Evaluating statistical difference, equivalence, and indeterminacy using inferential confidence intervals: an integrated alternative method of conducting null hypothesis statistical tests.

Null hypothesis statistical testing (NHST) has been debated extensively but always successfully defended. The technical merits of NHST are not disputed in this article. The widespread misuse of NHST has created a human factors problem that this article intends to ameliorate. This article describes an integrated, alternative inferential confidence interval approach to testing for statistical difference, equivalence, and indeterminacy that is algebraically equivalent to standard NHST procedures and therefore exacts the same evidential standard. The combined numeric and graphic tests of statistical difference, equivalence, and indeterminacy are designed to avoid common interpretive problems associated with NHST procedures. Multiple comparisons, power, sample size, test reliability, effect size, and cause-effect ratio are discussed. A section on the proper interpretation of confidence intervals is followed by a decision rule summary and caveats.

Modal attention asymmetry in patients with schizophrenia and bipolar disorder.

This cross-sectional study examined modal attention asymmetries in patients with schizophrenia (n = 47) and bipolar disorder (n = 42), as contrasted to a matched-sample comparison group of normal participants (n = 89). A test of continuous auditory and visual attention was the primary measure. The data were analyzed from 2 experimental conditions: simple modal responses (auditory and visual) and modal switching responses (ipsimodal and cross-modal switching). In the simple modal condition, patients with schizophrenia demonstrated a visual over auditory asymmetry; patients with bipolar disorder showed no differences. In modal switching conditions, however, patients with bipolar disorder displayed a significant auditory over visual asymmetry. No main effect was detected between medications and attention functioning. Results are discussed in light of differentiating these 2 populations on the basis of modal specificity of attention functioning.

How accurately does wrist actigraphy identify the states of sleep and wakefulness?

STUDY OBJECTIVES: Because sleep and wakefulness differ from each other by the amount of body movement, it has been claimed that the two states can be accurately distinguished by wrist actigraphy. Our objective was to test this claim in lengthy polysomnographic (psg) and actigraphic (acf) samples that included night and day components. DESIGN: Fourteen healthy young (21-35 years) and old (70-72 years) men and women lived in a laboratory without temporal cues for 7 days. Each subject continuously wore sleep-recording electrodes as well as 2 wrist-movement recorders. Act measurements were converted to predictions of sleep and wakefulness by simple-threshold and multiple-regression methods. Psg served as the gold standard for calculation of predictive values (PV, the probability that an act prediction is correct by psg criteria). SETTING: N/A. PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The 7-day act recordings showed clear circadian cycles of high and low activity that respectively corresponded to subjective days, when subjects were wakeful, and subjective nights when they slept. Lower act levels corresponded to deeper states of psg sleep. Logistic regression on a 20-minute moving average of act gave the highest overall PV's. Nevertheless, the mean PV for sleep (PVS) was only 62.2% in complete, day + night samples. PVS was 86.6% in night samples. Act successfully predicted wakefulness during subjective nights (PVW = 89.6) and accurately measured circadian period length and the extent of sleep-wake consolidation, but it overestimated sleep rate and sleep efficiency. Act systematically decreased before sleep onset and increased before awakening, but reliable transitions among joint psg/act states (the Markov-1 property) were not demonstrated. CONCLUSIONS: Low PV's and overestimation of sleep currently disqualify actigraphy as an accurate sleep-wake indicator. Actigraphy may, however, by useful for measuring circadian period and sleep-wake consolidation and has face validity as a measure of rest/activity.

Validating a double-press method for computer administration of personality inventory items.

This study describes a double-press method for experimentally controlling item length and reading speed when measuring response latency to computer-administered personality items. Previous research has required several statistical transformations to control for item length and reading speed. Five approaches validated the new, double-press method. First, valid profiles showing reasonable read time and psychological response time resulted in few outliers. Second, read and psychological response times were internally consistent. Third, valid separation of read time from total response time was demonstrated by a positive relationship between read time and item length. Fourth, negatively stated items took longer to understand than positively stated items. Fifth, in accordance with schema research, items that were highly similar or dissimilar to the self-schema were answered more quickly than other items, resulting in an inverted-U effect.

Monitoring and assessing symptoms of chronic fatigue syndrome: use of time series regression.

Chronic Fatigue Syndrome's principal symptoms are severe and include prolonged fatigue and a number of other minor symptoms. Behavioral data collection methods were used in a case study to show some of the benefits that can be derived from monitoring symptoms hourly and daily. Using time series regression, several statistically significant correlates of fatigue were found both within days and between days. Perceived energy, physical exertion, and mental exertion were significantly related to fatigue in both analyses. Collection of such data may help resolve a number of theoretical and methodological problems in research on the Chronic Fatigue Syndrome.

A bidirectional associative memory explanation of posttraumatic stress disorder.

Network theory is a relatively recent explanatory development to improve our understanding of emotions and emotional disorders. Connectionist neural networks are introduced as mathematically well-defined network theories that have been suggested as PTSD models, partly because of their ability to form and retrieve memories. Explanatory requirements that a comprehensive PTSD theory must have are reviewed. A connectionist neural network system called the bidirectional associative memory (BAM) is extended to encode emotion and cognition and is then shown to satisfy all PTSD explanatory requirements and consequently constitutes a comprehensive PTSD theory. Empirical work pertaining to a fundamental assumption that learning alters brain structure in ways that can be detected by neuroimaging is reviewed. Novel predictions are made, and relevance to neuroscience is discussed.

Chronic fatigue syndrome: assessing symptoms and activity level.

Current approaches to the diagnosis and assessment of Chronic Fatigue Syndrome (CFS) rely primarily on scales that measure only the occurrence of various symptoms related to CFS. Such approaches do not provide information on either the severity of symptoms or on fluctuations in symptom severity and activity level that occur over time. As a result, these measures do not reflect the complexities and the interrelations among symptoms. By obscuring the fluctuating nature of CFS and its high variability, current assessment procedures may prevent health care professionals from understanding the complexities of this disease. The present study provides two CFS case studies to illustrate the advantages of using self-reporting rating scales in combination with a device used to measure the frequency and intensity of activity. The implications of this assessment system, which captures the symptom dynamics and variability involved in CFS, are discussed.

A neural network explanation of posttraumatic stress disorder.

An introduction to connectionistic neural networks and their importance for behavior therapists was provided by Tryon (1995a). This article shows that the bidirectional associative memory connectionistic neural networks model meets all four of Jones and Barlow's (1990) requirements and all five of Brewin, Dalgleish, and Joseph's (1996) requirements for a theoretical explanation of posttraumatic stress disorder (PTSD). The bidirectional associative memory model provides a theoretical basis for explaining the clinical symptom constellation of PTSD, with special emphasis on why trauma is re-experienced through memory; accounts for individual variation in symptom severity, including why some people do not develop PTSD; explains why persons with PTSD are comorbid with depression, generalized anxiety, and substance abuse; explains how abnormal behavior derives from normal memory formation processes; and makes novel predictions.

Effectiveness of attention training in schizophrenia.

This study assessed the impact of attention training on information processing in schizophrenia. Fifty-four inpatients with chronic schizophrenia were randomly assigned to two groups after baseline assessment with the Continuous Performance Test (CPT). Patients in the experimental group participated in individual sessions of computerized attention remediation, while patients in the control group participated in individual sessions during which they viewed video documentaries. After 18 sessions, reassessment with the CPT showed that patients in the experimental group had made significantly more improvement than the control group, which made no significant change. Brief Psychiatric Rating Scale assessments before and after the study phase indicated that both groups improved on the total score but the experimental group made significantly more improvement. These results suggest that it is feasible to use practice and behavioral learning to remediate a core attention deficit in chronic schizophrenia.

Chronic fatigue syndrome: relationships of self-ratings and actigraphy.

Chronic Fatigue Syndrome is a baffling disease potentially affecting millions of Americans. Self-rating scales were developed to assess this condition but have yet to be validated with objective measures of activity. The present study of a 45-yr.-old man evaluated the relationships between scores on self-rating scales used to measure Chronic Fatigue Syndrome and actigraphy. Measured activity was related to predictors of fatigue but not to fatigue. The implications of these findings are discussed.

Activity measurements support dimensional assessment.

The Diagnostic and Statistical Manual approach to motor excess has been to treat it as a categorical variable whose presence functions as an inclusion criterion. Motor excess is thought to occur primarily during structured settings that maximize attentional demands. Activity is rarely measured as a dimensional attribute despite availability of a wide variety of suitable instruments for more than a decade (Tryon, 1985). The present study measured activity using electronic step counters in structured and unstructured school settings, commuting from home to school and back home, and at home for 2 consecutive weeks in 60 children selected from 450 children using Factor IV (hyperactivity) scores from the Conners Teacher Rating Scale to represent three levels of hyperactivity. Results indicate that (a) children rated as hyperactive are measurably more active than children rated as normally active in unstructured as well as structured situations, (b) measured activity correlates consistently and substantially with rated activity in unstructured and structured situations, and (c) a single activity factor characterizes measured activity in all situations except for class transitions during school. These results and other published findings support a quantitative (dimensional) rather than qualitative (categorical) approach to motor excess.

Synthesizing animal and human behavior research via neural network learning theory.

Animal and human research have been "divorced" since approximately 1968. Several recent articles have tried to persuade behavior therapists of the merits of animal research. Three reasons are given concerning why disinterest in animal research is so widespread: (1) functional explanations are given for animals, and cognitive explanations are given for humans; (2) serial symbol manipulating models are used to explain human behavior; and (3) human learning was assumed, thereby removing it as something to be explained. Brain-inspired connectionist neural networks, collectively referred to as neural network learning theory (NNLT), are briefly described, and a spectrum of their accomplishments from simple conditioning through speech is outlined. Five benefits that behavior therapists can derive from NNLT are described. They include (a) enhanced professional identity derived from a comprehensive learning theory, (b) improved interdisciplinary collaboration both clinically and scientifically, (c) renewed perceived relevance of animal research, (d) access to plausible proximal causal mechanisms capable of explaining operant conditioning, and (e) an inherently developmental perspective.

Psychomotor retardation found in college students seeking counseling.

Psychomotor retardation (PMR) has been documented for inpatient populations. Futterman and Tryon (1994) [Journal of Behavior Therapy and Experimental Psychiatry, 25, 41-48] provided the first report of PMR in a female outpatient sample. Because 8 of their 11 depressed Ss were receiving medication, the possibility remains that Futterman and Tryon's findings were due to medication side effects. The present study documents PMR in a nonmedicated male and female college population. Two-week, 24-h per day, content-valid behavioral measurements were obtained using step-counters from 73 college students seeking counseling. The 20 males and 53 females completed the Inventory to Diagnose Depression, the State-Trait Anxiety Inventory, the Marlowe-Crowne Social Desirability Inventory, and a structured interview. Regression analysis revealed that depression was negatively related to daytime activity. Significant age and gender effects were statistically controlled.

Psychomotor retardation found in depressed outpatient women.

Psychomotor retardation (PMR) has been found consistently in depressed inpatients. This article is the first to report PMR in depressed women outpatients in contrast to matched nondepressed controls, despite heterogeneous differences in lifestyle, using 2-week content-valid behavioral measurement. Principal findings include significant and substantial daytime activity reduction not explained by seven covariates. The absence of significant nighttime difference is explained on the basis of instrumentation limits.

Estimating and testing autocorrelation with small samples: a comparison of the C-statistic to a modified estimator.

Huitema and McKean (Psychological Bulletin, 110, 291-304, 1991) recently showed, in a Monte-Carlo study, that five conventional estimators of first-order autocorrelation perform poorly for small (< 50) sample sizes. They suggested a modified estimator and a test for autocorrelation. We examine an estimator not considered by Huitema and McKean: the C-statistic (Young, Annals of Mathematical Statistics, 12, 293-300, 1941). A Monte-Carlo study of the small sample properties of the C-statistic shows that it performs as well or better than the modified estimator suggested by Huitema and McKean (1991). The C-statistic is also shown to be closely related to the d-statistic of the widely used Durbin-Watson test.

The role of motor excess and instrumented activity measurement in attention deficit hyperactivity disorder.

Motor excess was once recognized as a primary aspect of childhood behavior disorder but has been largely discounted by current investigators despite consistent reference to hyperactivity in titles of articles, chapters, and books. The presumed minor relevance of hyperactivity to attention deficit hyperactivity disorder (ADHD) is based on analogue assessment procedures that remain to be validated. Results of content-valid instrumented behavioral measurements show that ADHD children are pervasively hyperactive. These findings are consistent with recent research showing activity to be an important aspect of temperament and a well-documented factor of externalizing disorders of childhood. Theoretical analyses of the relationship between hyperactivity and ADHD disorder are presented.

Activity decreases as percentage overweight increases.

The purpose of the present research was to clarify the empirical relationship between percentage overweight and degree of ambulatory activity. Two week activity measurements were obtained, over two studies, using pedometers, from 127 women aged 19 to 55 years ranging from 14% underweight to 99% overweight. Regression analysis indicated that activity decreased by 7.6457 x 10(-4) mph for every 1% increase in percentage overweight from 0.25279 mph associated with zero percentage overweight. These data are in good agreement with data published by Chirico and Stunkard in 1960.16 Implications for small activity increases on obesity and general health are discussed.

Evaluation of mental health. Issues of memory in the Diagnostic Interview Schedule.

Research on the Diagnostic Interview Schedule, the chief instrument in contemporary studies in psychiatric epidemiology, has supported its utility in enabling lay interviewers to reproduce psychiatric interviews within an acceptable margin of error. Nonetheless, we propose that the Diagnostic Interview Schedule commits itself to dubious assumptions regarding the accuracy of human memory, shared by other history-taking efforts, by relying on retrospective reports of lifetime DSM-III symptoms and episodic dating of symptom spells. For more than a century, the fallibility of human memory has been the topic of intensive experimental and naturalistic study, a history which is relevant to the construction of instruments like the Diagnostic Interview Schedule. The continuing use of retrospective lifetime symptom reports suggests that this literature has been largely ignored in the development and administration of the Diagnostic Interview Schedule. Prospectively organized research is needed to disclose the limits of human memory for recent psychiatric events and the mediating conditions under which memory for such events can be accurately retrieved and improved.

Issues of validity in the Diagnostic Interview Schedule.

The Diagnostic Interview Schedule, the chief instrument in contemporary studies in psychiatric epidemiology, enhances the reliability of psychiatric diagnosis and enables lay interviewers to closely reproduce psychiatric interviews. However, despite frequent references in the literature to the validity of the Diagnostic Interview Schedule, most studies fundamentally represent variations of reliability paradigms to the neglect of criterion-related validity. Mistaken assertions of validity persist in the psychometric language used to describe the Diagnostic Interview Schedule. This article examines the basis for claims and counterclaims of validity in accordance with standard psychometric definition, and identifies sources of erroneous reasoning in attempts to infer validity from reliability. The article presents a general framework organizing the process of diagnostic validation and discusses strategies for research seeking to validate psychiatric diagnoses achieved through the Diagnostic Interview Schedule.

Classical conditioning of meaning--II. A replication and triplet associative extension.

The meaning associated with verbal stimuli is modifiable by classical conditioning, suggesting that such "language conditioning" may be used clinically to modify a client's maladaptive associative history. The current research investigated the existence and generalizability of this phenomenon by attempting to replicate Staats and Staats' (1957) language conditioning effect and then extend it to a triplet conditioning paradigm (CS2----CS1----UCS). Previous research by the current authors replicated language conditioning, yet failed to extend it to a higher-order situation. Significant conditioning was obtained to the CS1, particularly for aware subjects, but no conditioning occurred to the CS2. Implications for verbal conditioning theory and clinical practice are discussed.