2. Songbirds and language

Wikis > Chapter 19 - Bird(songs) and Language > 2. Songbirds and language

There are over 5000 species of songbirds, all of which are of the suborder of Passeri. Their method of communication systems are songs and simple calls. They use calls for simple functions and more elaborate songs to find mates. In the first wiki chapter, the design features of Charles Hockett were introduced. In this section, we review two of them, cultural transmission and syntax, and investigate whether they are present in songbirds’ communication.

2.1 Cultural transmission

An important commonality between songbirds and humans involves the way they learn to communicate.

Firstly, they both exhibit sensitive periods in learning. While scientists do not agree on any concrete period, the general consensus is that it is during the first few years of our lives (Hakuta, Bialystok & Wiley, 2003). But for songbirds, it occurs during their first few months. During this critical period, the volume and connectivity of their brain cells responsible for song learning and production increases (Barker, 2017). If a songbird is not exposed to any birdsong during the critical period, it will still be able to sing, but only simple songs. Secondly, for their songs to develop well, they require an older bird to teach them to sing, similar to how infants require exposure to human vocalizations when they are young (Mehler et al., 2000).

Their song development occurs in two overlapping stages. The first stage, roughly 15 to 60 days after the birds hatch, involves learning songs from older “tutor” male songbirds. The second stage, occurring around 30 to 90 days after hatching, has the birds practicing, refining, and memorizing the song that they will sing for life (Barker, 2017).

Even though hatchlings learn their songs from older male songbirds, occasionally, a songbird may sing a note incorrectly. These variations from generation to generation lead to changes in their songs (Slater, 2012).

2.2 Syntax

There have been studies carried out which analyse bird songs. Berwick et al (2011) analysed the syntax in bird songs and compared them to human language. In the paper, the researchers claimed that songs had fixed sequences. The songs either contained only sporadic variation, or contained more variable sequences where a song element might be followed by several alternatives.

Figure 1. Spectrogram of a typical Zebra Finch song (Berwick et al., 2012)

Figure 1 shows that there is a clear hierarchical structure to their bird song. Their analysis showed that songs often started with introductory notes, as indicated by the ‘i’ in the figure before the actual song begins. The songs had distinct ‘notes’ which could be combined as particular sequences into syllables, syllables into ‘motifs’, and ‘motifs’ into ‘bouts’. There is a clear similarity to the hierarchical structure in the human language. In human language, we take individual phonemes (‘notes’), combine them into syllables (‘syllables’), and then into words (‘motifs’). Combining all the words together eventually forms a sentence (‘bouts’). Thus, it can be posited that bird songs consist of chains of discrete acoustic elements arranged in a particular temporal order. What this means is that they have a finite number of sounds which can be combined to form endless different meanings, a feature of human language known as productivity. Therefore, if birds have this ability it must mean they have language too.

Their capacity for productivity was demonstrated in a study by Suzuki et al. (2016) which looked to analyse the syntax of the calls of the parus minor. In one of their experiments, they played recordings of one their calls in two different orders: ABC-D (natural sequence) and D-ABC (artificially reversed sequence). The ‘D’ part of the call is used by the caller to gather the other birds to them. When the first call was played, the birds would fly close to the speaker which played the sound. On the other hand, when the artificially reversed sequence was played, the birds only responded occasionally. This experiment is evidence that birds may have a compositional syntax.

However, while the experiment was able to provide evidence for syntactic structure in parus minor bird songs, it is inaccurate to say that it is comparable to human language because they lack one fundamental aspect: semantics.

Songbirds are only able to convey limited intentions (Berwick et al., 2011). For example, if there was a predator approaching them, they would not be able to describe what the danger is, like what type of animal it is or how many there were. They would only be able to convey notions of flying or danger.

Thus, Berwick et al (2011) concluded that they do not have grammatical syntax but only phonological syntax. This means that there are only a certain set of units that can be arranged in particular ways, and these arrangements may not necessarily create new meanings.

Another reason bird communication cannot be considered language is that their system is not unbounded in length and structure.

In human language, sentences can be embedded within other sentences and recombined endlessly to form longer and longer sentences. Take for example the sentence “the hunch that the serial killer who the waitress had trusted might hide the body frightened the FBI agent into action” (Thomas, 1995), there are three clauses: “who the waitress had trusted” which is embedded in the clause “that the serial killer might hide the body” which is then embedded in the main clause “the hunch frightened the FBI agent into action”. This exhibits the open-ended novelty that Wilhelm von Humboldt famously called the “infinite use of finite means”(Chomsky, 1992), and a cornerstone in what human languages were.

Birds on the other hand have a limited ability to construct phrases. They are mostly limited to an AnBn phrase structure (Hauser et al., 2002). Thus, although songbird songs share some similarities with human language, they are not advanced enough to be considered language as they also lack other key design features of human language.