Default Effect
We tend to follow the path of least resistance when making decisions.
The research
When it comes to donating organs, countries that we think of as very similar behave very differently. Few people donate organs in countries where you need to 'opt-in' by checking a box — UK (17%), Germany (12%), Denmark (4%). In countries where you need to actively 'opt-out' — France (99%), Austria (99%), Sweden (86%) — many more donate. Since people don't opt-out in these countries, they simply go with the flow and donate organs.
Johnson et al. (2003). Do defaults save lives?
Even a dead fish can go with the flow.
Thought starters
Make the preferred option the standard path to follow
Highlight the benefits people may miss out on if they select other options
Explain why many other people opt for this option in a similar situation
Try combining this with (O7) Social norms – descriptive norms.