Science

What does the fox say?

today2019.08.01. 7

Background

As children we are taught the sounds of animals – the chatter of a monkey, the squeak of a mouse, the bark of a dog, and many others. Often, we try to communicate with our nonverbal companions – be it a friendly cat or an annoying mosquito. At times these animals seem to understand us, and other times it feels as though we understand them. But do these animals have language? Do they truly communicate, or do they only make a few meaningful sounds?

Table of contents

Defining language

Language is a system of communication using sounds and/or signs to convey meaning. Human language possesses certain characteristics, including arbitrariness, productivity, and semanticity. Arbitrariness refers to the random assigning of words to meanings. If you repeat the word “song” many times (as you probably did as a child), you may begin to wonder if it is a word at all. You experience this phenomenon because there is nothing meaningful in the sounds “s-o-n-g”. Language is considered productive when it can be used to express infinitely many ideas which are understandable to others. This is aided by its semanticity – each word carries a specific meaning, although it may be context-specific, such as the phrase “hot dog”. Additionally, human language is versatile in that it can be used to describe events in times and places other than the present.
Humans learn language through exposure. Babies imitate their parents, beginning with meaningless babble and eventually learning to vocalize syllables and then words. Without any example, a human child would not learn to speak, and would eventually lose the capability of learning [1]. Fortunately, with relatively little assistance, children learn and develop full speech as long as they are exposed to language in their environment.
Animals, by comparison, have less complex linguistic systems. Most have only a limited number of sounds which correspond to important events and experiences and which are memorized from a young age. Monkeys may be social creatures, but studies of their language have revealed little more than a system of calls to name different predators [2]. Their vocal tracts are capable of human speech, but they likely lack the mental ability or interest to produce language [3].

Hunger: the great motivator

Domestic creatures, such as dogs and cats, tend to communicate verbally more than wild animals. Research suggests that this behavior is the result of centuries of breeding and their desire to communicate with humans, often in exchange for food. Dogs can distinguish between different types of barks and growls, whether they indicate play, feeding, or danger. But the wolves from which they were bred use smells and signals more than howls [4]. Similarly, cats meow at humans, especially around lunchtime, but not at other cats. Some animals, such as chimpanzees and dogs, can be taught to respond to human vocabulary, but it is a slow process that yields some understanding but no speech.
Like with all language rules, there is always an exception. Parrots are able to imitate human speech and have demonstrated the ability to learn as many as 100 words [5]. More than just mimicry, they use the words in context and are able to create unique words for new objects and recognize words they cannot pronounce. They also have the capacity to remember unused words for a year or longer, such as for seasonal fruits.

Birdsong linguistics

Recent findings suggest that birds’ vocal abilities may be important for more than just food appreciation. Like human children, some species of birds have demonstrated the ability to learn by listening and repeating. Additionally, birdsong has syntactic structure comparable to that of human language, and the neural patterns involved in learning and producing birdsong are similar to how babies learn to speak.
In general, birdsong consists of several notes which can be combined into syllables, syllables into motifs, and motifs into songs, a hierarchical organization similar to human language. Some birds are limited to a few fixed sequences, while others have more varied songs. For example, the Japanese tit knows eleven notes which can be combined much as letters are to form various predator alarm calls [6]. The combinations are highly varied even in limited contexts, suggesting a greater level of complexity than the warning cries of other animals. Different combinations of calls result in differing behavioral reactions from the birds. One call elicits watchfulness while another causes the birds to approach the caller. Combining these calls in a specific order prompts both behaviors, while the reverse ordered call is ignored. This might be the equivalent of hearing your mother call dinnertime before she tells you to stop having fun, as opposed to the reverse. However, it could also be an indication of meaningful syntax, where the information of the call depends on the order of the notes. It may also be a purely phonetic difference.
As with any potential scientific finding, there is an opposing camp to the theory that birdsong could hold the key to understand language and the neuronal basis of language learning. While birdsong demonstrates neural and linguistic similarities to human speech, it lacks words and semantics, and some question whether it should be considered true language [7]. The phonology of both may be similar, but human language is more complex in that it is able to produce new behavioral contexts, unbounded by length and structure restrictions. Moreover, birdsong is context-dependent rather than word-dependent. The meaning of each song depends on the situation, such as mating or fleeing, and the birds have not demonstrated a natural ability to create new meanings. But whether it compares to human language or not, neural controls of birdsong may still provide research material regarding a very important area of the brain: the basal ganglia, which is a key component for spoken language [8].

Birds of a feather..

The stages birds go through while learning to sing are surprisingly similar how infants learn to speak. The first step is copying older birds – just as babies copy caretakers -, modifying the song until the auditory feedback matches the model. Young birds begin by singing in their sleep, a sound that is similar to when humans try to sing a song they don’t know the words to. During this sub-song phase, which corresponds to a babbling phase in human infants, the chicks train the muscles necessary for sound production, while the auditory feedback of hearing oneself helps adjusting the song to the memorized sounds. Overtime this improves into a recognizable imitation and the song becomes a habit, stable and unchanging.[9]
Parallels are also found in the nervous system of humans and songbirds. Both have evolved brain areas necessary for meaningful vocalizations and similar neural mechanisms might be involved in these functions. The motor pathway, allowing for the acquisition and production of songs and a cortical pathway required for learning new songs [10]. If the basal ganglia are damaged, young birds will fail to develop mature songs while adults will lose the ability to creatively alter their songs. Similarly, when the human basal ganglia are damaged, it leads to dysfunctions in speech. As the bird learns to sing, the related neural cells, located in both hemispheres, not only grow and form new connections, they also increase in number. While some birds show right or left dominance, as do most humans, many are able to use both sides for birdsong, sometimes independently. When a bird sings, it uses either its motor memory of learned songs or its basal ganglia to create new songs. Just as humans learn new pick-up lines, adult songbirds develop new songs each season to attract mates. During this process, they generate new neurons, challenging the view that brain cells once lost can never be replaced and the classic insult “birdbrain” [10].

But what does the fox say?

There is currently no research into the science of fox communication, as these adorably furry creatures have even less to say than dogs. But the functional and neurological mechanisms behind birdsong is gaining deserved attention with its similarities to human. Vocal learning and the possible applications that it may have for treatment against autism, stuttering and genetic disorders of speech. Future research into birdsong may uncover ways to generate new brain cells and find treatments to such conditions [11]. While the fox may not have much to say, as far as we know, the songbird has a lot to sing to neuroscientists in the coming years.

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References

1.  Lapointe, L. (2005). Feral children. Journal of medical speech-language pathology 13(1): VII-IX.
2. Schlenker, P., Chemla, E., Zuberbuhler, K. (2016). What do monkey calls mean? Trends in Cognitive Science 20(12): 894-904. Doi: 10.1016/j.tics.2016.10.004
3. Fitch, W., de Boer, B., Mathur, N., Ghazanfar, A. (2016). Monkey vocal tracts are speech-ready. Science Advances 2(12). Doi: 10.1126/sciadv.1600723
4.  Siniscalchi, M. et al. (2018). Communication in dogs. Animals (Basel) 8(8): 131. Doi: 10.3390/ani8080131
5.  Pepperberg, I. (1994). Vocal learning in grey parrots (Psittacus erithacus): Effects of social interaction, reference, and context. The Auk 111(2): 300-313
6. Suzuki, T. (2018). Call combinations in birds and the evolution of compositional syntax. PLoS Biol. 16(8): e2006532. Doi: 10.1371/journal.pbio.2006532
7.  Berwick, R. et al. (2011). Songs to syntax: the linguistics of birdsong. Trends in Cognitive Sciences 15(3): 113-121. Doi: 10.1016/j.tics.2011.01.002
8.  Lanciego, J., Luguin, N., Obeso, J. (2012). Functional neuroanatomy of the basal ganglia. Cold Spring Harbor Perspectives in Medicine 2(12). Doi: 10.1101/cshperspect.a009621
9.  Doupe, AJ., Kuhl PK. (1999). BIRDSONG AND HUMAN SPEECH: Common Themes and Mechanisms. Annual Review of Neuroscience 22(1): 567-631. Doi.org/10.1146/annurev.neuro.22.1.567
10. Nottebohm, F. (2005). The neural basis of birdsong. PLoS Biol 3(5): e164.
11. Brainard, M., Doupe, A. (2013). Translating birdsong: songbirds as a model for basic and applied medical research. Annu Rev Neurosci 36: 489-517. Doi: 10.1146/annurev-neuro-060909-152826

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