Budgerigars and zebra finches differ in how they generalize in an artificial grammar learning experiment

Abstract

The ability to abstract a regularity that underlies strings of sounds is a core mechanism of the language faculty but might not be specific to language learning or even to humans. It is unclear whether and to what extent nonhuman animals possess the ability to abstract regularities defining the relation among arbitrary auditory items in a string and to generalize this abstraction to strings of acoustically novel items. In this study we tested these abilities in a songbird (zebra finch) and a parrot species (budgerigar). Subjects were trained in a go/no-go design to discriminate between two sets of sound strings arranged in an XYX or an XXY structure. After this discrimination was acquired, each subject was tested with test strings that were structurally identical to the training strings but consisted of either new combinations of known elements or of novel elements belonging to other element categories. Both species learned to discriminate between the two stimulus sets. However, their responses to the test strings were strikingly different. Zebra finches categorized test stimuli with previously heard elements by the ordinal position that these elements occupied in the training strings, independent of string structure. In contrast, the budgerigars categorized both novel combinations of familiar elements as well as strings consisting of novel element types by their underlying structure. They thus abstracted the relation among items in the XYX and XXY structures, an ability similar to that shown by human infants and indicating a level of abstraction comparable to analogical reasoning.artificial grammar learning | rule learning | auditory perception | songbirds | parrots O ne of the critical features of language learning is the ability to abstract the grammatical structure from spoken language. Such abstraction allows humans to learn about regularities in their native language and to generalize these regularities to novel input. This ability is examined in a standardized way in artificial grammar learning experiments, in which humans are exposed to strings of meaningless sounds (e.g., arbitrary speech syllables) organized according to a specific grammatical structure. Several studies have shown that the ability to abstract the underlying structure from such stimuli is present in young infants (1-5) in both the acoustic and the visual domain (6-8). This domain generality and its presence at a very early age have given rise to the notion that this cognitive ability may have preceded language evolution and served as a basis for present-day linguistic complexity. If so, it raises the question to what extent this ability is confined to humans or also can be found in nonhuman animals. In this context, comparative studies on nonhuman animals are needed to reveal the level of abstraction they are able to achieve in artificial grammar learning tasks. This information might provide hypotheses about how and why the more complex human grammatical competences have arisen. The current study addresses whether two bird species, the...

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Relative salience of syllable structure and syllable order in zebra finch song

“…However, these results do suggest an interesting avenue for further comparative investigation on the neural basis of fine structure and envelope processing in birds. Another recent perceptual study of these zebra finches and budgerigars also showed a difference in both capability and strategy in the processing of sequences of song elements (Spierings and ten Cate 2016). …”

Statistical learning in songbirds: from self-tutoring to song culture

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