Designing the Record Button

A few days earlier, Erik, one of my students at the 2nd year Chinese course at Columbia University, invited me to do an interview for his final class project. Before and after the interview, we had several comments about making sure the record button is pressed. This anecdote reminded me of an episode of The Big Bang Theory. I decided to mix our interview clips with The Big Bang Theory moments into this following short clip. 

 

Later, I decided to look into literature about designing a record button. I found a paper by McKnight and Read on using children's understanding of icons in designing an interface. 

Any insights?