interaction design - How does something become "common knowledge"?

There was a time when there were no smartphones and computers.

Now terms like "Tap", "Swipe" or "Double-click" are common for most people in the world.

How do some interactions turn into common knowledge?

For example, even with rules of the road. There are learned rules and there are unspoken rules like this one: Someone flashes their lights at you because your high beams are on. You just know.

There are lots of times when I'm designing something and I try to lean towards established norms because I assume that's usually the path of least resistance. But how do these things get established to begin with?

More specifically: What is the process to reduce learning curve and create convention?

Note: i've read this other post ( Is it ever acceptable to break extremely common interaction functions? ) but it doesn't answer the question of how these commonly accepted interactions become convention in the first place.

Answer

You are blending two distinct concepts here: The development of ideas and the propagation of ideas.

The examples you have listed were all developed through a great deal of user research over many decades of interaction design. "Swipe" and "double click" did not emerge out of the ether, they were developed by industry leaders through an iterative process of observing and developing. This is the scientific research field of human-computer interaction, and there are a huge number of research papers on the physiological, psychological, technological and sociological drivers for interface design.

Those ideas were then propagated through widespread dissemination and imitation of both the the final products and the supporting research literature. This process is the research field of socio-cultural evolution and memetics. There are a similarly large number of papers on the driving factors behind technological adoption patterns.

The interaction of these two concepts is what you are describing as "becoming common knowledge". Hopefully I have given you enough to continue your own research.