Listener perceptions of stuttering across two presentation modes: a quantitative and qualitative approach

The purpose of this study was to compare participants' quantitative and qualitative judgments of various forms and frequencies of stuttering, during either audiovisual or audio-only presentation modes. A total of 64 participants voluntarily agreed to participate in the study. Each participant was randomly assigned and exposed to only one of the four conditions of varying stuttering severity levels. The assigned speech sample was presented to the participant in either the audiovisual or audio-only mode. After watching or listening to the sample, participants completed a six-item Likert scale and were asked four open-ended questions. Comments made by listeners were developed into positive and negative comments as well as sorted into five theme clusters. The data analyses revealed a number of non-significant differences across mean Likert scale ratings for the six statements and for the number of positive and negative comments between the two presentation modes. However, the results provided partial support for the notion that as the frequency of stuttering increases, listeners tend to make increasingly more negative comments about the speaker. Additionally, there were no clear differences in comments across the five theme clusters between the two presentation modes. The findings suggest that the type of presentation mode does not appear to affect listeners' perceptions of stuttering to the same extent that stuttering severity does. EDUCATIONAL OBJECTIVES: The reader will be able to: (1) describe how listeners perceive and react to various frequencies of stuttering; (2) explain how audiovisual versus audio-only samples impact listener perceptions of stuttering and (3) provide examples of the ways in which qualitative data can enhance the understanding of how listeners react to various levels of stuttering.     

An examination of procedures for determining the number of clusters in a data set

A Monte Carlo evaluation of 30 procedures for determining the number of clusters was conducted on artificial data sets which contained either 2, 3, 4, or 5 distinct nonoverlapping clusters. To provide a variety of clustering solutions, the data sets were analyzed by four hierarchical clustering methods. External criterion measures indicated excellent recovery of the true cluster structure by the methods at the correct hierarchy level. Thus, the clustering present in the data was quite strong. The simulation results for the stopping rules revealed a wide range in their ability to determine the correct number of clusters in the data. Several procedures worked fairly well, whereas others performed rather poorly. Thus, the latter group of rules would appear to have little validity, particularly for data sets containing distinct clusters. Applied researchers are urged to select one or more of the better criteria. However, users are cautioned that the performance of some of the criteria may be data dependent.The authors would like to express their appreciation to a number of individuals who provided assistance during the conduct of this research. Those who deserve recognition include Roger Blashfield, John Crawford, John Gower, James Lingoes, Wansoo Rhee, F. James Rohlf, Warren Sarle, and Tom Soon.     

Buddhism in war: A study of cause and effect from Sri Lanka

In this article, I explore two attitudes towards war present among Buddhists in contemporary Sri Lanka: support for an all‐out military victory over the Liberation Tigers of Tamil Eelam (LTTE) and support for a ceasefire followed by a negotiated settlement. After a phenomenological presentation of the two approaches, I turn to the factors that have conditioned them. I argue that canonical narrative is drawn on both to support the war and to reject it and then look at more recent colonial history to provide further data, particularly to the dynamic undergirding Buddhist support for war. In the nineteenth century, under British rule, one significant ‘other’ for Sri Lankan Buddhists was the Christian. A pattern of spirited defence developed in the face of what was seen as humiliation and betrayal at the hands of Christians. This pattern, the paper suggests, can throw light on responses in the present to the very different ‘other’, the LITE.     

Interplay Between Service Era,PTSD Symptom Expression,and Treatment Completion Among Veterans

The current veteran population has grown significantly as a result of 3 recent major conflicts: Vietnam, Persian Gulf War, and Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF). Despite a strong presence in VA PTSD specialty clinics nationwide, little is known about how these veteran cohort groups differ in PTSD symptom presentation. Additionally, it is unclear how variations in PTSD symptom presentation may in turn affect treatment adherence and completion. Understanding factors associated with treatment dropout from exposure-based therapy for PTSD is an important area of study, as individuals who drop out of treatment are likely to remain symptomatic and experience significant impairment across a number of psychosocial domains. The present study examined the relationship between service theater affiliation and pretreatment symptom expression as predictors of treatment completion in a sample of 164 veterans. Although treatment completion did not differ by service era, study data revealed statistically significant differences in initial PTSD symptom expression. Implications of the results and future directions are discussed.     

Hemispheric differences in tactile and visual recognition of braille-like stimulus patterns with static and dynamic modes of inspection

Summary Braille-like patterns were presented unilaterally to both tactual and visual modalities. The subject's task was to identify the location of three dots in a 2 × 3 six-dot pattern. Specifically, tactual versus visual presentation, dynamic versus static presentation of tactual stimuli, learning, and gender were examined in relation to cerebral hemisheric differences. Data were analyzed in terms of both the number of individual stimulus dots and the number of complete three-dot patterns correctly identified with regard to their spatial location. Although no reliable laterality differences were obtained with the tactual-static condition, owing to a significant interaction between learning and side of stimulus presentation, dot positions were reported reliably more accurately when presented in a dynamic fashion, i. e., scanned by the subject, to the right hand. For the visual modality, both correct reports of individual dot positions as well as correct reports of the entire patterns were reliably more accurate for stimulus presentations to the right visual field. Increased familiarity with the task, i. e., learning accross trials, generally increased report accuracy, particularly for static presentations to the left hand. The effect of gender was negligible. The results are dicussed in terms of their theoretical implications for differential cerebral hemispheric specializations in terms of differential processing strategies.The research reported here was supported by a Grant (A8621) from the Natural Sciences and Engineering Research Council of Canada to the second author. Offprint requests should be sent to Eugene C. Lechelt, Department of Psychology, University of Alberta, Edmonton, Alberta, Canada T6G 2E9     

Constrained k‐means on cluster proportion and distances among clusters for longitudinal data analysis

Clustering individuals by measures of similarity or dissimilarity at trajectories of changes in longitudinal data enables determination of typical patterns of development and growth. The present research proposes a new constrained k‐means method with lower bound constraints on cluster proportions and distances among clusters at focused variables and time points to fulfill various needs in clustering longitudinal data. The method assumes a large number of clusters at the onset and iteratively deletes and combines clusters according to these constraints. An additional property of the proposed constrained k‐means includes direct estimation of the unknown number of clusters. Simulation results clearly show the usefulness of the method for extracting clusters in plausible, real‐life analysis including non‐normality within clusters, and the proposed algorithm works well and convergence of the estimates is satisfactory. An actual example using Japanese longitudinal data regarding sleep habits and mental health is presented to verify the utility of the proposed constrained k‐means.     

Similarity effects in face recognition

Three experiments are described which examine the effects of similarity on face recognition using a new application of hierarchical clustering analysis (HCS). Experiments I and II employed a within-groups design where subjects attempted to recognize targets among decoys from the same and different cluster to the target. Common cluster membership accounted for 72% and 84%, respectively, of all false alarms in the two experiments. Absolute error rates were affected by the number of targets actually present in the array and the style of the instructions given to subjects but were not influenced by whether successive or simultaneous test presentation was employed. Experiment III used a between-subject design where targets were embedded in arrays composed from same or different clusters. False alarm rates were significantly higher for the same cluster condition, but hit rates were unaffected by recognition context. The significance of these findings for theories of face identification is discussed.     

An examination of indexes for determining the number of clusters in binary data sets

The problem of choosing the correct number of clusters is as old as cluster analysis itself. A number of authors have suggested various indexes to facilitate this crucial decision. One of the most extensive comparative studies of indexes was conducted by Milligan and Cooper (1985). The present piece of work pursues the same goal under different conditions. In contrast to Milligan and Cooper's work, the emphasis here is on high-dimensional empirical binary data. Binary artificial data sets are constructed to reflect features typically encountered in real-world data situations in the field of marketing research. The simulation includes 162 binary data sets that are clustered by two different algorithms and lead to recommendations on the number of clusters for each index under consideration. Index results are evaluated and their performance is compared and analyzed.Author names are listed in alphabetical order.This piece of research was supported by the Austrian Science Foundation (FWF) under grant SFB#010 (Adaptive Information Systems and Modeling in Economics and Management Science).The authors would like to thank the anonymous reviewers and especially the associate editor for their helpful comments and suggestions.     

Input restriction and immediate memory decay in normal and subnormal children

Twelve imbeciles and 12 normals, matched for their digit memory span, were presented with three digit numbers successively and simultaneously. Seven speeds of presentation were used. Each simultaneous speed of presentation had a corresponding successive speed. Subjects were required to recall digits on the conclusion of presentation of each number. Each performance was scored as the number of errors for each digit. With simultaneous presentations the difference between the groups was significant only at fast presentation speed, where the normals were significantly better than the imbeciles. Imbeciles improved at slow speeds and became as good as normals. In the case of successive presentations differences between groups occur only in relation to the second digit, which the normals remember better than the subnormals. Both groups remember the first digit worst as rates of presentation become progressively slower. Results are explained in terms of input restriction and of memory trace decay.     

Are Young Adults' Suicides Psychologically Different from Those of Other Adults? (The Shneidman Lecture)

ABSTRACT: This Shneidman Lecture addresses the question: Are young adults' suicides psychologically different from those of other adults? Eight clusters (or patterns) as possible predictors of suicide notes and, by implication, suicide are discussed to address this question. The eight clusters are as follows: unbearable psychological pain, interpersonal relations, rejection-aggression, inability to adjust, indirect expressions, identification-egression, ego, and cognitive constriction. Comparisons between young adults (aged 18–25) and other adults indicate that young adults' suicides do differ psychologically in a number of patterns, but that considerable commonalities exist across the adult life span. The presentation emphasizes that a life span developmental perspective is essential when one is attempting to understand the suicides of young adults. A number of genuine suicide notes of young adults are presented to illustrate, from an idiographic view, what it might have been like for these individuals in the last moments of their lives.     

Adaptive Anchoring Model: How Static and Dynamic Presentations of Time Series Influence Judgments and Predictions

When attempting to predict future events, people commonly rely on historical data. One psychological characteristic of judgmental forecasting of time series, established by research, is that when people make forecasts from series, they tend to underestimate future values for upward trends and overestimate them for downward ones, so‐called trend‐damping (modeled by anchoring on, and insufficient adjustment from, the average of recent time series values). Events in a time series can be experienced sequentially (dynamic mode), or they can also be retrospectively viewed simultaneously (static mode), not experienced individually in real time. In one experiment, we studied the influence of presentation mode (dynamic and static) on two sorts of judgment: (a) predictions of the next event (forecast) and (b) estimation of the average value of all the events in the presented series (average estimation). Participants' responses in dynamic mode were anchored on more recent events than in static mode for all types of judgment but with different consequences; hence, dynamic presentation improved prediction accuracy, but not estimation. These results are not anticipated by existing theoretical accounts; we develop and present an agent‐based model—the adaptive anchoring model (ADAM)—to account for the difference between processing sequences of dynamically and statically presented stimuli (visually presented data). ADAM captures how variation in presentation mode produces variation in responses (and the accuracy of these responses) in both forecasting and judgment tasks. ADAM's model predictions for the forecasting and judgment tasks fit better with the response data than a linear‐regression time series model. Moreover, ADAM outperformed autoregressive‐integrated‐moving‐average (ARIMA) and exponential‐smoothing models, while neither of these models accounts for people's responses on the average estimation task.     

Interlimb differences in visuomotor and dynamic adaptation during targeted reaching in children

While a number of studies have focused on movement (a)symmetries between the arms in adults, less is known about movement asymmetries in typically developing children. The goal of this study was to examine interlimb differences in children when adapting to novel visuomotor and dynamic conditions while performing a center-out reaching task. We tested 13 right-handed children aged 9–11 years old. Prior to movement, one of eight targets arranged radially around the start position was randomly displayed. Movements were made either with the right (dominant) arm or the left (nondominant) arm. The children participated in two experiments separated by at least one week. In one experiment, subjects were exposed to a rotated visual display (30° about the start circle); and in the other, a 1 kg mass (attached eccentrically to the forearm axis). Each experiment consisted of three blocks: pre-exposure, exposure and post-exposure. Three measures of task performance were calculated from hand trajectory data: hand-path deviation from the straight target line, direction error at peak velocity and final position error. Results showed that during visuomotor adaptation, no interlimb differences were observed for any of the three measures. During dynamic adaptation, however, a significant difference between the arms was observed at the first cycle during dynamic adaptation. With regard to the aftereffects observed during the post-exposure block, direction error data indicate considerably large aftereffects for both arms during visuomotor adaptation; and there was a significant difference between the arms, resulting in substantially larger aftereffects for the right arm. Similarly, dynamic adaptation results also showed a significant difference between the arms; and post hoc analyses indicated that aftereffects were present only for the right arm. Collectively, these findings indicate that the dominant arm advantage for developing an internal model associated with a novel visuomotor or dynamic transform, as previously shown in young adults, may already be apparent at 9 to 11-year old children.     

Spatial congruency between stimulus presentation and response key arrangements in arithmetic fact retrieval

It is known that number and space representations are connected to one another in numerical and arithmetic abilities. Numbers are represented using the metaphor of a mental number line, oriented along horizontal and vertical space. This number line also seems to be linked to mental arithmetic, which is based partly on arithmetic fact retrieval. It seems that number representation and mental arithmetic are linked together. The present study tested the effect of spatial contextual congruency between stimulus presentation and response key arrangements in arithmetic fact retrieval, using number-matching and addition verification tasks. For both tasks in Experiment 1, a contextual congruency effect was present horizontally (i.e., horizontal presentation of stimuli and horizontal response key alignments) but not vertically (i.e., vertical presentation of stimuli but horizontal response key alignments). In Experiment 2, both tasks showed a contextual congruency effect for both spatial conditions. Experiment 1 showed that the interference and distance effects were found in the horizontal condition, probably because of the spatial congruency between stimulus presentation and response key arrangements. This spatial congruency could be related to the activation of the horizontal number line. Experiment 2 showed similar interference and distance effects for both spatial conditions, suggesting that the congruency between stimulus presentation and response alignment could facilitate the retrieval of arithmetic facts. This facilitation could be related to the activation of both horizontal and vertical number lines. The results are discussed in light of the possible role of a mental number line in arithmetic fact retrieval.     

Recording and analyzing eye-position data using a microcomputer workstation

This paper presents a PC-based eye-position data collection and analysis system. Software routines are described that supplement hardware calibration procedures, improving data-collection accuracy and reducing the number of unusable trials. Collected eye-position data can be remapped over a displayed stimulus image and spatially and temporally represented by parameters such as individual fixations, clusters of fixations (Nodine, Carmody, & Kundel, 1978), cumulative clusters, and gaze durations. An important feature of the system is that the software routines preserve scan-path information that provides a sequential dimension to the analysis of eye-position data. A “hotspot” analysis is also described, which cumulates, across 1 or more observers, the frequency of eye-position landings or “hits” on designated areas of interest for a given stimulus. Experimental applications in the fields of radiology, psychology, and art are provided, illustrating how eye-position data can be interpreted both in signal detection and in information-processing frameworks using the present methods of analysis.     

Gestural overlap in consonant clusters: effects on the fluent speech of stuttering and non-stuttering subjects

This study was designed to investigate if persons who stutter differ from persons who do not stutter in the coproduction of different types of consonant clusters, as measured in the number of dysfluencies and incorrect speech productions, in speech reaction times and in word durations. Based on the Gestural Phonology Model of Browman and Goldstein, two types of consonant clusters were formed: homorganic and heterorganic clusters, both intra-syllabic (CVCC) and inter-syllabic (CVC#CVC). Overall, the results indicated that homorganic clusters elicited more incorrect speech productions and longer reaction times than the heterorganic clusters, but there was no difference between the homorganic and the heterorganic clusters in the word duration data. Persons who stutter showed a higher percentage dysfluencies and a higher percentage incorrect speech productions than PWNS but there were no main group effects in reaction times and word durations. However, there was a significant three-way interaction effect between group, cluster type and cluster place: homorganic clusters elicited longer reaction times than heterorganic clusters, but only in the inter-syllabic condition and only for persons who stutter. These results suggest that the production of two consonants with the same place of articulation across a syllable boundary puts higher demands on motor planning and/or initiation than producing the same cluster at the end of a syllable, in particular for PWS. The findings are discussed in light of current theories on speech motor control in stuttering. EDUCATIONAL OBJECTIVES: The reader will be able to describe: (1) the effect of gestural overlap between consonant clusters on speech reaction time and word duration of people who do and do not stutter and be able to (2) identify the literature in the field of gestural overlap between consonant clusters.     

Semantic and syntactic factors in the perception of rapidly presented sentences

An important controversy in psycholinguistics has been the nature of the initial hypothesis in sentence processing. This problem has been directly addressed with the Rapid Serial Visual Presentation (RSVP) technique, in which words of a sentence are presented one at a time at tachistoscopic rates. The results of this research (Forster and Ryder, 1971) have provided evidence against Bever's (1970) thesis that most normal perceptual processing of sentences is probably carried out with little regard to actual sequence or structure. However, since the number of words seen is a result of presentation speed as well as psycholinguistic processing, this result could be an artifact of presentation rate. A slower or faster rate could facilitate different processing strategies and perhaps suggest a different nature of the initial hypothesis. Thus, the present study is a conceptual replication of Forster and Ryder (1971), at different presentation rates. While significant effects for syntactic structure were obtained only at the slower presentation rate, results for semantics were significant at both slow and fast presentation speeds. Thus, insofar as sentence perception with the RSVP technique reflects the nature of the initial hypothesis, it is suggested that the hypothesis is semantic.     

An algorithm for generating artificial test clusters

An algorithm for generating artificial data sets which contain distinct nonoverlapping clusters is presented. The algorithm is useful for generating test data sets for Monte Carlo validation research conducted on clustering methods or statistics. The algorithm generates data sets which contain either 1, 2, 3, 4, or 5 clusters. By default, the data are embedded in either a 4, 6, or 8 dimensional space. Three different patterns for assigning the points to the clusters are provided. One pattern assigns the points equally to the clusters while the remaining two schemes produce clusters of unequal sizes. Finally, a number of methods for introducing error in the data have been incorporated in the algorithm.     

A Graph Theoretic Criterion for Determining the Number of Clusters in a Data Set

This article is concerned with procedures for determining the number of clusters in a data set. Most of the procedures or stopping rules currently in use involve finding internally coherent and externally isolated clusters, but do not derive from the formal structure of the respective clustering model. Based on the graph theoretic concepts of minimal spanning tree, maximal spanning tree, and homomorphic function, a new criterion is advanced that yields a well-defined clustering solution. Its performance in determining the number of clusters in several empirical data sets is evaluated by comparing it to four prominent stopping rules. It is shown that the proposed criterion not only possesses mathematically attractive properties but also may contribute to solving the number-of-clusters problem.     

Identification of fragmented object outlines: A dynamic interplay between different component processes

The speed of fragmented picture identification depends on a large number of factors whose effects might change in time during an identification attempt. Using survival analysis and fixed fragmentation levels, previous research has shown that effects of complexity, fragment curvature, and time interact. Here, we study the effects of presentation duration and dynamic fragmentation levels. Fragmented object outlines were presented repetitively every 2.25 s, and at each presentation longer fragments were shown (possibly until closure). We recorded the lowest presentation number (minimum 1, maximum 10) that resulted in correct naming by the participants (N=84). Survival analysis was employed to investigate whether and when different factors like presentation duration, complexity, object category (natural vs. artifactual), symmetry, proximity, and fragment curvature influence correct identification. The results confirm and extend previous findings, and are interpreted within a dynamic, interactive processing framework.     

Software for the generation and display of random-dot cinematograms on the Macintosh computer

The software packageDotMovie 1.3.8 was designed to create and display dynamic random-dot cinematograms for studies of motion perception on Macintosh II microcomputers. In each frame of the cinematogram, some dots move in random uncorrelated directions, while other dots move with constant speed in one direction. As the relative number of dots moving in a correlated direction increases, the observer sees flow in the direction of the movement. The software described facilitates the creation of random-dot cinematograms, their presentation, and collection of data from subjects’ responses.