As the Covid pandemic has worn on and virtual platforms played an ever-increasing role in our personal and professional lives, Zoom fatigue became a growing concern.  A study from the University of Michigan suggests that one reason why Zoom calls can be so draining is that we struggle to catch the various subtle cues that occur during the course of a conversation.

The researchers highlight that when we have conversations the transition time between speakers is usually around 200 milliseconds.  This means that the listener has to simultaneously absorb what the other person is saying and plan their response.  Our brains try and help us with this by synching the syllable rate of us and our colleague to assist us with timing.  It transpires that video platforms mess up with this process.

“Oscillators can tolerate a certain amount of deviation (in syllable rate), without desyncing, which is necessary to handle the fuzzy rhythms of speech,” said Boland, the study’s lead author. “However, the variable electronic transmission delays in videoconferencing are probably sufficient to destabilize these oscillators.”

Out of synch

The study found that when we converse on Zoom, we tend to take longer between turn initiations, which is sufficient to destabilize our brain, which in turn contributes to the mental fatigue caused by Zoom calls.

Zoom says that the transmission lags on their service are below 150 milliseconds, or less than 1/5th of a second.  They believe this provides a level of service without any noticeable lag.  The research shows, however, that lags of between 30 and 70 milliseconds can have an impact.  30 milliseconds was chosen as the fastest realistic lag achievable by internet traffic.

“Short lags cause problems because the period of a neural oscillator tracking speech rate would need to be in the range of 100-150 milliseconds,” the researchers say.

They explain that the human voice already stretches that tolerance for variability, so adding even a small transmission lag would run beyond the capacity of the oscillator.  This means that when we use Zoom, we need to use less automatic cognitive mechanisms, which in turn makes talking via video chat platforms awkward and less enjoyable.