The original argument I read was that slowdowns or waits past a certain time affect mental flow. The flow is basically you being in the zone coding optimally. I

The original argument I read was that slowdowns or waits past a certain time affect mental flow. The flow is basically you being in the zone coding optimally. Interruptions like phones can jolt a person out of flow. So can long wait times. If person is in flow, you want them cranking out as much output as they can with no slowdowns. That was an advantage of Smalltalk and LISP. Any language with REPL or IDE supporting something like it will let one do this.