According to the authors of Designing for Growth, what question encourages you to imagine all of the possibilities without regard to the reality of the ideas

i believe the answer is:   psychological  experiment

in this experiment, wilhelm wundt became the first person that implement scientific method in analyzing the pyschological phenomenon.

due to this result, wilhelm wundt also able to make psychology to be acknowledged as a separate scientific field from biology.

answer; no longer than a reasonable period of time;