Yes, it seems equally likely that it would make things worse. But it seems unlikely that it would have no effect. It is unlikely that these are the optimal shap

Yes, it seems equally likely that it would make things worse. But it seems unlikely that it would have no effect. It is unlikely that these are the optimal shapes of the up and down buttons. For what it's worth, I think the Google way to solve this would be to figure out which metrics you can associate with quality and A/B test the impact of the UI changes. Setting up an A/B framework might be more work than you want to put in. But there might be a UI that encourages higher quality that you could discover empirically.