The blocking effect is the reduced stimulus control achieved by an unfamiliar (target) stimulus, “X”, when it is paired during conditioning with a stimulus, “A”, that already has acquired control. Blocking has been relatively difficult to accomplish with nonverbal behavior in human participants, compared with either nonverbal behaviour in animals or verbal behaviour in humans. Thus my primary research purpose was to produce blocking in the nonverbal, operant behaviour of human participants. My secondary research purpose was to achieve blocking of verbal behaviour. My third research purpose was to evaluate the relationship between verbal and nonverbal results. Four experiments were conducted with introductory psychology students pressing keys in response to coloured stimuli on a computer monitor. In Experiments 1A and 1B, the blocking procedure was applied only to the negative discriminative stimulus (S−) which was paired with a response-cost contingency. Stimulus colours employed as the preconditioned and target stimuli were counterbalanced between Experiments 1A and 1B. Statistically significant results were obtained in the first case, but not in the second. Overshadowing likely occurred in both experiments, adding to blocking effects in Experiment 1A and subtracting from blocking effects in Experiment 1B. In Experiments 2A and 2B, overshadowing was better controlled and the blocking procedure was applied to both positive (S+) and negative (S−) stimuli. The key finding was blocking in Experiment 2B, with a large, statistically significant difference in response rates during the positive target stimulus. The success of blocking in Experiment 2B likely was a consequence of the powerful point-loss contingency employed with the negative stimulus, which greatly reduced the probability of generalized high-rate responding. It appears to be the first demonstration of blocking of a positive stimulus in an operant procedure employing human participants; it supports the continuity of learning principles across species. Verbal response measures in both Experiments 2A and 2B also suggested that blocking occurred. In Experiment 2A however, nonverbal measures failed to show blocking, suggesting that in humans verbal measures may be more sensitive to blocking manipulations than are nonverbal measures.

The blocking effect is the reduced stimulus control achieved by an unfamiliar (target) stimulus, “X”, when it is paired during conditioning with a stimulus, “A”, that already has acquired control. Blocking has been relatively difficult to accomplish with nonverbal behavior in human participants, compared with either nonverbal behaviour in animals or verbal behaviour in humans. Thus my primary research purpose was to produce blocking in the nonverbal, operant behaviour of human participants. My secondary research purpose was to achieve blocking of verbal behaviour. My third research purpose was to evaluate the relationship between verbal and nonverbal results. Four experiments were conducted with introductory psychology students pressing keys in response to coloured stimuli on a computer monitor. In Experiments 1A and 1B, the blocking procedure was applied only to the negative discriminative stimulus (S−) which was paired with a response-cost contingency. Stimulus colours employed as the preconditioned and target stimuli were counterbalanced between Experiments 1A and 1B. Statistically significant results were obtained in the first case, but not in the second. Overshadowing likely occurred in both experiments, adding to blocking effects in Experiment 1A and subtracting from blocking effects in Experiment 1B. In Experiments 2A and 2B, overshadowing was better controlled and the blocking procedure was applied to both positive (S+) and negative (S−) stimuli. The key finding was blocking in Experiment 2B, with a large, statistically significant difference in response rates during the positive target stimulus. The success of blocking in Experiment 2B likely was a consequence of the powerful point-loss contingency employed with the negative stimulus, which greatly reduced the probability of generalized high-rate responding. It appears to be the first demonstration of blocking of a positive stimulus in an operant procedure employing human participants; it supports the continuity of learning principles across species. Verbal response measures in both Experiments 2A and 2B also suggested that blocking occurred. In Experiment 2A however, nonverbal measures failed to show blocking, suggesting that in humans verbal measures may be more sensitive to blocking manipulations than are nonverbal measures.

If a person witnesses an event, but later receives information that contradicts what they witnessed, their memory can be impaired. An experiment was conducted to determine whether memory impairment due to misleading post-event information can be eliminated or reduced by making it easier to discriminate between the witnessed event and the post event. In addition, the study determines whether a long versus a short delay between the introduction of post-event misinformation and the test of event memory will reduce the effect of misleading post-event information. Finally, the impact of both discrimination and delay on one particular theoretical mechanism proposed to explain memory impairment, retrieval blocking, was examined. Results indicated that, at test, retrieval blocking was alleviated both when participants could discriminate between the event and post event, and after a 48-hour delay. Two competing hypotheses are reviewed and discussed as to theoretical explanations for the misinformation effect and retrieval blocking.

No description available.

No description available.

Master of Science / Department of Computing and Information Sciences / William H. Hsu / Clustering in data mining is a process of discovering groups in a set of data such that the similarity within the group is maximized and the similarity among the groups is minimized. One way of approaching clustering is to treat it as a blocking problem of minimizing the maximum distance between any two units within the same group. This method is known as Threshold blocking. It works by applying blocking as a graph partition problem. Chameleon is a hierarchical clustering algorithm, that based on dynamic modelling measures the similarity between two clusters. In the clustering process, to merge two cluster, we check if the inter-connectivity and closeness between two clusters are high relative to the internal inter-connectivity of the clusters and closeness of items within the clusters. This way of merging of cluster using the dynamic model helps in discovery of natural and homogeneous clusters. The main goal of this project is to implement a local implementation of CHAMELEON and compare the output generated from Chameleon against Threshold blocking algorithm suggested by Higgins et al with its hybridized form and unhybridized form.

No description available.

Thesis (Ph. D.)--University of Washington, 1985. / Vita. Bibliography: leaves [180]-187.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 200-211). Available also in a digital version from Dissertation Abstracts.