According to a new study published in the journal PLOS ONE, people change the pitch of their voice depending upon how dominant they feel with respect to the person with whom they are speaking.
The information for the study was gathered by simulating a job interview, where the discovery was made that people change their vocal characteristics, most notably pitch, to match the social status of the listener. What was found was that when someone felt that the person with whom they were speaking was dominant to them, i.e. a boss or potential boss, they raised the pitch of their voice to show they were submissive and not a threat.
"These changes in our speech may be conscious or unconscious but voice characteristics appear to be an important way to communicate social status. We found both men and women alter their pitch in response to people they think are dominant and prestigious," Dr. Viktoria Mileva, one of the researchers, said.
It should also be noted that people who feel naturally dominant tended to change both pitch and volume the least frequently.
All of this is to say, if you find yourself going into a higher register when speaking with your boss or superior, now you know why. It's not you, it's human nature.