The Allen Curve describes the relationship between physical distance and communication by Thomas J Allen, an MIT professor in late 1970s. He found the as distance increases, our interactions decline exponentially and people collocated are more likely to speak to one another.

Employees who work in close proximity to each other are more likely to communicate with each other on a regular basis than those who work farther apart.

His findings suggest the 50 meters as a cutoff point. Any two people beyond that point were not communicating properly.