One Huge Psychological Effect To Use In Your Designs

The Familiarity Bias States that people already prefer what is familiar to them.

This has been proven in multiple different studies showing that humans prefer things that they already have used or are familiar with

This Psychological Effect states that users spend most of their time on other people's websites and apps so one way to utilize this psychological effect in your designs is don't stray too far from what people have done. Be innovated but consistent