Lexical categories or frequency effects? A feedback from quantitative methods applied to psycholinguistic models in two studies on Italian.
Authors: Francesca Franzon, Giorgio Arcara, Chiara Zanini (Università di Padova, San Camillo IRCCS, 2016)
Topic: Lexical and Semantic Resources and Analysis

Abstract
We examined two issues concerning Italian Number morphology: the phenomena related to mass and count nouns and to the plural dominance. By taking into account quantitative data from corpora and subjective frequency ratings in three mixed effect models, we found that differences in participants’ performance in two lexical decision tasks could be better captured as differences in frequency rather than in terms of effects of lexical categories.

Introduction
The role of frequency in lexical retrieval is well known for what concerns psycholinguistic studies AUTHOR: the higher the frequency of a word, the faster its retrieval. Generally, the singular form of a noun is more frequent than the corresponding plural, and thus retrieved faster. However, some nouns (e.g. stelle, ‘stars’) do occur more frequently in the plural than in the singular: the phenomenon is known as plural dominance. Plural dominant nouns are in fact accessed faster in the plural form than in the singular. Since such nouns are not identifiable as a homogeneous group by means of some semantic features, the phenomenon has been explained as a mere effect of the frequency of occurrence of the forms AUTHOR. While the plural dominance seems to be unrelated to grammatical constraints, another phenomenon involving Number morphology seems to be grammatically grounded instead, namely the mass-count issue AUTHOR. Nouns referring to countable entities are called ‘count nouns’ (anello, ‘ring’), nouns referring to uncountable entities are called ‘mass nouns’ (burro, ‘butter’). Some constraints rule the possibility for the two types of nouns to occur in some morphosyntactic contexts, for example count nouns cannot occur in the singular after a quantifier (*molto anello, ‘much ring’), while mass nouns cannot occur with numerals or the indeterminate article (*un burro, ‘a butter’). For what concerns Number morphology, mass nouns should occur only inflected in the singular (but for a deeper discussion, see i.a. AUTHOR. Previous lexical decision tasks have pointed out to some differences in the processing of count nouns with respect to mass nouns, which would require longer response times (RTs) AUTHOR. In the light of these results, it has been proposed that an additional lexical feature has to be computed for mass nouns as compared to count nouns. While psycholinguistic studies on plural dominance have relied on relative frequency of singular and plural forms in the selection of stimuli and in results analysis, even the most recent experimental studies on the mass-count issue have not quantified the actual occurrence of the experimental stimuli in mass context and in count context: nouns have rather been assigned to a mass or to a count category on the basis of the experimenters’ judgments. Quantitative data on syntactic contexts can instead provide a better estimate of the frequency of use of nouns as countable or uncountable: in the present study we relied on the actual occurrence of nouns in the different syntactic contexts in assigning them to the “mass” or to the “count” experimental list. We will describe and put into comparison two lexical decision tasks, concerning the phenomena of mass-count and of plural dominance respectively. We will explore the possibility that the mass-count effects described in psycholinguistic literature could be better explained in terms of frequency of occurrence, as it is recognized by most literature with respect to plural dominance. We hypothesize that the frequency of occurrence of the word form (inflected in the singular or in the plural) will predict the RTs in lexical decision tasks contrasting mass and count nouns, as well as in the ones concerning the plural dominance issue. The frequency of occurrence will be measured by means of two subjective frequency rating studies and in the corpus ItWaC AUTHOR. We will rely on quantitative measures to categorize experimental stimuli. Measures of plural dominance of nouns will be based on the ratio between their occurrence in the plural and in the singular; the mass and count experimental nouns will be categorized considering their distribution with respect to mass and count morphosyntactic contexts.

Conclusion
In this study we applied quantitative methods in the selection of experimental stimuli used in the two lexical decision tasks. In both tasks, results from the three models showed effects of subjective frequency and corpus frequency but not of category in written word recognition. For what concerns the plural dominance issue, this result was in line with previous literature. For what concerns the mass-count issue, our results are unexpected instead. Remind that frequency of occurrence in mass and count contexts was used to avoid biases in categorization of stimuli. Nevertheless, we did not observe differences in RTs between the two so categorized groups of nouns. Thus, we suggest that there is no need to postulate the computation of a lexical feature related to countability or uncountability in nouns. We propose that the fact that a noun is considered “mass” is better described as an epiphenomenon of the distribution of noun with respect of syntactic contexts. However the possibility for a noun to occur in the different syntactic contexts does not predict lexical decision RTs: frequency, as measured in the corpus and by the rating study, is the predictor of the lexical access times with respect to words presented in isolation. In this sense, the mass-count issue is similar to the plural dominance phenomenon: even in that case, there is no need to assume the presence of a feature marking plurality, as the frequency of the inflected form is sufficient to account for the observed effects in lexical decision tasks. The frequency of occurrence of nouns considered as a continuous variable is a better predictor of RTs than a distinction attributed to alleged lexical categories both in the case of phenomena seemingly unrelated to core grammar rules, like the plural dominance, as well as in phenomena that have traditionally been described as grammar based, like the mass-count issue.