Consciousness Blog 06 December 2010
New research from Georgia State University shows that open-mouthed, 'voiced' laughter is perceived as more positive than laughter produced with a closed mouth. Professor Michael J. Owren, an experimental psychologist at the University has reported a study in which listeners were presented with a series of laughter bouts in random order over headphones, including both open-mouthed and closed-mouth types, and asked to rate how positively they experienced the laughter.
All the laughter was rated positively, but open-mouth laughter was rated significantly more positively than closed-mouth laughter. Says Professor Owren: "One likely interpretation is that acoustic differences in positively toned laughter are correlated with changes in vocalizer arousal level. In other words, voiced, open-mouth laughter may in particular stand out because as laugher arousal goes up, the vocal folds are increasingly set in motion and the mouth opens during sound production. Listeners may or may not understand that connection at a conscious level, but may respond emotionally to these changes through unconscious processing." The experiment also confirmed earlier results in which female laughter was rated more positively than male laughter.
Owren says that 'unvoiced' laughter, which is routinely produced by laughers alongside 'voiced' laughter, has little emotional impact by comparison, something for which he does not yet offer an explanation. He is however clear about the social origins and functions of laughter:
think of laughter sounds as a kind of fundamental mechanism for building
up and maintaining positive social relationships. Laughter is almost a
dominant feature in social interactions. It clearly has some role in promoting
positive emotional bonds. But it's not clear how that's working."
Says Owren: "Human laughter resembles these primate calls in being strongly biologically grounded. The earliest - and we think still most prevalent use of these non-linguistic vocalizations - is to induce an emotional response in your listener."
"The interpretation that I’ve made about human laughter is that in human evolution, laughter changed, because by making it more voiced - ha-ha-ha - it became a more individually distinctive sound, and became a vehicle of mutual positive associative learning in individuals who genuinely liked each other."
"Human evolution, in particular put a premium on cooperative behavior among unrelated individuals. Laughter is actually a mechanism of fostering and maintaining positive relationships among individuals. So, there the argument is that the reason we laugh when we’re nervous or embarrassed or facing a social challenge, is that in the face of that social challenge you can essentially recruit your friend by inducing a little positive response in that individual toward you, to help promote common action."
Laughter presumably evolved as part of the 'social calculus' alongside empathy and intentionality (theory of mind), something that happened or at least began to happen among primates as their group living became more sophisticated. On this basis, one would not expect to find laughter among types of animal that have not developed empathy. There is no point in making a display that cannot be recognized by your conspecifics.
Not much research has been devoted to looking for laughter in other types of animal, although laughter-like behaviour has been described in rats and dogs, both being social species. It is tempting to suppose therefore that rats and dogs have a degree of intentionality. One might then expect to find both laughter and intentionality in other species with equivalent degrees of social sophistication such as squirrels and corvids.
Read more in Chapter Three of Agent Human by Michael Bell, The Evolution of Social Consciousness in Humans.