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Recently Burton, Bruce and Johnston (1990) have presented an interactive activation and competition model of face recognition. They have shown that this IAC model presents a parsimonious account of semantic and repetition priming effects with faces. In addition, a number of new predictions are evident from the model's structure. One such prediction is highlighted by Burton et al. themselves - that for short prime-target stimulus onset asynchronies (SOAs) a face should prime the recognition of a target name (or vice versa), 'self priming'. This thesis examined this prediction and found that it held for a design in which items were repeated across prime type conditions (same, associated, neutral and unrelated). Further, cross (face prime/name target) and within-domain (name prime/name target) designs were found to produce equivalent degrees of self and semantic priming (Experiments 1 and 2). Closer examination of the Burton et al. model suggested that the effect of domain equivalence for self priming should not hold for a design in which the stimulus items are not repeated across prime type conditions (i.e. subjects are presented with each item only once). This prediction was confirmed in Experiments 3, 4, 5 and 6.The time courses of self and semantic priming were investigated in two experiments where the interstimulus interval (ISI) between prime and target, and prime presentation times were varied. The results proved difficult to accommodate within the Burton et al. model, but it is argued that they did not provide a sufficient basis on which to reject the model. Finally, the self priming paradigm was applied to the study of distinctiveness effects. Faces judged to be distinctive in appearance were found to produce more facilitation than faces judged to be typical in appearance. Similarly, caricatured representation of faces were found to produce more facilitation than veridical or anticaricatured representations. The results of the distinctiveness studies are discussed in terms of the Valentine's (1991a; 1991b) exemplar-based coding model and Burton, Bruce and Johnston's (1990) IAC implementation. It is concluded that the results of these experiments lend support to the Burton et al. model.

Language production is ubiquitous in everyday life. A critical component of language production is the retrieval of individual words. In this thesis, we investigated the process of lexical access across six experiments that required participants to produce words in different contexts. First, we examined whether semantic relationships between proper names lead to competition during lexical access. Participants were asked to name celebrity pictures after either reading a famous or non-famous prime name or classifying a prime name as belonging to a famous or non-famous person. Results revealed that successful name retrievals decreased with increasing trial number. Within individual trials, tip-of-the-tongue states increased only after the classification of famous prime names. These findings indicate that the effects of competition from related proper names vary based on the particular semantic context in which they are retrieved. Next, we examined how the broader semantic context of sentences affects access to object names. It is widely accepted that highly constraining contexts can facilitate lexical access through predictive processing. We examined whether prediction during language processing still confers a benefit in situations where predictions were either almost correct or completely incorrect. In three experiments that investigated both language production and comprehension, we found a clear cost to incorrect predictions which we hypothesize may be used as an error signal in language learning to fine tune the language system. Finally, we investigated function word production using a task that required individuals to read aloud short paragraphs that contained errors on function words under distracting versus silent conditions. We found that background speech did not affect the likelihood that speakers would spontaneously correct the errors, but did increase non-target function word substitution errors. Overall, these studies support a framework in which lexical access is influenced by both word-class and semantic context at the point of retrieval. / Dissertation / Doctor of Philosophy (PhD) / Language plays a key role in our everyday lives, including in social interactions, academic success, and overall daily functioning. The process of producing and understanding language is deceptively easy for the average person, but there are significant outstanding questions about how linguistic processes operate. The retrieval of individual words in particular has been the subject of decades of investigation. The goal of the present thesis is to investigate how we retrieve words when we speak, or the process of lexical access, by eliciting production of words across various contexts. The studies reported here demonstrate the effects of semantic context on lexical access, as well as how this process differs for words that convey syntactic versus meaningful content (i.e., words that differ in lexical class). Our findings build on theories of lexical access by demonstrating unique effects of the roles of semantic contexts and lexical class on word retrieval.

Although a lot of information is available from our environment at every moment, only a small part gives rise to a conscious percept. It is then legitimate to wonder which mechanisms are involved in the perception phenomenon. On the basis of which processes will a sensory stimulation be perceived consciously? What happens to the stimulations that are not consciously perceived? The work presented in this thesis aims to bring some elements of response to these two questions in the auditory modality. Through different behavioral and electroencephalographic studies, we suggest that knowledge could have a top-down facilitatory influence on high-level as well as on low-level (like detection) processing of complex auditory stimulations. The stimulations we have some knowledge about (phonologic or semantic) are more easily detected than the stimulations that contain neither phonologic nor semantic information. We also show that the activation of the knowledge influences the perception of subsequent stimulations, even when the context is not perceived consciously. This is evidenced by a subliminal semantic priming effect and by modifications of the neural oscillations in the beta frequency band associated with lexical processing of stimulations that were not consciously categorized. Hence, auditory perception can be considered as the product of the continuous interaction between the context set by the environment and the knowledge one has about specific stimuli. Such an interaction would lead listeners to preferentially perceive what they already know. / Tandis que de nombreuses informations sont disponibles dans notre environnement à chaque instant, toutes ne donnent pas lieu à une perception consciente. Il est alors légitime de se demander quels mécanismes entrent en jeu dans le phénomène de perception. Sur la base de quels processus une stimulation sensorielle sera-t-elle perçue de façon consciente ? Que deviennent les stimulations qui ne sont pas perçues consciemment ? Ce présent travail de thèse vise à apporter des éléments de réponse à ces deux questions dans la modalité auditive. À travers plusieurs études utilisant des approches comportementales mais aussi électroencéphalographiques, nous suggérons que les connaissances pourraient exercer une influence top-down facilitant les hauts comme les bas niveaux de traitement (comme la détection) des stimulations auditives complexes. Les stimulations pour lesquelles nous avons des connaissances (phonologiques et sémantiques) sont mieux détectées que les stimulations ne contenant ni caractéristique phonologique ni caractéristique sémantique. Nous montrons également que l'activation des connaissances influence la perception des stimulations ultérieures, et ce, même lorsque le contexte n'est pas perçu consciemment. En effet nous avons pu mettre en évidence un effet d'amorçage sémantique subliminal et nous avons observé des modifications neuronales oscillatoires dans la bande de fréquence bêta concomitante au traitement lexical de stimulations non catégorisées consciemment. L'ensemble des perceptions auditives ne serait alors que le produit d'une interaction permanente entre le contexte environnemental et les connaissances, ce qui nous conduirait à percevoir préférentiellement ce que nous connaissons déjà.

Psychologists interested in the study of language find that people are faster at making decisions about words that are related than they are at making decisions about words that are not related – an effect called semantic priming. This phenomenon has largely only been document in laboratory settings using natural languages as contest and real words as stimuli. The current study explores the relation between the semantic priming effect and a laboratory procedure designed to give rise to performances that can be described as linguistic. Six adult participants learned to partition a collection of eight stimuli into two sets of four stimuli. Following this, the subjects showed the semantic priming effect within a set of stimuli but not across sets. These data suggest that it may be possible to study linguistic phenomenon in laboratory-based procedures allowing better control and the ability to ask very precise questions about linguistic functioning.

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There are now extensive behavioral and neuropsychological evidence to indicate that semantic information of a word can be activated without conscious awareness. However, semantic activation alone may not be sufficient for observing semantic priming effects in masked lexical decision task. In the following study, two tasks were used: lexical decision and semantic categorization. Conscious awareness of the prime was systematically manipulated by varying the duration of the prime and by varying the placement of the mask in the prime-target presentation sequence. Priming effects were observed in the semantic categorization task at prime durations of 42 milliseconds but no semantic priming was observed for the same prime duration in the lexical decision task. However, semantic priming effects began to emerge in lexical decision at the longer prime durations (55 & 69 ms) and under the least effective prime-mask presentation sequences. It is proposed that semantic activation alone is not sufficient for semantic priming effects in the lexical decision task but that central executive involvement is necessary, if only at the lowest level, for facilitatory effects to be observed. Furthermore, no such central executive involvement appears to be required for the semantic categorization task. The priming effects obtained in this task is interpreted in terms of a "decision priming" effect.

Eye movements in reading are sensitive to foveal and parafoveal word features. Whereas the influence of orthographic or phonological parafoveal information on gaze control is undisputed, there has been no reliable evidence for early parafoveal extraction of semantic information in alphabetic script. Using a novel combination of the gaze-contingent fast-priming and boundary paradigms, we demonstrate semantic preview benefit when a semantically related parafoveal word was available during the initial 125 ms of a fixation on the pre-target word (Experiments 1 and 2). When the target location was made more salient, significant parafoveal semantic priming occurred only at 80 ms (Experiment 3). Finally, with short primes only (20, 40, 60 ms) effects were not significant but numerically in the expected direction for 40 and 60 ms (Experiment 4). In all experiments, fixation durations on the target word increased with prime durations under all conditions. The evidence for extraction of semantic information from the parafoveal word favors an explanation in terms of parallel word processing in reading.

Figure assignment entails competition between object properties on opposite sides of borders. The figure is perceived on the side of the border that wins the competition. Ample evidence indicates that configural familiarity is among the competing object properties. We investigated whether priming the semantics of a familiar object suggested along one side of a border can increase its likelihood of winning the competition. To prime the semantics, we presented brief masked exposures of object names before brief masked exposures of displays where a portion of a familiar object was suggested on one side of a central border separating two equal-area, black-and-white regions. Participants reported whether the figure lay on the left or right side of the central border and were unaware of the presence of the word prime. These experimental primes named either the Same Object (SO) or a Different Object (DO) as the familiar object suggested in the display. In the DO condition, the word named an object either in the Same Category (DO-SC) or a Different Category (DO-DC) as the familiar object suggested in the display, where superordinate category was defined as natural versus artificial objects. We also used non-words as control primes. We hypothesized that, if semantic activation influences figure assignment, participants in the SO and DO-SC conditions should be more likely than participants in the DO-DC condition to perceive the figure on the side where the familiar object lies following experimental primes than control primes. We did not observe differences between experimental and control prime in any condition. However, we did obtain a Prime Context Effect, in that participants were more likely to perceive the figure on the familiar side of the border in the SO and DO-SC conditions than in the DO-DC condition. The Prime Context Effect shows that participants discerned the relationship between the masked word prime and the semantics of the familiar object suggested in the display, and this led them to change their strategy on both experimental and control trials. We also found that behavior changed over the course of the experiment: Participants in the DO-DC condition perceived the figure on the familiar side of the border more often in the second half of the experiment, on both experimental and control trials. This pattern suggests that over the course of the experiment, they learned to rely more on information from the display than from the prime, perhaps by restricting their attention to the time when the figure-ground display appeared. Participants in the DO-SC condition perceived the figure on the familiar side of the border more often on experimental trials in the second half of the experiment, whereas their performance on control trials did not differ in the first and second half. We hypothesize that participants in the DO-SC condition learned to match the superordinate semantics of the experimental prime and the display, leading to semantic priming. Taken together, these results show that (1) participants can quickly learn the relationship between experimental primes and target displays and can change their strategy accordingly, and (2) semantic activation can affect figure assignment.

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