Why Form-Meaning Mappings Are Not Entirely Arbitrary in Language

Why Form-Meaning Mappings are not Entirely Arbitrary in Language Padraic Monaghan (pjm21@york.ac.uk) Department of Psychology, University of York York, YO10 5DD, UK Morten H. Christiansen (mhc27@cornell.edu) Department of Psychology, Cornell University Ithaca, NY 14853, USA application of (destructive) force to something:bash, clash, thrash, trash, slash, mash, dash, etc. – the psychological reality of which has been confirmed through priming experiments (Bergen, 2004). Moreover, as we show below, systematic mappings also exist between words and their lexical categories, and these go well beyond the effects of morphological affixing. In this paper we present a simple model of word learning in order to investigate the circumstances under which systematic form-meaning mappings may be advantageous for language learning. Abstract We discuss two tasks that the child must solve in learning their 1 language: identifying the particular meaning of the word being spoken, and determining the general category to which the word belongs. We present a series of simple language learning models solving these two tasks. We show that learning the precise meaning of the word is more easily accomplished if there are arbitrary mappings between the spoken form of words and their meanings, when these words are presented with contextual information. We also show that learning general categories is best achieved when there is systematicity in the mappings between forms and categories. We present corpus analyses of English and French indicating that there is both arbitrariness and systematicity in language, and suggest that this co-habitation is a design feature of natural languages that benefits learning. The Child’s Dual Task Introduction Since Saussure (1916), the relationship between the sound and the meaning of words has been regarded as largely arbitrary. Indeed, the arbitrariness of form-meaning mappings has long been highlighted as a design feature of human language (e.g., Hockett, 1960). Recent support for arbitrariness has come from computational simulations by Gasser (2004), who demonstrated that, for large vocabularies, there is a learning advantage for arbitrary form-meaning relationships. Because systematic pairings of forms and meanings require strong constraints on the space of possible pairings (e.g., a particular onset phoneme is restricted to only co-occur with a particular facet of meaning) it is only possible to encode efficiently a relatively small number of words. In contrast, arbitrary mappings between form and meaning impose fewer constraints and therefore permit the learning of a large and extendable vocabulary, which is the hallmark of human language. Though the general picture is one of arbitrariness between the individual phonological form of a word and its meaning (see Tamariz, 2005 for an estimate of the correlation), some systematic mappings do exist in natural language; for example, expressives in Japanese and Tamil show evidence of a systematic form-meaning mapping (Gasser, Sethuraman, & Hockema, in press). In English certain groups of words display similar sound symbolism – such as, -ash which tends to occur at the end of words indicating the Throughout this paper, we employ the epicene they: “A person cannot help their birth”. Thackeray, W.M. (1848). Vanity fair. London: Punch. The context of the utterance of a word (e.g., situational, gestural, verbal co-occurrence) provides a great deal of information about the general ballpark meaning of the word (Tomasello, 2003). Given this contextual information, then, would it be more conducive to learning the pairing between the spoken form of a word and its precise meaning if there is a correlation between the spoken representations and the output representations, or if there is no, or little, correlation? We hypothesise that if each word within a general region of semantic space was very different in its spoken form to other words then this would benefit the learning of the mapping – the learner has more individual sources of information to exploit in determining the mapping. If there is a correlation, then precise and subtle differences between the spoken forms of words have to be attended to in order to identify the exact intended meaning. As an example, imagine the situation where a child is observing animals milling around in a farmyard. In English, the child hears the words “cow”, “sheep”, “goat”, and “chicken”, and is required to form a mapping between each word and each animal. The words in another language, SystemEnglish for these same animal referents are “bim”, “bin”, “bing”, and “pim”. We predict that the child learning SystemEnglish is going to find the task significantly more difficult, partly because subtle differences between words have to be attended to, and partly because such differences may be over-ruled by the noise present in the auditory environment, which may obliterate the distinctions entirely. Indeed, although 12-month-old children can distinguish between minimal pairs of sounds such as “bin” and “bim”, they are unable to associate these terms with distinct referents at the age of 14 months. However, children can perform this association when the words are more phonologically distinct (Werker, Fennell, Corcoran, & Stager, 2002).