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.     

Speech imagery is not always faster than visual imagery

One approach to the study of mental imagery is to examine the performance characteristics of different forms of mental imagery when used in various tasks. To demonstrate the utility of this functional approach, the use of speech and visual imagery processes in the serial mental rehearsal of common verbal sequences le.g., letters of the alphabet and familiar object arrays (objects found in familiar rooms) was examined in the present experiments. Rehearsal rates and self-reporte were consistent with the hypothesis that mental rehearsal efficiency is a function of the compatibility of characteristics of the rehearsal materials and rehearsal mode. While verbal sequences were rehearsed faster under speech than under visual imagery conditions, object arrays were rehearsed as fast under visual as under speech imagery conditions. In addition, evidence was found that covert verbal rehearsal is faster than overt verbal rehearsal under some circumstances.     

The generality of overselectivity in developmentally disabled children

A growing body of research suggests that low Mental Age (MA) autistic and retarded children show a unique stimulus control deficit, one that may cause many or most of their behavioral deficiencies. This problem, stimulus overselectivity, is evidenced when a child responds only to a restricted portion of the stimulus environment when compared with normal children. The purpose of this study was to assess whether this overselectivity is general across situations or whether it is restricted to certain stimulus/task conditions. Eight autistic children, who evidenced overselectivity on a preassessment task, and 8 normal children with similar MA levels participated. All children were trained on 3 tasks to determine if overselectivity varied as a function of different stimulus conditions. Each of the 3 tasks involved training a child to respond to (i.e., touch) a card containing a circle (S +) and to avoid a blank (S ?) card. In each case, the circle comprised a series of dots. The difference between the 3 circles (tasks) was the distance between the successive dots making up each circle. Also, in the minimal separation condition the dots were smaller in size and greater in number than in the larger separation conditions. Of concern was whether autistic children learned about the gestalt (i.e., the circle), which required attention to multiple cues, or whether children would overselect and respond to the dots. The results showed that (1) stimulus overselectivity was found not to be a generalized deficit in autistic subjects; instead, it varied as a function of the stimulus variables; and (2) the stimulus variables manipulated in this study similarly influenced the responding of both normal and autistic children. The implications of these data for a theory of overselectivity are discussed.     

Creative thinking and juvenile delinquency: a study of delinquent and nondelinquent youth on the Torrance Tests of Creative Thinking.

Using the T.T.C.T. this study examined the creative thinking of 32 delinquent and 32 nondelinquent adolescent males. The delinquent group was composed of juveniles on parole status. The nondelinquent group was composed of public school students. On the variables of IQ, age, and socioeconomic class, t-test results indicated no significant differences, except on socioeconomic class, between the groups. Analysis of variance procedures were performed to determine the possibility of an interaction between levels of intelligence and delinquent status with regard to verbal and figural creativity test scores. There were no significant main effects or interaction between IQ and adjudication status with respect to figural creativity. There was a significant main effect due to adjudication status for the dependent variable of verbal creativity scores, respectively while blocking on the intelligence variable. The results were parallel to the ANOVAS which did not specifically control for the intelligence variable between the two groups.     

The role of the church in the community based care of the chronically mentally disabled: Reclaiming an historic ministry

The perplexing circumstance of the chronically mentally disabled in the community poses both a challenging ministry and significant learning opportunity for the church. Historically the church once served as a primary resource in their community life. When care shifted to the hospital in the nineteenth century, chaplains then ministered on behalf of the church. The institutional setting later spawned the clinical training and pastoral care movement, the mental patient an essential teacher and beneficiary. With the locus of care having recently returned to the community, the church can now provide social, pastoral and spiritual resources, collaborate in deinstitutionalization with the mental health delivery system, and return to a ministry of learning with the less resourceful.The Reverend Anderson serves as Chaplain Supervisor, Connecticut Mental Health Center, Box 1842, New Haven, Connecticut 06508, and as a Lecturer in Pastoral Theology at Yale Divinity School. The author wishes to thank Dr. Donald H. Williams and Fr. Henri Nouwen for their advice and encouragement during the preparation of this article.     

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.