Hemispheric lateralization of language

The most basic activity of this blog is to maintain vigilance of ongoing science, particularly in the fields of psychiatry and paleoanthropology but also in numerous other fields, and to apply all relevant new findings to the Blog’s broad paradigm of the human mind. In the September 2nd issue of Science an article entitled, “Neural mechanisms for lexical processing in dogs” by Andics, et al. appeared. If you have ever had to lie still for an MRI, you can appreciate how difficult it would be to train an animal to sit still enough to have an even longer-lasting functional MRI while keeping the animal alert enough to respond to human verbal testing routines. Primates certainly could not be trained to do so.

These researchers found that, similar to humans, dogs process the cognitive (left hemisphere) and emotional (right hemisphere) components of language separately in the same way that humans do. Anyone with a dog knows that, if you say, “Bad dog” with a loving voice, the dog will act positively reacting more to the tone than the word; but these scientists determined that saying, “Good dog” with that same loving tone lights up their happy brain centers even more, so the two centers work together.

The conclusion of the paper is that dogs did not evolve left-right hemispheric specialization as a result of 15,000 years of domestication, but that BOTH dogs and humans have merely exploited a very ancient division in mammals between emotional processing and cognitive-behavioral processing in the brain: from a 2014 paper by New Zealand psychologist Michael C. Corballis:

Emotions in charge of dog language
Michael Corballis

A right-hemisphere dominance for emotion seems to be present in all primates so far investigated, suggesting an evolutionary continuity going back at least 30 to 40 million years. A left-hemisphere dominance for vocalization has been shown in mice and frogs, and may well relate to the leftward dominance for speech—although language itself is unique to humans and is not necessarily vocal, as sign languages remind us. Around two-thirds of chimpanzees are right-handed, especially in gesturing and throwing, and also show left-sided enlargement in two cortical areas homologous to the main language areas in humans—namely, Broca’s area and Wernicke’s area. These observations have been taken as evidence that language did not appear de novo in humans, as argued by Chomsky and others, but evolved gradually through our primate lineage. They have also been interpreted as evidence that language evolved not from primate calls, but from manual gestures.

All this has relevance to the key principle of this Blog’s paradigm:

The evolution of emotion always precedes and guides the evolution of cognition (ways of knowing and communicating).

The Blog specifically holds that this principle is true for human evolution since the formation of primate groups 52 million years ago: since then, the important changes in the mind were rendered not by adaptations to the physical environment but by adaptations to a series of “reconfigurations” in the social environment—and this social environment has always been (and continues to be) wholly comprised of emotions. So all during the eons of the evolution of both our capacities for language and thought, emotions have always been in the driver’s seat—and they still are!

The key to the Blog’s perspective is the realization that the emotions that direct us spring not from individuals but from the relationships between individuals, because in the process of collective emotions having always been the “environment” for the evolution of our ability to think, they became the source of our thoughts, including yours at this very moment. (All this is slowly and entertainingly rolled out in Old Mind, New Mind)

Tags: , , ,

%d bloggers like this: