This thesis concerns selective attention in the context of the Stroop task (identify the colour) and Reverse Stroop task (identify the word). When a person is asked to select and identify one dimension of a bidimensional stimulus (e. g. , the word RED printed in green) the typical finding is that the word influences colour identification (i. e. , the Stroop effect) but the colour does not influence word identification (i. e. , no Reverse Stroop effect). A major account of performance in these tasks posits that one dimension interferes with the other only when a translation occurs (e. g. , Roelofs, <i>Psychological Review, 2003</i>; Sugg & McDonald, <i>Journal of Experimental Psychology: Human Perception & Performance, 1994</i>; Virzi & Egeth, <i>Memory & Cognition, 1985</i>). This translation assumption is implicit in virtually all work in the field. The first part of this thesis completely undermines the translation assumption. In a series of four experiments (two unique paradigms), I demonstrate that interference from the colour in a Reverse Stroop task occurs in the absence of a translation. The second part of this thesis contains two additional experiments designed to discriminate between translation effects and response conflict effects. The results of these experiments confirm that a translation was not required because no stimulus conflict effect, the most likely locus of a translation effect, was observed. However, response conflict effects were observed. The third part of this thesis implements a computational model based on the principle that the strength of association (Cohen, Dunbar, & McClelland, <i>Psychological Review, 1990</i>) between a specific stimulus and its response (Logan, </i>Psychological Review, 1988</i>) is important in determining the influence of the irrelevant dimension. This model has no translation mechanism. A final experiment was conducted to test this model; the model accounted for over 98% of the variance in RTs and 92% of the variance in interference and facilitation scores in both the Stroop and Reverse Stroop tasks independent of whether a translation was required.

An Information Theoretic approach is used for studying the effect of noise on various spiking neural systems. Detailed statistical analyses of neural behaviour under the influence of stochasticity are carried out and their results related to other work and also biological neural networks. The neurocomputational capabilities of the neural systems under study are put on an absolute scale. This approach was also used in order to develop an optimisation framework. A proof-of-concept algorithm is designed, based on information theory and the coding fraction, which optimises noise through maximising information throughput. The algorithm is applied with success to a single neuron and then generalised to an entire neural population with various structural characteristics (feedforward, lateral, recurrent connections). It is shown that there are certain positive and persistent phenomena due to noise in spiking neural networks and that these phenomena can be observed even under simplified conditions and therefore exploited. The transition is made from detailed and computationally expensive tools to efficient approximations. These phenomena are shown to be persistent and exploitable under a variety of circumstances. The results of this work provide evidence that noise can be optimised online in both single neurons and neural populations of varying structures.

The present study compared the effects of an errorless stimulus shaping procedure to an errorful fluency based procedure for teaching difficult letter sound discriminations using a counterbalanced multielement experimental design. For 2 participants, letters fsteai were taught using the errorless procedure and letters bpdvou were taught using the errorful procedure. For the other 2 participants the conditions were reversed. All participants had considerably fewer errors and fewer trials to criterion with the errorless than with the errorful procedure. Tests of retention and generalization indicate that the errorful procedure generalized and was retained at a higher frequency than the errorless procedure. For 3 participants preference for the errorless procedure over the errorful procedure was demonstrated; whereas, the fourth participant demonstrated preference for the errorful procedure.

L’hypothèse neurodéveloppementale de la schizophrénie suggère, entre autres, que l’inflammation prénatale sensibilise le cerveau en développement à une atteinte subséquente durant le jeune âge, augmentant le risque de développer la maladie. Pour mieux comprendre la pathophysiologie de la maladie, nous avons développé un modèle à double atteinte basé sur l’activation immunitaire gestationnelle au polyIC (PIC) suivie d’un stress de contention à l’âge juvénile chez la souris. Un effet additif est observé sur le déficit de l’inhibition du réflexe de sursaut par stimulus sonore (IPP), accompagné d’anomalies oxydatives, dopaminergiques et GABAergiques dans le cortex préfrontal (PFC) et le striatum, chez les souris exposées aux deux atteintes dès l’âge juvénile. À notre connaissance, il s’agit du premier modèle à double atteinte démontrant un déficit de l’IPP dès l’âge pubertaire. De plus, l’acide lipoïque, un antioxydant, prévient les déficits d’IPP et les anomalies neurochimiques du PFC, supportant ainsi l’implication du stress oxydatif dans la schizophrénie et suggérant que les déficits d’IPP sont associés à des anomalies du PFC. Ce modèle aidera à étudier de nouvelles alternatives thérapeutiques pour le traitement de la schizophénie, spécialement durant la phase prodromale. Sur un autre ordre d’idée, un taux élevé de mortalité par suicide existe chez les patients schizophrènes et les mécanismes pathophysiologiques de ce phénomène demeurent peu compris. Un deuxième modèle à double atteinte a été développé, présentant des comportements associés au risque suicidaire (agressivité, impulsivité, anxiété et perte d’espoir), via le polyIC prénatal suivi de l’isolement social dès le sevrage des souriceaux. Les deux atteintes interagissent pour induire plusieurs comportements de type schizophrénique et associés au risque suicidaire chez les mâles. Le chlorure de lithium, connu pour ses effets de « prévention du suicide » dans la population générale, améliore les composantes comportementales chez les animaux isolés seulement, alors que la clozapine, l’antipsychotique avec le meilleur effet de « prévention du suicide », prévient les anomalies comportementales principalement dans le modèle à double atteinte. Les effets distincts des deux molécules suggèrent que les souris exposées aux deux atteintes modélisent un phénotype distinct de celui des souris seulement isolées. Comme le diagnostic du risque suicidaire chez les patients schizophrènes demeure un défi pour les psychiatres, notre modèle in vivo aidera à mieux comprendre les mécanismes impliqués dans le comportement suicidaire chez ces patients, favorisant ainsi le développement de nouveaux traitements pour cette population vulnérable.

The experimenter asked if documented equivalence class membership would influence the development of shared discriminative stimulus function established through simple successive discrimination training. In Experiment 1, equivalence classes were established with two sets of 9 stimuli. Common stimulus functions were then trained within or across the equivalence classes. Greater acquisition rates of the simple discriminations with stimuli drawn from within the equivalence classes were observed. In Experiment 2, a third stimulus set was added with which no equivalence relations were explicitly trained. The findings of Experiment 1 were replicated, but the Set 3 results were inconsistent across subjects. The outcomes of the two experiments demonstrate that equivalence classes have an effect on other behavioral relations which requires further investigation.

The present study sought to investigate the combined influences of degree of first-list learning, stimulus order, emphasis, and meaningfulness on the selection strategies of college subjects.

The current study assessed the effects of two teaching stimulus presentations, i.e. picture to word and word to word, used to teach second language vocabulary to college students. It also evaluated the emergence of untaught relations when picture to word and word to word were used separately as a teaching strategy. The findings showed picture to word training resulted in more untaught relations. Several aspects such time allotted for online quizzes, experimental and teaching arrangements and vocabulary complexity were suggested for future research.

This study tested effectiveness of a film in forced compliance situations on neutral and negatively predisposed individuals. Subjects (N = 48) were administered an attitudinal questionnaire, subjected to a no (control), low, moderate, or high dissonance-producing situation, and retested for attitude change. Analysis of variance for repeated measures, Scheffe's F tests, and t tests were used for analysis. Results indicated attitude change was greatest under a low dissonance-producing situation for all subjects. The moderate-dissonance situation moved unfavorable subjects toward favorability while the high dissonance situation moved extremely unfavorable subjects toward favorability. No relationship was found between degrees of dissonance and attitude change for netural subjects.

The present study examined the effect of first-list stimulus context (color versus no color) and two degrees of first-list learning (twenty trials versus five trials) on cue selection and transfer of training. College students learned two paired-associate lists consisting of highly similar trigrams as the stimulus terms and nouns as the response terms. The second list consisted of twelve items presented on homogeneous white backgrounds for eighteen trials. Four secondlist items represented each of three transfer paradigms--A -B,A-B; A-B,A-C; and A-BC-D. It was concluded that color context draws attention to the color-backed items during the early stages of learning but is not selected for encoding until the later stages of learning.

A procedure in which the S- was prevented from being responded to, by electro-magnets, was used to establish color discriminations. The procedure was modified in Situation 1, to include the prevention of responses to the S+ if the S- was responded to first. The original procedure and modified procedure were used in Situation 1, with only the modified procedure being used in Situations 2 and 3. The procedure of reinforcing responses to the S+ and extinguishing responses to the S-, through nonreinforcement, was used in Situation 4. Data recorded consisted of the number of trials, the number of reinforcements, and which stimulus was first responded to. Criteria for the acquisition of a discrimination was 100 first responses to the S+. Results indicated that the modified procedure was much more effective in establishing the discriminations, than the original procedure or the procedure of reinforcing responses to the S+ and extinguishing responses to the S-. The modified procedure enhanced the establishment of stimulus control, reduced the number of errors and eliminated stereotyped responses.