Gennclus: New models for general nonhierarchical clustering analysis

A general class of nonhierarchical clustering models and associated algorithms for fitting them are presented. These (metric) clustering models generalize the Shepard-Arabie Additive Clusters model in allowing for: (1). either overlapping or nonoverlapping clusters; (2). either symmetric (one-way clustering) or nonsymmetric (two-way clustering) proximities (input data); and, (3). either symmetric or diagonal weights. The GENNCLUS algorithms utilize alternating least-squares methods combining ordinary and constrained least-squares, nonlinear constrained mathematical programming, and combinatorial optimization techniques in estimating model parameters. In addition to developing the mathematical bases of these models, a comprehensive set of Monte Carlo simulations of the different models is reported. Two applications concerning brand-switching data and celebrity-brand proximities are discussed. Finally, extensions to three-way models, nonmetric analyses, and other model specifications are provided.Wayne S. DeSarbo is a Member of Technical Staff in the Mathematics and Statistics Research Center at Bell Laboratories in Murray Hill, N.J. I wish to thank R. Gnanadesikan, J. D. Carroll, and P. Arabie for their comments on a previous draft of this paper. I also wish to acknowledge the computer assistance provided by Linda Clark. Finally, I wish to thank the reviewers and editor for their very complete reviews and comments.     

The predictive efficiency of Holland's SDS summary codes in terms of career choice: A four-year follow-up

This study was designed to investigate the predictive efficiency of the primary and secondary summary codes of Holland's Self-Directed Search for Educational and Vocational Planning (SDS) in terms of expressed career choice 4 years later. In 1974, 126 voiationally undecided high school seniors were given the SDS, followed by a revision of Trow's Vocational Choice Inventory (VCI) in which they were asked to express a career choice or a state of indecision. In 1978, this same group was mailed a posttest VCI; the responses of 84 subjects were then analyzed. The subjects' expressed career choices on both the 1974 and 1978 VCI were compared to the primary and secondary summary codes on the SDS which they had taken in 1974. Inspection of the responses indicated that 21.4% of the subjects had made career choices predicted by their primary summary codes and 51.2% had made vocational choices found among their secondary summary codes. Only 27.4% chose a career area not predicted by their 1974 SDS results. The results of this study appear to lend support to the validity of using the SDS summary codes to predict eventual career decisions.     

Acknowledgement

Four experiments examined the effects of noise on semantic memory. The first was a replication of a study by Eysenck, in which subjects had to retrieve words beginning with particular letters which were also instances of specified categories (e.g. Fruit-A). Whereas Eysenck had found that both noise and activation level of the individual interacted with the dominance of the category instance possible, the present study failed to repeat the findings.The remaining experiments used a paper-and-pencil modification of Eysenck's technique; the second and third were successful in showing interactions of dominance and noise, but in opposite directions. The two experiments differed only in the previous experience of the subjects. In a fourth experiment, the same materials were presented in a different sequence, mixing dominant and non-dominant instances. The interaction then disappeared again.These experiments therefore suggest that the effect of noise on memory is not a uniform and mechanical exaggeration of dominance, but depends on the retrieval strategies being employed by the particular subject.     

Vocational maturity and anxiety among vocationally undecided and indecisive students : The effectiveness of Holland's Self-Directed Search

This study was designed with two purposes in mind: (1) to measure the effectiveness of Holland's Self-Directed Search for Educational and Vocational Planning (SDS); and (2) to test the validity of Goodstein's (Theories of Counseling. B. Stefflure, Ed., 1965) hypothesis that career indecision and indecisiveness are differentially related to anxiety and vocational maturity. A total of 66 high school males and 60 high school females were randomly assigned to experimental and control groups and tested for anxiety and vocational maturity levels; the experimental subjects were given the SDS. Statistical analysis indicated that the SDS was an effective instrument in reducing career indecision; Goodstein's hypothesis was not supported by the results of the study.     

A simple technique for correlating film and EMG in locomotion studies

Two recurring problems hampering investigations of muscular activity patterns during locomotion are electrical “noise” and movement artifact in the electromyographic (EMG) signal and proper synchronization of behavioral events to the EMG. A relatively simple technique for achieving these ends is presented. Vigorous locomotor movements of unrestrained animals are recorded on 16-mm film and synchronized with one or more EMGs from selected muscles with little electrical noise or movement artifact interference. The system employs telemetry which is compared to hardwire techniques.     

Measuring circadian cycles: A simple temperature recording preparation

While measurement of temperature as an index of circadian rhythmicity is not a difficult task with infrahuman subjects, long-term monitoring of deep body temperature with human subjects poses numerous measurement and safety problems. A preparation is described that is highly accurate, inexpensive, chronic, comfortable, and eliminates safety problems associated with more traditional methods of temperature measurement.