July 25, 2015

July 25, 2015

Written by Maximus Peperkamp, M.S. Verbal Engineer

Dear Reader, 

The following writing is my fourth response to the paper “Two Organizing Principles of Vocal Production: Implications for Nonhuman and Human Primates” by Owren, Amoss & Rendall (2010). 

"Pygmy marmoset (Cebuella pygmaea) vocal development is similar to that of humans in also showing a stage of babbling-like vocal behavior. In this species, calling typically begins in the first week of life, with infants producing spontaneous on-going streams of vocalizations that routinely juxtapose sounds that do not typically co-occur later in life.” 

Like humans, pygmy marmosets become more autonomous over the course of development and this changes the way in which they sound. Their loud and needy “shrieks, screams and squeaks”, gradually decreases as they become socialized to produce more “sonants and gruffs.” In humans, this change of sound is usually accompanied by the learning of language. 

Decrease of aversive sounding vocalizations in humans happens only to the extent that one has become a successful member of one’s verbal community. “As in humans, the marmosets make these sounds in the absence of obvious triggering stimuli. Unlike human infants, however, the monkeys produce recognizable versions of adult calls from the very beginning, with no evidence that auditory experience or motor practices are needed."

"Furthermore, although human babbling begins simply and becomes more complex, marmosets show the opposite trend. These animals begin with greater complexity (streams of species-typical and other sounds), then simplify and individuate the various calls later.” In humans an increase of complexity as a fine-tuning of vocal verbal behavior occurs.  

This research made the authors conclude that “some biologically grounded motivational process is involved and that the sounds provide important self-stimulating effects of some kind.” Human vocal verbal behavior is also grounded in “some biologically grounded motivational process” because our own voice provides “important self-stimulating effects of some kind.” However, this effect is only believed to occur in SVB, not in NVB. It cannot occur in NVB as the voice of the sender has not only a negative influence on the other person as the receiver, but in NVB the speaker is unknowingly and negatively effecting him or herself.

Neural evidence on primate vocalizations tells us what must also be true for humans: “The major finding is that subcortical, limbic-system structures are central in vocal production not only in monkeys and apes, but also across mammals in general.” There is “a virtual consensus among neuroscientists there are clear parallels between species-typical primate calling and human emotional vocalizations, such as spontaneous laughter and crying”, because humans have the same “affectively driven and limbically centered control system found in primates.” 

However, the picture is quite different for volitional control of human vocalization. The reader is reminded that only SVB is under volitional control. “Although speech production does show important subcortical involvement and affective influences, central aspects, such as motor planning and execution, are unambiguously cortical functions." This “subcortical involvement” either involves positive or negative affective influences.  In NVB there are negative affective influences, but in SVB there are positive affective influences. NVB is therefore a form of  coercive control, while SVB is always based on positive reinforcement.

Only as long as we keep fixating on the fact that we are different from primates, because we have language, is it “difficult to make substantive connections between vocal ontogeny in primates and spoken language development in humans.” If we pay attention to the fact that humans, like primates, produce sounds while they speak, we will be able to make these “connections.” Because of our language we are again and again inclined to keep focusing on how we are different from primates. 

The SVB/NVB distinction explains why “the unimportance of experience

is specific to the sound production component” of primate vocal behavior. Primates cannot, like humans, describe the sound of others and also cannot  describe their own sound to themselves. In other words, primates experience without having a verbal description of their own experience. However, this doesn’t mean their production of sound is not experienced. It simply means that it is not experienced as we humans do: by being verbal about it. 

“Not surprisingly, although acoustics, usage, and responding are all highly modifiable in human speech, characteristics of spontaneous, affect-triggered human vocalizations closely parallel those of primate calls in this regard as well.” Owren and Rendall are on the right track to acknowledge SVB and NVB in humans, a distinction that is based on how we sound while we speak. They differentiate between “affect-triggered primate and human vocalizations on the one hand and spoken language in humans alone on the other”, which, “indicate that fundamentally different systems are involved.”