Do callcenters even need to train their operators to get the ideal speaking rate?

I recently read an interesting article at nu.nl about the discovery that the speaking rate has a big influence on the degree of likelyhood that people will be convinced by the speaker. Apparently if someone speaks too fast, he or she comes across as untrustworthy. However, if someone speaks at a slower pace, he or she will seem more stupid toward listeners which will not be an advantage for convincing people.

For this reason a training for speaking at a rate of exactly 3,5 words a second plus regularly dropping short silences could be beneficial for companies that rely on convincing operating telephonists. Maybe training is not even necessary since it’s easy for people to imitate a way of speaking after hearing it for a while. That is why perhaps the operators should listen to a tape with a voice that speaks in the ideal pace every now and then during their work. In this way after a few phone conversations they can (again) be reminded to the ideal speaking rate and keep up talking like that.