Colour mixing is fundamental to learning to paint. Students in visual art classes in secondary schools face problems in manipulating paint and discriminating colour. The kinds of base paints to be presented to students could be an important factor in learning about colour relationships and pigments. The purpose of this study was to determine whether Year 7 students generating colour mixes with paint using a triad of magenta, cyan and yellow were able to mix and discriminate more colours than if they used a triad of red(scarlet red), blue (ultramarine light) and yellow (lemon yellow) which is a base triad commonly used in schools. The Weddell Colour Discrimination Test was developed for use in this study which was a test that involved colour mixing with paint. The study used quasi-experimental designs for both a pilot study and a main study. Results indicated a significant difference in the ability to mix paint advantage of groups that used cyan , magenta and yellow. Implications for the use of particular colour triads in art classrooms and methods of teaching colour theory have emerged from this study. The Weddell Colour Discrimination test instrument developed in this study could be useful as both a diagnostic tool and a teaching tool as well as a data gathering method for further research.

Chez les mammifères, le néocortex constitue une structure remarquablement plastique assurant leurs multiples capacités d’adaptation et d’apprentissage. Par exemple, l’apprentissage associatif permet à chaque individu d’apprendre les relations entre un événement particulier (un danger par exemple) et les signaux environnementaux qui y sont associés, afin d’en anticiper les conséquences s’il se reproduit dans le futur. Dans le cas de la peur conditionnée, l'apprentissage associatif améliore les capacités de discrimination des signaux de menace et de sécurité, garantissant ainsi une représentation précise de l'environnement. Ce processus comportemental est en partie dépendant de l'interaction entre deux structures cérébrales: le cortex préfrontal (PFC) et le complexe basolatéral de l'amygdale (BLA). Bien que le PFC puisse encoder à la fois les mémoires de menace et de sécurité qui seraient recrutées préférentiellement après l'apprentissage, on ignore toujours si une telle représentation discriminative existe réellement, et si oui, les mécanismes neuronaux et synaptiques qui en sont à l'origine. Au cours de mon travail de thèse, j'ai démontré que l'activité des neurones excitateurs du PFC est nécessaire à la discrimination entre les signaux de menace et de sécurité grâce à la formation d'ensembles spécifiques de neurones. Au cours de l'apprentissage, les neurones pyramidaux sont potentialisés et recrutés au sein de ses ensembles grâce à l'association au niveau dendritique d'événements synaptiques non-linéaires issus des entrées sensorielles avec des entrées synaptiques provenant de la BLA. En conclusion, nos données fournissent la preuve d'un nouveau mécanisme synaptique qui associe, pendant l'apprentissage, l'expérience perçue avec l’état émotionnel transmis par la BLA permettant ainsi la formation d'ensembles neuronaux dans le cortex préfrontal. / The ability of an organism to predict forthcoming events is crucial for survival, and depends on the repeated contingency and contiguity between sensory cues and the events (i.e. danger) they must predict. The resulting learned association provides an accurate representation of the environment by increasing discriminative skills between threat and safety signals, most likely as a result of the interaction between the prefrontal cortex (PFC) and the basolateral amygdala (BLA). Although it suggests that local neuronal networks in the PFC might encode opposing memories that are preferentially selected during recall by recruiting specific cortical or subcortical structures, whether such a discriminative representation is wired within discrete prefrontal circuits during learning and by which synaptic mechanisms remain unclear. Here, the work at issue demonstrates that discrimination learning of both safe and fear-conditioned stimuli depends on full activity of the frontal association cortex, and is associated with the formation of cue-specific neuronal assemblies therein. During learning, prefrontal pyramidal neurons were potentiated through sensory-driven dendritic non-linearities supported by the activation of long-range inputs from the basolateral amygdala (BLA). Taken together, these data provide evidence for a new synaptic level mechanism that coincidently link (or meta-associate) during learning features of perceived experience with BLA mediated emotional state into prefrontal memory assemblies.

<p dir="ltr">Upon acquiring or learning another language, cross-linguistic influence (CLI) is an inevitable phenomenon with which a bilingual speaker lives. One key aspect of CLI is its bidirectionality, flowing between both the first (L1) and second languages (L2) mutually affecting each other. However, investigations of L1 CLI on L2 have dominated previous bilingual studies, and despite the increasing amount of research on L2 CLI on L1, the phonetic and phonological domains remain relatively underexplored. The primary goal of the present study is to expand our understanding of the underlying mechanisms governing L2 CLI on L1 phonetics and phonology.</p><p dir="ltr">The present study investigates L2 CLI on L1 phonetics and phonology by examining both the speech perception and production of L1 sound categories among two different groups of bilinguals, Korean heritage speakers (HSs, <i>n</i> = 30) and long-term immigrants (LTIs, <i>n</i> = 27) group participants in the US, in comparison to L1(Korean)-immersed (L1-i) native speakers residing in South Korea (<i>n</i> = 30). Participants completed a series of three experimental tasks: (1) a three-alternative forced-choice (3AFC) identification task, (2) an AX discrimination task, and (3) a controlled reading paradigm task.</p><p dir="ltr">Experiment 1 (3AFC task) was conducted to investigate the extent and direction of L2 CLI in perceptual cue weighting to L1 speech categories. In this task, participants listened to a Korean word in each trial, potentially differing in the word-initial stop, and decided which word they heard from a real-word Korean minimal triplet /pul/ ‘fire,’ /p^hul/ ‘grass,’ and /p^*ul/ ‘horn.’ Specifically, the word-initial stop consisted of an eight-by-eight orthogonal voice onset time (VOT)–onset f0 continuum, created through a speech resynthesis technique. Based on the similarities and differences in the use of the two acoustic parameters between Korean (either onset f0 or VOT is a primary cue) and English stops (VOT is the primary cue), bilingual participants were expected to exhibit different cue-weighting patterns, as compared to L1-i speakers. The results from the mixed-effects logistic regression model analyses indicated that while HSs were less sensitive to the Korean primary cue, onset f0, compared to L1-i speakers—suggesting assimilation to L2 in the perceptual domain—LTIs exhibited greater sensitivity to this cue, indicating dissimilation from L2. It was also found that bilingual participants’ Korean dominance significantly influenced their cue weighting in the perception of Korean stops.</p><p dir="ltr">Experiment 2 (AX discrimination task) was administered to assess participants’ perceptual accuracy for L1 stop categories and the potential impact of L1 cue weighting, as estimated in Experiment 1, on their discrimination performance. Notably, the VOT in the stop stimuli used in the AX task were resynthesized to have a consistent VOT of 70 ms across all stimuli. This setup created a condition where participants had no choice but to rely solely on the onset f0 cue—the primary cue to the Korean lenis-aspirated stop contrast, rendering VOT, the primary cue for the voicing contrast in English stops, uninformative. The results from mixed-effects logistic regression models showed that HSs were significantly less accurate in discriminating their L1 stop categories without the VOT cue, while LTIs outperformed the L1-i speakers. That is, the LTI group, the most balanced group in terms of language dominance, had the highest accuracy in discriminating L1 contrasts among the participant groups. Furthermore, individual sensitivity to the onset f0 cue was found to be positively correlated with discrimination performance.</p><p dir="ltr">Experiment 3 (Controlled reading paradigm) aimed to examine L2 CLI on the implementation of acoustic parameters for L1 Korean stops, as well as the potential impact of proficiency and dominance on these parameters. Participants read aloud a list of minimal triplet stimuli differing in the word-initial stop within a carrier phrase. A machine-learning-based audio signal detection system was used to analyze the acoustic parameters, and Bayesian mixed-effects linear regression models, along with quadratic polynomial regression models, were implemented for statistical analysis of the processed data. The results of the production task mirrored the perception task (Experiment 1): HSs demonstrated assimilation to L2 via onset f0, while LTIs showed dissimilation, as compared to L1-i speakers. The analysis also revealed that the degree of bilingual balance in dominance and proficiency significantly influenced the implementation of onset f0, with more balanced bilinguals exhibiting greater category contrasts than less balanced bilinguals, regardless of whether they were Korean-dominant or English-dominant.</p><p dir="ltr">The findings from these experiments provide concrete evidence of L2 CLI in L1 phonetics and phonology. Importantly, the results demonstrate that not only the timing of L2 acquisition and the quantity and quality of L2 input but also the quality and quantity of L1 acquisition and bilingual balance contribute to the direction and the degree of L2 CLI in L1 speech. These findings align with the predictions of the revised Speech Learning Model (SLM-r, Flege & Bohn, 2021) and expand its scope of application to include both HSs and LTIs. In particular, the evidence of category assimilation and dissimilation lends support to the bidirectional CLI hypothesis proposed by SLM-r. To conclude, the present dissertation expands our understanding of the nature of L2 CLI in L1 phonetics and phonology in bilingual speakers.</p>

La prise de décision est un processus computationnel fondamental dans de nombreux aspects du comportement animal. Le modèle le plus souvent rencontré dans les études portant sur la prise de décision est appelé modèle de diffusion. Depuis longtemps, il explique une grande variété de données comportementales et neurophysiologiques dans ce domaine. Cependant, un autre modèle, le modèle d’urgence, explique tout aussi bien ces mêmes données et ce de façon parcimonieuse et davantage encrée sur la théorie. Dans ce travail, nous aborderons tout d’abord les origines et le développement du modèle de diffusion et nous verrons comment il a été établi en tant que cadre de travail pour l’interprétation de la plupart des données expérimentales liées à la prise de décision. Ce faisant, nous relèveront ses points forts afin de le comparer ensuite de manière objective et rigoureuse à des modèles alternatifs. Nous réexaminerons un nombre d’assomptions implicites et explicites faites par ce modèle et nous mettrons alors l’accent sur certains de ses défauts. Cette analyse servira de cadre à notre introduction et notre discussion du modèle d’urgence. Enfin, nous présenterons une expérience dont la méthodologie permet de dissocier les deux modèles, et dont les résultats illustrent les limites empiriques et théoriques du modèle de diffusion et démontrent en revanche clairement la validité du modèle d'urgence. Nous terminerons en discutant l'apport potentiel du modèle d'urgence pour l'étude de certaines pathologies cérébrales, en mettant l'accent sur de nouvelles perspectives de recherche. / Decision‐making is a computational process of fundamental importance to many aspects of animal behavior. The prevailing model in the experimental study of decision‐making is the drift‐diffusion model, which has a long history and accounts for a broad range of behavioral and neurophysiological data. However, an alternative model – called the urgency‐gating model – has been offered which can account equally well for much of the same data in a more parsimonious and theoretically‐sound manner. In what follows, we will first trace the origins and development of the DDM, as well as give a brief overview of the manner in which it has supplied an explanatory framework for a large number of behavioral and physiological studies in the domain of decision‐making. In so doing, we will attempt to build a strong and clear case for its strengths so that it can be fairly and rigorously compared to potential alternative models. We will then re‐examine a number of the implicit and explicit theoretical assumptions made by the drift‐diffusion model, as well as highlight some of its empirical shortcomings. This analysis will serve as the contextual backdrop for our introduction and discussion of the urgency‐gating model. Finally, we present a novel experiment, the methodological design of which uniquely affords a decisive empirical dissociation of the models, the results of which illustrate the empirical and theoretical shortcomings of the drift‐diffusion model and instead offer clear support for the urgency‐gating model. We finish by discussing the potential for the urgency gating model to shed light on a number of clinical disorders, highlighting a number of future directions for research.