Do We Need to Hear Others' Sounds to
Produce Emotional Vocalizations that Listeners Can Understand?
Disa Sauter - disa.sauter@mpi.nl
Max Planck Institute for Psycholinguistics
PO Box 310, 6500 AH Nijmegen
The Netherlands
http://www.mpi.nl/people/sauter-disa
Onno Crasborn
Radboud University
PO Box 9103, 6500 HD Nijmegen
The Netherlands
Daniel Haun
Max Planck Institute for Evolutionary Anthropology
Deutscher Platz
6, 04103 Leipzig
Germany
Popular version of poster
5aSC12
Presented on Friday morning, November 19, 2010
2nd Pan-American/Iberian Meeting on Acoustics, Cancun, Mexico
Humans use many types of signals to communicate to others how they feel. Emotions change how we gesture, the expressions on our face, and the sound of our voice. Are these changes in our behavior learned or do we have innate knowledge about how to produce them? Would we laugh the same way if someone tickled us regardless of whether we had ever heard anyone else laugh? In this research project we look at the role of auditory learning for developing non-verbal vocalizations like sighs, laughter, screams, and crying. To study this question, we examine the vocalizations produced by people born deaf. If the emotional sounds that deaf people make are similar to those made by hearing people this would mean that these kinds of vocalisations develop without the need to hear the sounds made by other people. On the other hand, if deaf people's vocalizations are different and cannot be understood by hearing people, then this would show that these kinds of sounds are learned from hearing.
In this study, we made recordings of emotional vocalizations from individuals who were born deaf and from hearing people. Each individual was asked what kind of sound would they would make if they felt in different ways, for example, what kind of sound they would make if they thought something was really funny, or if they felt very angry. They were asked not to speak, but to only produce non-verbal sounds, like laughter, sighs, and screams. We recorded vocalizations for negative feelings like sadness, disgust, and fear, and for positive emotions like amusement, relief, and triumph.
Can the emotional meaning of the sounds made by deaf people be understood by hearing people? This would mean that it is not necessary to hear other people's sounds for these vocalizations to develop. To test this question, we asked a new group of hearing people to classify the emotions felt in the vocalizations, using the sounds made by both deaf and hearing individuals. The results show that auditory learning is more important for some kinds of sounds than others. For example, the deaf individuals produced laughter expressing amusement and sighs when they felt relief, and these sounds were very well recognized by the listeners. This shows that emotional vocalizations of these feelings do not need auditory learning to develop. However, for most of the emotions, listeners found it more difficult to understand the emotional meaning of the sounds produced by deaf people. The listeners were better than guessing when trying to understand the meaning of the deaf people's sounds, but they found it harder than interpreting the hearing people's vocalizations. This means that for many kinds of emotional sounds, hearing the sounds of others is an important part of development for our own sounds to be understandable to others.
We also looked at how different the sounds made by the deaf individuals were from those of the hearing people, by measuring different kinds of acoustic information in the sounds. These included information like whether the sounds contained several bursts of sound or just one, information about how high the pitch was and how much it varied, and measures of the timbre of the sounds. We found that the sounds made by the deaf and hearing people were different on some of these measures, and that these differences were related to how easy the listeners found it to understand the emotions of the sounds.
This study shows that part of what makes our emotional vocalizations understandable to others is the fact that we learn from hearing the sounds that others make. However, this auditory learning is more important for the sounds of some emotions than others, and also seems to be more important for some aspects of how the sounds are made than others. We are now looking at whether the way the face looks when we vocalize can tell the viewer how the sound is made, and we are especially interested in whether deaf and hearing individuals are differently sensitive to this information.