La presente etude propose premierement une recension des ecrits en lien avec les processus impliques dans la reconnaissance des formes et, plus specifiquement, traite du role de la position et de l'orientation dans la reconnaissance de formes en deux dimensions chez le pigeon. Subsequemment, trois experiences ayant comme objectif de determiner la valeur et l'utilisation de ces dimensions spatiales sont presentees. Ces trois experiences proposent une procedure similaire ou il y a tout d'abord une periode d'apprentissage d'une discrimination entre deux stimuli comportant des dimensions differentes et ensuite un jugement de similarite entre ces stimuli et de nouveaux stimuli presentant des transformations des dimensions spatiales utilisees. Le choix des pigeons est mesure par la frequence de reponses a ces nouveaux stimuli. La premiere experience met en conflit l'information de la position et de l'orientation des composantes dans une tache de jugement de similarite. Les resultats revelent que l'information de la position est predominante sur celle de l'orientation. La deuxieme experience contraste l'information de la position et celle de la forme geometrique et tente de determiner laquelle de ces informations detient un controle sur la similarite percue lors de modifications de ces dimensions. Les resultats demontrent que l'information de la position est egalement predominante sur la forme geometrique. La troisieme experience s'attarde a l'organisation spatiale interne des composantes en utilisant des stimuli produisant une confusion chez plusieurs especes, soit l'image miroir gauche-droite et la transposition simple des composantes de la gauche et de la droite. Les resultats attestent que non seulement les pigeons n'ont pas confondu les differentes transformations, mais que, contrairement aux recherches anterieures et en concordance avec les resultats des deux premieres experiences, ils ont porte une attention particuliere a la position de chaque composante. Finalement, la discussion generale propose certaines explications theoriques et contraste les resultats obtenus aux theories de reconnaissance existantes.

This dissertation begins with a review of competing theories of human contingency judgment, and then describes a series of four original experiments designed to systematically investigate the strengths and weaknesses of current models. Among these, Cheng's (1997) Power PC theory of human contingency judgment has risen to prominence. This theory is said to address the inadequacies of both earlier associative (Rescorla & Wagner, 1972) and computational (Jenkins & Ward, 1965) approaches. Several prior tests of the Power PC theory have returned mixed or inconclusive results (Lober & Shanks, 2000; Vallee-Tourangeau, Murphy & Drew, 1997). The four experiments presented here were designed to assess predictions of the Power PC theory which had yet to be fully empirically tested, as well as to expand our current understanding of causal reasoning. Experiment 1 results were consistent with the Power PC predictions in terms of the pattern of participants' judgments, but not with regards to the levels of those judgments. Through a replication and elaboration upon conditions from Experiment 1, Experiment 2 determined that the level of the Experiment 1 judgments was not due to a ceiling effect, as could have been argued by Power PC proponents. Experiment 3 served to investigate whether the concept of reliability could possibly explain the observed deviations from Power PC, and indeed demonstrated a significant interaction of power and reliability. Despite this finding, the conjunction of Power PC and reliability is shown to be problematic. Experiment 4 confirmed that the results from experiments 1 through 3 can be expected to hold true in negative contingency space as well. Following the empirical results, further discussion of the roles of causal power, DeltaP, and reliability raises new questions and reveals a number of viable options for future research in this area. Taken as a whole, the results from these four experiments do not support the original Power PC theory, but do provide insight toward alternatives involving both confidence and reliability, which will provide a more comprehensive account of human contingency judgment.

Attention dysfunction is a hallmark of schizophrenia, a disorder in which smoking prevalence is double that of the general population. The main interest of this dissertation was in using behavioural performance (accuracy, reaction time or RT) and brain event-related potential (ERP) measures to examine the processing of distracting events in schizophrenic patients and control subjects, and to assess the effects of acute nicotine on this processing. This was accomplished in three experiments by comparing 12 minimally-tobacco-deprived control smokers with 12 outpatient smokers, the latter being assessed under double-blind, placebo-controlled (vs. nicotine) conditions. Experiment 1 used a passive, non-task paradigm to examine the mismatch negativity (MMN) ERP component, an index of early auditory deviance detection. Patients exhibited reduced MMNs to frequency and duration deviants compared to controls, and nicotine increased patients' duration MMN to a level comparable to that seen in controls. Experiment 2 used a novel auditory-auditory distraction paradigm that embeds task-irrelevant deviant features within task-related stimuli requiring location discrimination. Deviants caused RTs to be prolonged in patients and controls. Patients' MMN did not differ from controls' but attentional switching, reflected in the P3a ERP, was attenuated in patients. Nicotine increased patients' MMN to small deviants such that it was no longer smaller than the MMN to large deviants. Experiment 3 used an auditory-visual distractor paradigm requiring participants to discriminate visual letters vs. numbers preceded by task-irrelevant auditory stimuli of standard and deviant frequencies. Reaction times were prolonged by deviants in patients and controls and the MMN of patients to small deviants was diminished. Nicotine increased the MMN to small deviants and reduced RT prolongation and the involuntary attentional switching indexed by the P3a ERP associated with large deviants. Overall, these experiments demonstrated that nicotine can reduce distractibility and can normalize aberrant neural processing of distracting events in schizophrenic patients.

Source: Dissertation Abstracts International, Volume: 29-03, Section: B, page: 1184. / Thesis (Ph.D.)--The Florida State University, 1968.

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