exponential growth at first, until they saturate. Early growth alone cannot distinguish between them.
If it's exponential growth. It may just as well be some slow growth and continue to be so.
On the other hand: Perception of change might not be linear but logarithmic.
(= it might take an order of magnitude of improvements to be perceived as a substantial upgrade)
So the perceived rate of change might be linear.
It's definitely true for some things such as wealth:
- $2000 is a lot of you have $1000.
- It's a substantial improvement of you have $10000.
- It's not a lot you have $1m
- It does not matter if you have $1b