Thesis--Wisconsin. / Includes bibliographical references (leaves 32-39).

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 52-54).

Thesis (M.A.)--Ball State University, 2008. / Title from PDF t.p. (viewed on Sept. 08, 2009). Includes bibliographical references (p. 17-19).

Thesis (M.S.E.)--University of Washington, 1992. / Includes bibliographical references (leaves [72]-74). Issued also electronically via World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 161-167).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 119-124).

Thesis (M.A.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.)--York University, 2009. Graduate Programme in Psychology. / Typescript. Includes bibliographical references (leaves 204-226). 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:NR51673

The psychophysical experiments and numerical modelling reported in the present study are an investigation into the encoding of relative location of intensity changes in the human visual system. The study attempted, successfully, to explain some geometric illusions resulting from closely spaced image features ('crowding'), and determined the nature of information necessary for making judgments about the separation of intensity changes for different stimulus configurations. Experiments performed fell into two basic categories; those concerned with spatial interference, and studies of spatial interval judgments. The first set of experiments, studying spatial interference with relative localisation for intensity changes, was based on measurements made with stimuli composed of lowpass filtered bars and edges. The most successful model, which accounted for all of the data, was Watt and Morgan's (1984, 1985) MIRAGE; the results suggest that a good explanation of some geometric illusions can be derived using the principles of low-level vision. Spatial interference is strong evidence for combination of information across spatial scales, and the MIRAGE algorithm makes some highly accurate predictions. Relating the separation of image features is a fundamental task for the visual system, but there is no clear understanding of what information the system has available to perform this task. The second set of experiments explored the perception of separation, and precision of judgments of separation, for bars with a variety of orthoaxial contrast profiles. The data indicate that information is combined across spatial scales (as in MIRAGE) under certain circumstances in making separation judgments; this combination of information across scale occurs when the information on the scales combined is in agreement (ie. all scales have some task-related information), but when variance is added on coarser scales which is not relevant to the task, the system is capable of selecting the finest scales of filters available, and using only the information in the finest scale. This adaptive scale-selection process operates even at very brief exposure durations.

The present series of experiments examined pigeons' spatial working memory using two variants of the delayed matching of key location paradigm (Wilkie & Summer, 1982). Exposure to the sample location was extended to 15 min and pecks to this stimulus (S+) produced grain on a variable interval 30-s schedule (the 1 Cue group). For some subjects (the 2 Cues group) both the positive and negative (S-) stimuli were presented during the sample period. In a subsequent test phase subjects were exposed to both the S+ and S- for 1 min. If the subject made more responses to the S+ an additional 15 min of access to the S+ occurred, with grain available on the previous schedule. If more responses were made to the S- the trial terminated and the subject was immediately removed from the apparatus. In the first experiment all subjects performed well with retention intervals of up to 30 s, a level of performance better than previously demonstrated in the delayed matching of key location (Wilkie & Summers, 1982). However, subjects' performance was disrupted when they were removed from the apparatus during the retention interval. Subjects in the 1 Cue group were more severely disrupted than the subjects in the 2 Cues group. Performance improved dramatically when these subjects were subsequently trained and tested on the 2 cues condition. Experiment 2 examined the differences between the 1 cue and 2 cues tasks further. All subjects were run for 30 trials on each task and removed from the apparatus during the retention interval. Performance on the 2 cues task was significantly higher for all subjects. When subjects were switched to the 1 cue task, performance immediately dropped and remained at a low level for all blocks tested. The observed differences probably reflect the operation of transfer appropriate processing (cf. Morris, Bransford, & Franks, 1977), given the similarity between training and testing on the 2 cues task. Experiment 3 used the 2 cues task to examine the performance of pigeons when retention intervals longer than 30 s were imposed between training and testing. The retention interval was incremented in the following stages: 5 min, 15 min, 30 min, 1 hr, 2 hr, 4 hr, 8 hr, 12 hr and 24 hr. Subjects were run until their performance fell below a criterion (70% accuracy or better for a block of 10 trials). When a subject failed to attain criterion within 3 blocks, no further data were collected from that subject. Subjects' upper retention limit varied somewhat, ranging from a minimum of 30 min to a maximum of 24 hr, but the performance of most subjects began to deteriorate at about 4 hr, a level considerably above the upper limit previously demonstrated in other paradigms (30 min-Spetch & Honig, 1988). Experiment 4 was a systematic replication of Experiment 3, using a mixed, rather than an incremental, schedule of retention intervals. Performance was not quite as good. For most subjects performance began to deteriorate at about 2 hr, somewhat sooner than in Experiment 3, but nevertheless higher than the level of performance seen in other paradigms. The results of the present experiments are interpreted in terms of the ecological validity of the procedures employed. The implications of the present studies for the study of "adaptive specializations in cognition" (Sherry, 1984; Sherry & Schacter, 1987), are also discussed, as are the implications for the distinction between reference and working memory. / Arts, Faculty of / Psychology, Department of / Graduate