Hierarchical clustering schemes

Techniques for partitioning objects into optimally homogeneous groups on the basis of empirical measures of similarity among those objects have received increasing attention in several different fields. This paper develops a useful correspondence between any hierarchical system of such clusters, and a particular type of distance measure. The correspondence gives rise to two methods of clustering that are computationally rapid and invariant under monotonic transformations of the data. In an explicitly defined sense, one method forms clusters that are optimally connected, while the other forms clusters that are optimally compact.I am indebted to R. N. Shepard and J. D. Carroll for many stimulating discussions about this work, and for aid in preparing this paper.     

Tactile perception of sequentially presented spatial patterns

Tactile pattern recognition was studied by presenting pairs of alphabetic shapes in rapid succession at the same anatomical location, the subject being required on each trial to identify bath of the patterns. Experimental variables were the duration of each stimulus and the time between stimuli. Three aspects of the observed interaction were (1) an increase in letter reversals for very short interstimulus intervals; (2) a greater percentage of first-response errors for short-stimulus onset intervals and a greater percentage of second-response errors for long-stimulus onset intervals; and (3) a crossover in the first- and second-response error rates in the range of 100 to 200 msec. after the onset of the first stimulus. These results are consistent with some of the temporal properties of models proposed for analogous visual tasks.     

The Effects of Participation in Decision-Making on Worker Satisfaction and Productivity: An Organizational Simulation1

Although correlational evidence of a positive relationship between participation in decision-making and satisfaction is relatively consistent, whether participation in decision-making has a causal effect on satisfaction remains unclear. The present research examined, through an organizational simulation in which high and low levels of participation in decision-making were manipulated, the causal effect of participation on satisfaction and productivity. The subjects were 128 male undergraduates randomly assigned to 32 four-person groups. Results of the experiment showed that participation in decision-making had a significant positive effect on satisfaction. In addition, the correlation between perceived influence and satisfaction was positive (r= .31). Contrary to theoretically derived predictions, participation had no impact on productivity.     

Crisis prevention and intervention training for psychiatric hospital staff

A 5-day course designed to train psychiatric hospital staff verbal and physical methods of preventing violence and injury when dealing with upset patients was taught to 89 staff from maximum and less secure wards. Compared to no-treatment controls, experimental subjects improved significantly on four tests of crisis-related tests and knowledge. Questionnaire and self-report measures from staff and patients on the training wards also indicated positive course effects. Assault frequencies decreased immediately after the course and staff injuries on experimental wards were reduced after the course relative to control wards.     

Evidence of hierarchies in cognitive maps

Previous research suggested that the apparent hierarchical organization of landmarks in an environment will influence subjects’ judgments about spatial characteristics of that environment. We extended this previous work to a natural environment that has no predetermined, well-defined hierarchical structure. Using an algorithm that generates a hierarchy of landmarks from recall protocols, we constructed hypothesized clusterings of landmarks for a set of subjects familiar with the space. Then we tested these hypothesized clusters in a series of tasks, all of which required judgments about distances in the space. The results of these tests suggest that subjects do cluster landmarks on the basis of nonspatial attributes, and that the clusters have consequences for performance in various tasks that require access to spatial information.     

Relationship between the sensation seeking scale and a biographical inventory designed to predict risk-taking behavior

One hundred and five students were administered both Zuckerman's Sensation Seeking Scale (SSS) and the Torrance-Ziller biographical inventory (BI) for measuring risk-taking tendencies. Correlations between the BI and selected subscales on the SSS were positive and significant. However, the proportion of explained variance does not suggest that the SSS and the BI are tapping the same dimension.     

Conceptual systems of open university students

The Personal Opinion Scale was applied to 237 Open University and 42 York University students. The distribution of Conceptual Systems was found to be normal in the smaller sample but Open University students comprised fewer System 1 authoritarians and more System 4 problem-solvers than do comparable samples. This may have paedagogic implications. For example it suggests any authoritarianism which may be inherent in a distance-learning approach must be combatted.     

Hemispheric differences are found in the identification,but not the detection,of low versus high spatial frequencies

The processing of sine-wave gratings presented to the left and right visual fields was examined in four experiments. Subjects were required either to detect the presence of a grating (Experiments 1 and 2) or to identify the spatial frequency of a grating (Experiments 3 and 4). Orthogonally to this, the stimuli were presented either at threshold levels of contrast (Experiments 1 and 3) or at suprathreshold levels (Experiments 2 and 4). Visual field and spatial frequency interacted when the task required identification of spatial frequency, but not when it required only stimulus detection. Regardless of contrast level (threshold, suprathreshold), high-frequency gratings were identified more readily in the right visual field (left hemisphere), whereas low-frequency gratings showed no visual field difference (Experiment 3) or were identified more readily in the left visual field (right hemisphere) (Experiment 4). Thus, hemispheric asymmetries in the processing of spatial frequencies depend on the task. These results support Sergent’s (1982) spatial frequency hypothesis, but only when the computational demands of the task exceed those required for the simple detection of the stimuli.