Categorizing Grammar: Differential Effects of Preceding and Succeeding Contextual Cues
Categorizing Grammar: Differential Effects of Preceding and Succeeding Contextual Cues
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语法分类:前后语境线索的不同影响
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发表时间:
2005
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通讯作者:
Akifumi Toksumi
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作者:
H. Murai;Akifumi Toksumi
Categorizing Grammar: Differential Effects of Preceding and Succeeding Contextual Cues Michelle C. St. Clair (msc110@york.ac.uk) Department of Psychology, University of York York, YO10 5DD, UK Padraic Monaghan (pjm21@york.ac.uk) Department of Psychology, University of York York, YO10 5DD, UK Abstract Distributional information has been shown to combine with phonological information in aiding categorisation of words into grammatical categories. There has been debate about the type of distributional information that is most useful in category learning, in particular whether bigrams are sufficient for category acquisition. This paper presents two experiments testing people’s sensitivity to bigram information for categorisation. Sentences were composed of words with category markers occurring either before (Experiment 1) or after (Experiment 2) the category word. Sentences were presented auditorily. Categorical information was learned in both experiments, but the preceding and succeeding distributional cues contributed to learning in different ways. Furthermore, in both cases phonological information assisted the learning of low frequency words. Introduction How do children acquire grammatical categories in their language? In particular, what sources of information are potentially available to enable this process to occur? We present two experiments exploring the interaction between contextual information and phonological information in the child’s environment, and the extent to which these sources can drive learning in artificial grammar learning experiments. Mintz (2002, 2003) has suggested that children acquire grammatical categories based on frequently occurring “frames” in the child’s language environment. Such frames are defined by co-occurring words immediately prior to and succeeding the target word, i.e., a phrase of the form aXb, where X is the category word, and a and b co-occur frequently in text. In child-directed speech in English, one example is the frame “The X is…” where X could be one of several nouns. Mintz (2002) conducted an artificial language study that incorporated frequent frames as markers for categories, and found evidence for categorisation based on this structure. To follow this work, Mintz (2003) conducted corpus analyses of small samples of child directed speech taken from CHILDES (MacWhinney, 2000). Using the 45 most frequent frames in these corpora, Mintz (2003) found that the accuracy of the category groupings based on these frames was extremely high. However, completeness was very low, though was significantly above a random baseline. Monaghan and Christiansen (2004) suggested that this low completeness indicated that frequent frames had very low coverage and that this was consequently a poor source of information for categorisation. Instead, they suggested that bigram information could provide richer cues about category. The trigram information in the aXb frames was conflated with aX (e.g., “The X”) and Xb (e.g., “X is”) bigrams, and learning in Mintz (2002) may have been driven by information at the bigram level only. Monaghan and Christiansen (2004) replicated Mintz’s (2003) corpus analyses, finding high accuracy and low completeness for aXb frames, and slightly lower accuracy but much higher completeness for bigram information: categorizing 69.9% of the words, compared to only 14.3% using the aXb frame. In addition, Monaghan and Christiansen (2004), in neural network models trained to learn grammatical categories, found that when the aXb frame was decomposed as aX and Xb then learning increased. Yet the finding that bigram information is potentially useful for category learning is not the same as demonstrating that it is useable. However, Valian and Coulson (1988) constructed an artificial language where bigram information was exploited for category learning. Sentences were of the form aAbB, where a and b were high frequency marker words, and A and B were sets of category words. They found that novel aAbB sentences were preferred to those that violated the bigram information: *aBbA. In an extension of this study, Monaghan, Chater, and Christiansen (2005) found direct evidence for words from the same category being grouped together. Both these studies have explored the learning of aX bigram information, but as yet there is no evidence that categories can be learned from Xb bigrams. Furthermore, these artificial language studies were conducted with sentences presented visually. There may be a difference in categorisation performance when the modality of presentation is altered. In an artificial language learning experiment, Onnis, Christiansen, Chater, and Gomez (2003) found a similar trend in visually presented stimuli compared to auditory presentation, though the effect was reduced in the former. Distributional information is not the only cue determining grammatical categorisation; phonological information has also been implicated in the learning of grammatical and gender categories (Braine et al., 1990; Brooks, Braine, Catalano, Brody, & Sudhalter, 1993). Indeed Braine (1987) has claimed that support from phonological information is vital for categories to be learnable. Kelly (1992) has shown