Neural and behavioural mechanisms underlying the processing of negated meanings : Words, pictures and sentences

This thesis combines a number of methodologies and measures in order to address the processing of two types of negation (with not and un) in relation to each other and to non-negated affirmative meanings. The four investigations in this thesis target the processing of these meanings at different levels, namely the word level (Study 1) and sentence level (Studies 2–4). In two artificial language learning experiments, Study 1 focuses on the cognitive operations behind the processing of the negated meanings expressed by not and un in English. Negated and non-negated meanings are presented through artificial prefixes in order to do away with factors inherent to natural language (i.e., frequency and length). The meaning ranges associated with the negated types are manipulated and tested. The results reveal that the processing difficulty of these negation types can be modulated by the scopal ranges that they cover. This study can be taken to serve as a baseline for the future research on the processing of negated meanings that involve similar cognitive operations. Using event-related brain potentials (ERPs), Studies 2–4 target the time-course of processing negation in sentence comprehension. Affirmative, prefixally negated and sententially negated adjectives (authorized, unauthorized, not authorized) are presented in complex sentential contexts using both visual (Study 2 and Study 4) and auditory (Study 3) stimuli. The results of these investigations reveal a number of discursive factors that modulate the processing of these forms in sentence comprehension. More specifically, the results reveal that factors such as visual or auditory input, order of presentation, relevance and immediacy of the information presented all affect the processing of negated meanings in context. Overall, the findings of the studies in this thesis contribute new knowledge to a dynamic view of meaning and language processing and suggest that the processing of negated meanings, similar to many other linguistic phenomena, is not only sensitive to the properties of individual words and expressions but is also modulated by contextual factors

Brain responses to negated and affirmative meanings in the auditory modality

Negation is frequently used in natural language, yet relatively little is known about its processing. More importantly, what is known regarding the neurophysiological processing of negation is mostly based on results of studies using written stimuli (the word-by-word paradigm). While the results of these studies have suggested processing costs in connection to negation (increased negativities in brain responses), it is difficult to know how this translates into processing of spoken language. We therefore developed an auditory paradigm based on a previous visual study investigating processing of affirmatives, sentential negation (not), and prefixal negation (un-). The findings of processing costs were replicated but differed in the details. Importantly, the pattern of ERP effects suggested less effortful processing for auditorily presented negated forms (restricted to increased anterior and posterior positivities) in comparison to visually presented negated forms. We suggest that the natural flow of spoken language reduces variability in processing and therefore results in clearer ERP patterns

Processing negation in a miniature artificial language

In two miniature artificial language learning experiments, we compare the processing of narrow and broad negation, corresponding to prefixal negation (unhappy) and free-standing negation (not happy) respectively, with that of non-negation (happy). Three artificial prefixes were invented to express the three meanings above. The meaning scope expressed by the negation types was manipulated in the experiments, and the processing of the three forms was tested through a picture– word verification task. In Experiment 1, the scope expressed by prefixal negation was included in the scope expressed by free-standing negation, while in Experiment 2, there was no overlap between the two negation types and the scope of free-standing negation was limited to the intermediate range of a scale. Experiment 1 showed that narrow negation is more difficult to process than the non-negated meanings, but not as difficult as broad negation. Experiment 2 showed that when the meaning scope of broad negation was restricted to the middle range, the processing difficulty found in Experiment 1 disappeared, as it did not take longer for participants to identify the middle range compared to the ends of the scale. We show that the chunking of the negated meanings relative to one another plays a role in the processing cost of these forms

Processing sentences with sentential and prefixal negation : An event-related potential study

This study is concerned with the integration of negation in relation to two models of the processing of negation: (i) the two-step model (Lüdtke et al., 2008), according to which negation involves two representations where negation is ignored in the first representation, and (ii) the pragmatic view (Nieuwland & Kuperberg, 2008), which posits that negation can be integrated without delay if it is used in a natural context. The processing of two negated forms (not authorised and unauthorised) and an affirmative form (authorised) was studied in complex congruent and incongruent contexts. Incongruities in affirmative sentences elicited a biphasic N400–P600. In both types of negated sentences, ERP patterns associated with higher processing difficulties (anterior and central negativities) were observed. The results did not support one or the other model, suggesting that the processing of negation cannot be fully captured by either of them

ERP studies of visual and auditory processing of negated sentences

In two event-related potential studies, we investigated the processing of sentences with prefixal negation (unauthorized), sentential negation (not authorized) and no negation (authorized). We asked whether prefixal and sentential negation resulted in delayed processing. In Experiment 1, sentences such as “The White House announced that the new Obama biography was authorized/unauthorized/not authorized therefore the details in the book were correct/wrong in actual fact” were presented visually word by word and were followed by a forced binary-choice task (“Did the sentence make sense?”). The underlined words indicate the manipulations and the bold words indicate the critical words. In Experiment 2, the same sentences were presented auditorily. In both experiments, ERPs to the critical words were analyzed. The results suggest that in both experiments, the False version of non-negated sentences (authorized combined with wrong) elicited a larger N400 and P600 than the True version (authorized combined with correct). Sentences with prefixal and sentential negation in the visual experiment were related to slower processing suggesting a delay in integrating negation. However, in the auditory study, False sentences elicited increases in the P600 suggesting that both negation forms were successfully processed. The difference in processing the negated forms between the two modalities could be explained by the fact that the auditory paradigm allowed for a faster presentation and participants could thus keep the negated forms in working memory, while the visual study was, due to a slower presentation, more demanding on the working memory requiring an activation of the negated meanings as the critical words appeared