Playing a person a recording of their voice after changing the emotional tone can alter how they feel, scientists have found. The French researchers behind the digital platform which tweaks the tone of a person’s voice set out to investigate whether people are aware of the emotions their speech conveys.

The research builds on previous studies which have shown that people often attempt to hide their true emotions while speaking. Participants of the study read a short story aloud as their voice was played back to them. They were not aware that researchers were altering the emotional tone to make them sound happier, sadder or more fearful. When the researchers manipulated the tone of a participant’s voice, their emotional state changed accordingly.

“The relationship between the expression and experience of emotions has been a long-standing topic of disagreement in the field of psychology”, said Petter Johansson, one of the authors from Lund University, Sweden. Katsumi Watanabe, a psychologist at the Waseda University and the University of Tokyo in Japan and co-author of the study said the technique could be used as part of therapy, including for people with mood disorders.