Semantic priming effects in Italian verbs recognition: the role of grammatical classes and semantic categories
Authors: Azzurra Mancuso, Maria De Martino, Alessandro Laudanna (Università di Salerno, 2016)
Topic: Lexical and Semantic Resources and Analysis

Abstract
The hypothesis that grammatical class information is represented in the mental lexicon and that it is activated during lexical access has generated a wide literature about the differences between nouns and verbs. However, the available evidences are discordant. In this study we tried to disentangle grammatical class effects from semantic categories effects during visual word recognition by exploiting the semantic priming paradigm.Semantically related prime-target pair were arranged. They could share (verb-verb) or not (noun-verb) grammatical class information. A third condition was included where noun primes and verb targets had both an action as a referent (delitti/uccide, crimes/he-she kills). Only prime/target pairs sharing grammatical class information showed significant semantic priming effects. Results are compatible with the hypothesis that grammatical class is an organizational criterion in the mental lexicon and it is activated during lexical access.

Introduction
Psychological and neural evidence revealed that the distinction between parts of speech, mainly nouns and verbs, occurring in all languages AUTHOR affects speaker’s performance: grammatical class is preserved in speech errors AUTHOR and nouns and verbs can be selectively disrupted in aphasic populations AUTHOR. An influential hypothesis states that the grammatical class is an organizing principle in the mental lexicon AUTHOR but the picture of empirical data is actually multifaceted and often inconsistent (AUTHOR). For the sake of conciseness, here we focus on two examples of alternative interpretations about the role of grammatical class in lexical representation and processing of words. A first position, mostly grounded on word production data (AUTHOR), is that grammatical class information, although lexically represented, is only retrieved under specific circumstances, namely in sentence or phrasal contexts (AUTHOR). However, grammatical class effects are significantly reported in word production even in tasks not requiring syntactic integration (AUTHOR). A stronger lexicalist view is held in the field of recognition and comprehension processes and conceives grammatical class as a feature of words that is automatically retrieved during lexical access. Comparisons between noun/verb homographs (condannato N (the convict) vs. condannato V (past participle, convicted), AUTHOR) and homonymic nominal and verbal forms (saliva N, spittle vs. saliva V, he/she went up, AUTHOR) revealed the possibility that separate, grammatical class-specific representations are present in the lexicon. Also in this case, different patterns of data have been described (AUTHOR). A possible reason for such a divergence relies on the fact that grammatical class effects are often not clearly distinguishable from the influence of confounding variables, i.e. the imageability of words, the number of inflectional alternatives for nominal and verbal stems, the argumental structure of nouns and verbs and so on. A challenging issue is that noun/verb distinction is not lexical in nature but relies on an object/action distinction (AUTHOR). Here we aim at verifying whether lexical access to input orthographic representations of Italian verbs can be affected by the pre-activation of grammatical class information. The semantic priming paradigm was exploited and the expected facilitation effect on target verbs elicited by semantically related primes was compared across prime/target pairs sharing or not grammatical class information, i.e., noun/verb pairs vs. verb/verb pairs. In order to disentangle the possible confound between grammatical class (nouns vs. verbs) and semantic categories which nouns and verbs belong to (objects vs. actions), two different types of noun-verb pairs were used: object nouns denoting objects (candela, candle) vs. nouns denoting actions (sberla, slap). We reasoned as follows: if grammatical class informs input orthographic representations of words, its pre-activation through primes should speed up targets recognition even in a lexical decision task where any process of syntactic integration is not involved. On the contrary, semantic priming effects are expected to equally affect prime/target pairs regardless their grammatical relation. No interaction between grammatical class and semantic relation is expected because the two variables are supposed to affect lexical selection with distinct modalities (AUTHOR).

Conclusion
Our purpose here was to clarify whether grammatical class works as an organizational criterion of word representations within the mental lexicon. In particular, we aimed at demonstrating that words from different grammatical classes tend to be processed differently by speakers not only because of their differences in terms of semantic categories they belong to (actions vs. objects) or of semantic features (imageability) but also because their lexical representations specify their role as different parts of speech. From an empirical point of view, our purpose was to verify: - whether grammatical class information is automatically activated when orthographic representations of Italian verbs are accessed; - whether grammatical class effects can be detected in tasks that do not explicitly require syntactic integration processes, that is during the processing of isolated words; - whether grammatical class effects are an epiphenomenon of the semantic categories to which nouns and verbs belong to or if they are truly grammatical in nature. We addressed the issue by exploiting the semantic priming effect, a robust and well-known effect in word recognition consisting in the advantage in lexical decision tasks exhibited by target words when preceded by semantically related primes and compared to an unrelated baseline. Our experimental design was suitable to investigate the problem for two main reasons: • it allows to pre-activate a definite linguistic feature, i.e. grammatical class (nouns vs. verbs) information and/or a semantic category (actions vs. objects), and to observe whether such a property can affect word processing; • it rules out the intervention of any confound due to syntactic integration process because it focuses on lexical access to single word representations. With that aim, we manipulated the congruency of grammatical class in different kinds of prime/target pairs. The rationale of the experiment was the following: if grammatical class informs lexical representation of words, its pre-activation through the prime should modulate the expected effects of semantic priming. In order to specifically disentangle the role of grammatical class from the influence of semantic category of referents of nouns and verbs, we observed the effect in different conditions: grammatically congruent prime/target pairs, prime/target pairs from incongruent grammatical classes but both belonging to the semantic category of actions, and prime/target pairs from incongruent grammatical classes and different semantic categories (objects for nouns and actions for verbs). Our results showed that semantic priming is effective only for prime/target pairs sharing grammatical class information; much weaker effects were detected for noun/verb pairs, regardless of the semantic category of the referents. This pattern of data seems to indicate that grammatical class informs lexical representations in the orthographic input lexicon since its pre-activation through the prime modulates the expected facilitation induced by semantically related primes. In other words, grammatical class is likely to be automatically activated during lexical access to written representation of Italian verbs and, in addition, it is effective during processing of verbal forms presented outside a sentence context. This effect seems to have a truly grammatical basis as it is not elicited by grammatically incongruent prime/target pairs. Moreover, in our experiment the congruency of grammatical class between prime and target does not interact with the semantic similarity between prime and target: this suggests that the two sources of information affect the word recognition process with distinct modalities. This pattern of data, although preliminary, adds new challenging details to the debate about lexical representation of grammatical class information and provides evidence in favor of the lexicalist models that conceive grammatical class as an intrinsic property of the lexical representation consulted during lexical access which is necessarily and automatically accessed at least during written word recognition processes.