<p> Understanding the variables that maintain reinforcer effectiveness has important implications for basic research to inform applied behavior analysis. The goal of the current study was to investigate the combined effects of rate of reinforcement and variability in duration and delay of reinforcement on within-session changes in operant responding in two experiments. In each experiment, Wistar rats (<i>Rattus norvegicus</i>) lever pressed for liquid sucrose on three fixed interval (FI) schedules of reinforcement. In Experiment 1, subjects lever pressed for liquid sucrose on either a constant or a varied duration of access to reinforcement. In Experiment 2, subjects were exposed to a constant or variable delay of reinforcement. Results showed two fundamental properties of behavior undergoing habituation. First, within-session decreases in responding were steeper (greater habituation) at higher rates of reinforcement than at lower rates. Second, within-session rates of responding declined more slowly (slower habituation) when access to the reinforcer was presented in a variable versus constant manner. Because habituation occurs for both ingestive and noningestive stimuli, the present study adds to the body of literature on habituation and can inform clinical practice on the variables that sustain operant behavior through varying the delivery of the reinforcer.</p>

This thesis investigated sentence comprehension impairments in patients with dementia of the Alzheimer's-type (DAT). The first three experiments investigated the nature of the impairments using different tasks. Across tasks, patients' performance by syntactic complexity, but was poorer for sentences that had more propositions. Results are discussed in terms of a post-interpretive processing impairment in these patients. Two additional experiments investigated possible determinants of sentence comprehension impairments in DAT. One employed a dual-task paradigm to examine the effect of increasing the processing load associated with sentence comprehension. The other examined processing resource limitations in the patients tested in the first and second experiments by employing a battery of tasks designed to measure all aspects of working memory. In both experiments, evidence for processing resource limitations was seen in impaired performance on a concurrent task in dual-task conditions. Results of the fifth experiment also provided evidence that DAT patients' sentence comprehension impairments are correlated with processing resource limitations.

Thesis (Ph. D.)--University of Washington, 1988. / Vita. Includes bibliographical references.

Thesis (M.A.)--York University, 2006. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 89-93). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR19699

Thesis (Ph.D.)--Pacific Graduate School of Psychology, 1990. / Source: Dissertation Abstracts International, Volume: 51-07, Section: B, page: 3597. Chair: David Frey.

Thesis (Ph.D.)--Pacific Graduate School of Psychology, 1994. / Source: Dissertation Abstracts International, Volume: 55-09, Section: B, page: 4105. Chair: Theodore Jacob.

Thesis (Ph.D.)--Pacific Graduate School of Psychology, 2000. / Source: Dissertation Abstracts International, Volume: 61-03, Section: B, page: 1663. Adviser: William J. Froming.

Thesis (Ph.D.)--Indiana University, Dept. of Linguistics, 2007. / Source: Dissertation Abstracts International, Volume: 68-09, Section: A, page: 3830. Adviser: Robert F. Port. Title from dissertation t.p. (viewed May 1, 2008).

Thesis (Ph.D.)--Indiana University, School of Health, Physical Education, and Recreation, 2005. / Chairs: David M. Koceja; Paul R. Surburg.

Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references (leaves leaves 138-147).