The project has targeted linguistic regularities in 8 different linguistic phenomena. In all cases, our team is the first to design and apply artificial language methods, and the first to report behavioral evidence of links between cognition and language in these domains. A selection of our most impactful results are outlined below.
(1) Theories of person (e.g. instantiated in pronoun systems like English 'I', 'you', 'they') typically posit features designed to represent all and only the types of systems found across languages. For example, a pronoun like 'I' has been claimed to be represented as +speaker, –addressee; 'you' as –speaker, +addressee; 'they' as -speaker, -addressee. However, there has been no clear behavioral evidence that people in fact represent person/number in terms of features. We have now provided the first such evidence. Our findings are generally in line with the (sparse) cross-linguistic frequency of different pronoun paradigms, but also challenge aspects of existing theories.
(2) Using artificial language learning experiments, we have shown that adult and child learners use distinct strategies for learning noun classification systems (e.g. grammatical gender): adults relay more on semantic cues to class (e.g. animacy), while children rely more on form-based (phonological) cues (e.g. noun endings). This supports observations from natural language learning, in which children appear to over-rely on phonological cues to class, and suggests a path for how noun classification systems evolve from semantics-based to form-based over time.
(3) In the vast majority of conventionalized languages, nouns and nominal modifiers are ordered such that adjectives are closest to the noun (directly before or after), demonstratives are farthest from the noun, and number words come in between. For example, English has 'these three spotted pencils', and Thai has the equivalent of 'pencils spotted three these'. We have found that across speaker populations, and linguistic modalities (speech and improvised gesture), there is robust cognitive bias favouring orders that conform to this universal template.
(4) One of the best known linguistic regularities relates to how languages order syntactic heads and dependents across different types of phrases. For example, a verb is the syntactic head in a verb phrase, and it takes an object noun as it's modifier (e.g. 'eat an apple'). Similarly, a preposition is the syntactic head in a prepositional phrase, and takes a noun as it's modifier (e.g. 'kick the ball'). The languages of the world tend to consistently order these elements: if the verb is first in the phrase, then so is the preposition, and vice versa. This is called word order 'harmony'. We have found evidence that learners acquiring a miniature artificial language prefer harmonic patterns, across development, and across speaker populations, and across stimulus modalities, suggesting a role for cognition (via learning) in explaining this well-known tendency.
(5) In languages with rich inflectional morphology (e.g. systems of prefixes or suffixes indicating information like person, number, gender, case, etc.), certain ordering regularities have been observed. For example, number tends to be ordered closer to the noun stem than case; person tends to be ordered linearly first, before number. However, sparse cross-linguistic data make it difficult to determine whether these patterns are reliable, and to-date there is no evidence that they reflect pressures coming from the human cognitive system. We have used laboratory experiments with miniature artificial languages to show that indeed, adult learners prefer systems of order that accord with these typological observations, suggesting that patterns of morpheme order are influenced by the biases of language learners.
(6) Most languages tend to form complex words by adding suffixes to the end of word stems (e.g. dog-s), rather than adding prefixes to the beginnings of stems (e.g. un-happy). We have re-assesses existing evidence for a universal suffixing preference by conducting cross-linguistic perceptual similarity judgment experiments. Our studies provide clear evidence for an effect of native language on perception comparing speakers of a predominantly suffixing language (English), with speakers of a pre-dominantly prefixing language (Kîîtharaka). The judgments of these two populations diverge dramatically, calling into question the perceptual origins of this typological skew in prevalence.
