Grammatical Class Effects in Production of Italian Inflected Verbs
Authors: Maria De Martino, Azzurra Mancuso, Alessandro Laudanna (Università di Salerno, 2018)
Topic: Lexical and Semantic Resources and Analysis

Abstract
We report a picture-word interference (PWI) experiment conducted in Italian where target verbs were used to name pictures in presence of semantically related and unrelated distracters. The congruency of grammatical class between targets and distracters was manipulated and nouns and verbs were used as distracters. Consistently with previous studies, an expected semantic interference effect was observed but, interestingly, such an effect does not equally apply to target-distracter pairs sharing or not grammatical class information. This outcome seems to corroborate the hypothesis of the intervention of grammatical constraints in word production as explored in the PWI task.

Introduction
Models of lexical access share the assumption that different kinds of linguistic information (semantic, orthographic-phonological, syntacticgrammatical, and so on) have different levels of lexical representation (Caramazza, 1997; Levelt, Roelofs and Meyer, 1999; Dell, 1986). The picture-word interference (PWI) paradigm has been widely exploited to test the dynamics of activation of different properties of words during lexical production. Such a task allows the observation of specific lexical effects by manipulating the linguistic relation between words to be used in a picture naming task and written distracterwords super-imposed to pictures. The basic assumption is that linguistic information of a distractor inﬂuences the time needed to select the appropriate word-form to name a picture. For instance, two well-known effects observed in PWI, the semantic interference and the phonological facilitation effects, are thought to reflect respectively the competition at the lexical level between the lexical representations of the target and the distracter and the co-activation of the phonemes shared by the target and the distracter during the phonetic encoding stage. Scholars have also tried to investigate the activation of grammatical information in speech production through the PWI paradigm but conflicting evidence has been collected. For instance, Pechmann and Zerbst (2002), Pechmann and coll. (2004), Vigliocco and coll. (2005), Rodriguez-Ferreiro and coll. (2014), De Simone and Collina (2016) obtained grammatical class effects, while Mahon and coll. (2007), Iwasaki and coll. (2008) and Janssen and coll. (2010) did not. Arguably, the variability in the experimental evidence can be ascribed to heterogeneous methodologies across studies: for instance, results obtained by Vigliocco and coll. (2005) could be biased by their methodological choice to administer noun-distracters with determiners, while in the study of Rodriguez-Ferreiro and coll. (2014) semantic categories (actions/objects/instruments) partially overlapped grammatical classes and a confound due to an imageability bias (Exp. 3) was present. As a consequence, the intervention of grammatical constraints during production processes, as explored in PWI tasks, is still debated. In this study on Italian we aimed at exploring the problem by trying to avoid possible confounds existing in previous studies.

Conclusion
One of the aim of the present experiment was to overcome some limitations of previous investigations. The following constraints were adopted: 1. We contrasted the production of verbs when presented with semantically related and unrelated distracters: the expected semantic interference effect guaranteed for the reliability of the paradigm. 2. We selected experimental materials where the differences between grammatical classes in terms of their semantic domain (objects (nouns) vs. actions (verbs)) was kept under control. 3. Word-class ambiguous items were excluded by experimental materials. 4. Inflected finite verbal-forms were used both as targets and distracters: these verbal forms allow to maximize the difference between nouns and verbs2. Actually, the Italian inflected form “amavo” (indicative, imperfect, 1st singular person, I used to love), is composed of a stem, “am-”, which conveys the core meaning of the verb, the vowel “-a-”, which specifies the inflectional pattern compatible with the verbal stem, the segment “–v-”, which encodes mood and tense information, and the segment ”-o” which encodes person and number information. None of these features, with the exception of meaning and number features, can be part of the lexical representation of noun-forms. This latter manipulation has relevant consequences on the detection of grammatical class effect in PWI, since it has been demonstrated that, when finite verbs have to be produced, the naming context sets the response-relevant criterion on the grammatical class of verbs and then noundistracters tend to interfere significantly more than verb-distracters (De Martino & Laudanna, 2017)3. Consistently with previous PWI evidence, our experiment replicated a reliable semantic interference effect. This finding confirms that the selection of an oral target response is slowed-down by the activation of a semantically-related distracter because the lexical system has to manage the level of activation of target lexical competitors, including the highly activated semantically related distracter word. Interestingly, we observed that, at least when pictures have to be named by using inflected verb forms, such an effect does not equally affect all semantically related target-distracter pairs: related pairs sharing grammatical class information do not exhibit significant semantic interference but grammatical-class incongruent pairs do. In conclusion, our data suggest that the PWI task is sensitive to the manipulation of grammatical class information. In other words, such a pattern of results is compatible with the intervention of grammatical constraints during production processes, as explored in the PWI task.