Information Experiment with Bird Calls

For this blog post I decided to look at an experiment on the syntactic structure of bird calls and found this article, “Experimental evidence for compositional syntax in bird calls.” The authors explain that human language has two hierarchical levels of syntactic structure: phonology, which combines meaningless elements to form meaningful words, and compositional syntax, where a person combines different words to form more complex expressions. While phonology has been documented in animal communication systems, this experiment provides “the first unambiguous experimental evidence for compositional syntax in a non-human vocal system” (Suzuki et al.).

As a controlled variable, they specifically investigated the Japanese Great tit (Parus minor, Paridae) to determine whether different note types have “distinct meanings to receivers when produced separately and, if so, whether receivers extract a compound meaning when both elements are combined (compositional syntax)” (Suzuki et al.). Great tits produce “chicka” calls composed of A, B, C, and D notes, and typically A, B, and C notes are combined and the D note is separate. The researchers hypothesized that the combination of ABC and D calls into ABC-D calls that represent semantically compositional syntax.

In designing their experiment, they created two playback experiments, another controlled variable. In the first, they examined whether tits extracted meaning from hearing combined ABC-D calls. The dependent variable is the tit’s response to the vocal call. The researchers explained the bird could respond in two different ways. They could show a combined response to ABC-D calls, combining the distinct behaviour produced when they hear ABC calls with behaviour made by D calls because they recognize ABC-D as a single meaningful unit. Or, they may produce two distinct behavioural responses for ABC calls and D calls. This would be the independent variable, the bird’s response. They also added an additional control of using background noise to determine the bird’s response to noise other than the calls.

They compared responses of tits with playbacks of natural (ABC-D) and artificially reversed (D-ABC) sequences. The researchers found that tits extract different meanings from ABC and D calls, and compound meanings from ABC-D calls. They noticed that the tits combined behaviour when hearing the natural ABC-D sequences, but failed to produce a compound response to the artificially reversed call. I find this really interesting in terms of learning about communication structures and how sounds are combined to create meaning. While this may not be necessarily be related to what we are discussing in class, I think it’s important to look at how information is conveyed through various means. Even if we as humans may not be able to understand what is said, we can discern responses to information and can interpret what is the meaning.

Source

Suzuki, Toshitaka N., David Wheatcroft, and Michael Griesser. (March 8, 2016). “Experimental evidence for compositional syntax in bird calls.” Nature Communications 7.