The Evolution of Speech and Language: A Comparative Study of Humans and Primates, Apuntes de Psicolingüística

¡Descarga The Evolution of Speech and Language: A Comparative Study of Humans and Primates y más Apuntes en PDF de Psicolingüística solo en Docsity! Psycholinguistics, English language Acquisition and Learning Dr. Ana Laura Rodríguez Redondo ____________________________________________________________________ 1 (Adapted from. Sedivy, J. 2014. Language in Mind. An Introduction to Psycholinguistics. Sunderland, Mass: Sinuaer Associates. Pp. 31-37) The Evolution of Speech The ability to speak: Humans versus the other primates In the previous sections, we explored two separate skills that contribute to human language: (1) the ability to use and understand intentional symbols to communicate meanings, perhaps made possible by complex social coordination skills; and (2) the ability to combine linguistic units to express a great variety of complex meanings. In this section, we consider a third attribute: a finely tuned delivery system through which the linguistic signal is transmitted. To many, it seems intuitively obvious that speech is central to human language. Hockett believed human language to be inherently dependent on the vocal-auditory tract, and listed this as the very first of his universal design features. And, just as humans seem to differ markedly from the great apes when it comes to symbols and structure, we also seem to be unique among primates in controlling the capacity for speech-or, more generally, for making and controlling a large variety of subtly distinct vocal noises. […] A comparative glance at the vocal apparatus of humans versus the great apes reveals some striking differences […] the human larynx rests much lower in the vocal tract than that of chimpanzees. This creates a roomier mouth in which the tongue can move around and make acoustically distinct sounds. We also have a very broad tongue that curves downward toward the throat. Chimpanzees, whose tongues rest flat in their long and narrow oral cavity, have more trouble producing sounds like the vowels in bead or boo. The distinct shape of our vocal tract comes at a tremendous cost: for the great apes, the height of the larynx means that they can breathe and swallow at the same time. We can't, and so quite a few human beings die as a result of choking on their food or drink. It's implausible that this potentially lethal trait would have evolved if it didn't confer a benefit great enough to outweigh the risk. Some researchers have argued that speech is precisely such a benefit, and that (genetically speaking) our species accepted some risk of choking as a fair trade for talking (Lieberman et al., 1969). Still, the link between speech and a lowered larynx is not clear. Many animals can and do actively lower their larynx during vocalization, possibly as a way to exaggerate how large they sound to other animals (see, e.g., Fitch, 2010). In any case, having the right anatomy for speech is only part of the story. Somewhere in the evolutionary line between chimpanzees and us, our ancestors also had to learn to gain control over whatever articulatory equipment they had. As an analogy, if someone gives you a guitar, that doesn't make you a guitar player (even if it's a really terrific guitar). You still have to develop the ability to play it. And there's reason to believe that, aside from any physical constraints they might have, non-human primates are surprisingly lacking in talent when it comes to manipulating sound. More specifically, they appear to have almost no ability to learn to make new vocal sounds-clearly a key component of being able to acquire a spoken language. […] The failure of primates to learn to produce a variety of vocal sounds is all the more mysterious when you consider that there are many species of birds genetically very distant from us-who have superb vocal imitation skills. Songbirds learn to reproduce extremely complex sequences of sounds, Psycholinguistics, English language Acquisition and Learning Dr. Ana Laura Rodríguez Redondo ____________________________________________________________________ 2 and if not exposed to the songs of adults of their species, they never get it right as adults, showing that much of their vocal prowess is learned and not directly programmed into their genes (Catchpole & Slater, 1995). Many birds such as ravens or mockingbirds easily mimic sounds not naturally found among their species-for instance, the sounds of crickets or car alarms. And parrots are even able to faithfully reproduce human speech sounds-a feat that is far beyond the capabilities of the great apes- despite the fact that the vocal apparatus of parrots is quite unlike our own. This suggests that the particular vocal instrument an animal is born with is less important than the animal's skills at willfully coaxing a large variety of sounds from it. Sophisticated vocal learning is increasingly being found in other non-primate species. For example, seals, dolphins, and whales are all excellent vocal learners, able to imitate a variety of novel sounds, and there are even reports that they can mimic human speech (e.g., Ralls et al., 1985; Ridgway et al., 2012). Recently, researchers have found that an Asian elephant is able to imitate aspects of human speech (Stooger et al., 2012). As evolution researcher Tecumseh Fitch (2000) puts it, "when it comes to accomplished vocal imitation, humans are members of a strangely disjoint group that in eludes birds and aquatic animals, but excludes our nearest relatives, the apes and other primates." Why are other primates so unequipped to produce speech sounds? Several researchers (e.g., Jürgens et al., 1982; Owren et al., 2011) have argued that not all vocalizations made by humans or other animals are routed through the same neural pathways. They've pointed out that both humans and other primates make vocalizations that come from an affective pathway-that is, these sounds have to do with states of arousal, emotion, and motivation. The sounds that are made via this pathway are largely inborn, don't require learning, and aren't especially flexible. Among humans, the noises that crying babies make would fall into this category, as would the exclamations of surprise, fear, or amusement that we all emit. Notice that, while languages have different words for the concept of a dog, laughter means the same thing the world over, and no one ever needs to learn how to cry out in pain when they accidentally pound their thumb with a hammer. Non-human primates seem to be, for the most part, limited to vocalizations that are made by the affective pathway, and the alarm calls of animals such as the vervets are most likely of this innate and inflexible affective kind. But humans (and some other animals, including songbirds and aquatic mammals) can also make vocal sounds via a cognitive pathway. These sounds usually involve a great deal of auditory learning before they can be reliably produced, take practice, and are highly malleable. Language sounds (unlike giggles or cries of terror) are the result of the cognitive pathway and are, under this view, different from ape vocalizations not just in variety and complexity, but in their fundamental nature. Language without speech It would appear, then, that perhaps the sharpest discontinuity between human and non-human primates lies in the ability to produce the speech signal by which linguistic meaning is usually conveyed. But here, the evolutionary story has a very interesting twist: as it turns out, Hockett was wrong, and human languages aren't universally spoken. It's true that speech is the default mode along which to transmit language-in every known society whose members have normal hearing, people communicate by shaping the noises that come out of their mouths. But when humans are deprived of their usual auditory powers, they can readily adapt language and produce it by means of gesture