I am teaching "Human Nature and Human Values" again and that always means consuming a lot of recent research. One study I just digested into PowerPoint slides concerned the development of language by infants. Back when I was (briefly) a psychology major (late 1970's), I was taught that language is acquired by mere power of association. When an infant is exposed to one auditory stimulus (a word) in frequent conjunction with another (an object), then the infant learns that word for that object. That is the Standard Social Science Model. All social behavior is explained by reference to other social behavior.
For that model to be confirmed, it should be the case that any sufficiently recognizable auditory stimulus would do. For example, a buzz or buzz and click should be learned as a word for nose, if that is what the infant is taught.
A recent study indicates that only certain kinds of auditory stimuli trigger the learning of words and that these stimuli in conjunction with visual examples triggers categorization in infants as young as three months old. I find that very exciting.
The study is "Nonhuman primate vocalizations support categorization in very young human infants" by Alissa L. Ferry, Susan J. Hespos, and Sandra R. Waxman (PNAS | September 17, 2013 | vol. 110 | no. 38 | 15231–15235). Ferry et. al. exposed infants to images of dinosaurs in conjunction with a range of auditory signals, including tones and backward human speech. Then they showed the subject two images, one of which was a new dinosaur and the other a fish. They measured learning by whether the infant gazed at the dinosaur rather than the extra-categorical image.
It turns out that tones and backward speech had no effect. The infants did not associate these auditory stimuli with categories of objects. Nor did they respond to the visual stimuli alone, in the absence of any auditory stimulus. However, when the infants were exposed to coherent human speech or nonhuman primate vocalizations along with the images in the first stage of the test, then they recognized the novel dinosaur in the second stage of the test.
That the infants responded to human vocalization in the first stage but not to tones or backward speech suggests that they are primed to tune in to certain stimuli but not others. This indicates an evolved psychological mechanism for learning language. That they recognized a new member of a previously presented category after only a very brief exposure indicates that this mechanism, far from being a mere power of association, includes a power of forming mental categories. At three months of age. That their power of categorization was triggered both by human speech and nonhuman vocalization indicates that this mechanism has deep evolutionary roots, going back well before the emergence of human beings on this planet.
The Socratic philosophers were onto this more than two thousand years ago. Plato knew that human beings could form altogether artificial categories, such as "all numbers except 17". That capacity exists, however, because it reflects and exemplifies something essential about the world we live in. The world sorts itself into categories: rocks and living creatures, plants and animals, dinosaurs and mammals, horses and cows.
Evolutionary theory wonderfully enriches the Socratic idea. The ability to recognize categories of things is not only a consequence of evolution is part of the dynamic of evolution. One theory of what a biological species is turns precisely on species recognition. Horses are horses and not cows because they recognize horses as potential mates. That horses can breed with donkeys indicates that the two species have split but remain just close enough to produce mules.
The Greek word logos was pregnant with meaning. It meant first the human power of speech. It was extended to include human reason and the truths that reason could reveal. Later, it came to mean the coherence of the intelligible kosmos. Philology recapitulates metaphysics, in Greek philosophy and evolutionary psychology. In the beginning was the word.