The Observation of Incremental Validity Does Not Always Mean Unique Contribution to Prediction

Statistical analyses require proper interpretation. Misinterpretation leads to a lack of understanding of the relationships among variables. Worse, it can lead to misunderstanding of these relationships, which sometimes lead researchers and practitioners to infer the presence of a source of variance that is not present. This is especially true in regression where increased predictiveness from an additional variable may be due to either common or specific variance. In many instances, erroneous interpretation leads to erroneous attribution of the source of the improved prediction. Three examples are provided and methods for detecting specific variance are suggested.     

Kinematic motion analysis and muscle activation patterns of continuous reaching in survivors of stroke

Coordinated reaching requires continuous interaction between the efferent motor output and afferent feedback; this interaction may be significantly compromised following a stroke. The authors sought to characterize how survivors of stroke generate continuous, goal-directed reaching. Sixteen survivors of stroke completed functional testing of the stroke-affected side and a continuous reaching task between 2 targets with both sides. Motion analysis and electromyography data were collected to determine segmental contributions to reach (e.g., amount of compensatory trunk), spatiotemporal parameters (e.g., peak velocities), and muscle activation patterns (MAP). Repeated measures analyses of variance compared how survivors of stroke reach with the stroke-affected versus less affected sides. Correlations were determined between kinematic outcomes and functional ability. Participants used significantly more trunk movement and less shoulder flexion and elbow extension when reaching with the stroke-affected side. This corresponded with less muscle activity in the proximal musculature including the anterior, middle, and posterior deltoid on the stroke-affected side. There were significant correlations between the segmental contributions to reach, functional ability, and MAPs. Survivors of stroke generate reduced MAPs in the stroke-affected side corresponding to altered segmental kinematics and function ability. These findings suggest that impairments in the ability to generate sufficient MAPs may contribute to the difficulty in generating continuous reaching motions.     

Iontophoretically applied potassium ions as an experimental pain stimulus for investigating pain mechanisms

The present study investigated the psychophysical characteristics of potassium iontophoresis and its suitability as an experimental pain stimulus. Experiment 1 investigated the optimal duration of the pain stimulus for reliable reporting across repeated trials and whether the relationship between stimulus and subject response was linear, logarithmic, or a power function. In Experiment 2, the optimal interstimulus interval (ISI) was determined for reliable pain reporting, and stimulus history effects, both in terms of session effects and the effects of immediately preceding stimuli, were evaluated. In Experiment 3, potassium iontophoresis was compared with a sodium iontophoresis control. Linear functions described the stimulus-pain relationship best. No significant differences in the goodness-of-fit coefficients of determination, correlations, or coefficients of variation were found for the stimulus durations of 1, 2, and 4 sec. Significant stimulus history effects were found across a session, with adaptation and enhancement of responding for low- and moderate-intensity stimuli, respectively. The effects of the immediately preceding stimuli were suppression or enhancement of pain response, depending on the ISI, the preceding stimulus intensity, and the present stimulus intensity. Potassium iontophoresis was a significantly more effective pain stimulus than was sodium iontophoresis. It was concluded that potassium iontophoresis is a convenient and reliable experimental pain stimulus, which can be presented rapidly and repeatedly with minimal loss in consistency of subject pain report. Potassium iontophoresis provides a tool for investigating the neural modulation of pain in the relative absence of inflammation processes and tissue damage.     

Psychic development and the group analytic situation

Psychic development can be viewed as the emergence and establishment of coherency which is an aspect of organization. This paper discusses the concept of coherency and reviews some early developmental processes in the mother/infant interaction that establish coherency. The development of the matrix of the analytic group is viewed as the establishment and development of group coherency. Finally, the link between the development of individual coherency and group coherency is outlined.Dr. Malcolm Pines is a Consultant Psychotherapist at Tavistock Clinic, founder member of the Institute of Group Analysis (London), member of the British Psychoanalytical Society, and Past President of the International Association of Group Psychotherapy.     

VALUE SYSTEMS OF STUDENTS IN PAPUA NEW GUINEA AND AUSTRALIA

The Rokeach Value Survey was administered to 12 groups of indigenous respondents fluent in the English language and enrolled in tertiary institutions and training programmes in Papua New Guinea (over 1,100 subjects). Average value systems of these respondents were compared with those of three Australian student groups (secondary and tertiary). Marked differences were found in the relative importance assigned to particular values. Values assigned relatively high importance by the Papua New Guinea groups were discussed in relation to lower-order safety and security needs that may become salient in a developing country, and in terms of the traditional culture and the history of Papua New Guinea, especially the missionary influence, the extended family and wantok (”one-talk”) systems, possible expatriate influence on occupational roles, and present concern with emerging nationhood. Values assigned relatively high importance by the Australian groups were discussed in relation to higher-order needs that might become prepotent in a more affluent society. Factor analyses indicated that all 12 groups in Papua New Guinea were fairly similar in their average value systems.     

An apparent new instance of stimulus intensity dynamism during discrimination of duration of repeating auditory stimuli

Rats were trained on a VI/EXT discrimination using barpressing in a Skinner box for food reinforcement. The discriminanda consisted of different proportions of noise to silence within a fixed 3^-s noise-plus-silence repeating cycle. These stimuli were easily discriminated by human subjects, but the rats formed the discrimination only poorly and after considerable training. Analysis of response rates during noise and silence separately within the 3^-s noise-plus-silence cycle showed higher response rates during noise, irrespective of whether this was during the positive or during the negative stimulus, or whether relatively long duration of noise or relatively short duration of noise (within the 3^-s cycle) constituted the positive stimulus. These results are seen as providing an instance of the dynamogenic effects of stimulus intensity on response vigour to which the Perkins-Logan generalization of inhibition hypothesis of stimulus intensity dynamism cannot apply.     

Triangles in ROC space: History and theory of “nonparametric” measures of sensitivity and response bias

Can accuracy and response bias in two-stimulus, two-response recognition or detection experiments be measured nonparametrically? Pollack and Norman (1964) answered this question affirmatively for sensitivity, Hodos (1970) for bias: Both proposed measures based on triangular areas in receiver-operating characteristic space. Their papers, and especially a paper by Grier (1971) that provided computing formulas for the measures, continue to be heavily cited in a wide range of content areas. In our sample of articles, most authors described triangle-based measures as making fewer assumptions than measures associated with detection theory. However, we show that statistics based on products or ratios of right triangle areas, including a recently proposed bias index and a not-yetproposed but apparently plausible sensitivity index, are consistent with a decision process based on logistic distributions. Even the Pollack and Norman measure, which is based on non-right triangles, is approximately logistic for low values of sensitivity. Simple geometric models for sensitivity and bias are not nonparametric, even if their implications are not acknowledged in the defining publications.     

Air force officer qualifying test validity for predicting pilot training performance

The AFOQT was validated for the prediction of pilot training criteria. Subjects were 7,563 men and women selected for pilot training on the basis of educational attainment and AFOQT scores. Criterion variables included daily flight training grades, check flight grades in subsonic and transonic aircraft, and overall academic performance in the 53 week pilot training course. Test validities were presented as observed, corrected for multivariate range restriction, and corrected for multivariate range restriction and unreliability. The Aviation Information and Instrument Comprehension tests, measures of job knowledge, were most predictive of daily and check flights in the initial subsonic jet aircraft. This reflects the relative greater importance of prior job knowledge early in training. The Scale Reading test, a measure of perceptual speed, was most predictive for daily and check flights in the advanced transonic training aircraft. The Arithmetic Reasoning test, a good measure of general cognitive ability, was most predictive of aeronautics in ground school. The development of an improved pilot selection composite is suggested by the results of the validity analyses.The views expressed are those of the authors and not necessarily those of the Department of the Air Force, Department of Defense, or the Government of the United States.     

Safe and Unsafe Sexual Intentions and Behavior: The Effects of Norms and Attitudes1

A study of 85 heterosexual men, 85 heterosexual women, and 82 homosexual men was undertaken to examine the variables that influence intentions to engage in different sexual practices and actual sexual behavior. On the basis of Fishbein and Ajzen's (1975) theory of reasoned action, it was predicted that the strength of intentions would be related to whether behavior was in accord with intentions. Consistent with expectations, the strength of intention to engage in six different sexual practices (e. g., vaginal intercourse, anal intercourse, oral sex) and the three strategies that modify the risk of HIV transmission (sex with an exclusive partner, sex wearing a condom, and looking for a new partner) predicted actual behavior. Second, it was proposed that attitudes toward one's sexual practices and norms would be related to intentions to engage in safe sex. To reflect differential levels in the safety of behavioral intentions, five safety intention groups were formed: (a) nonpenetrative sex, (b) penetrative sex in an exclusive relationship with a condom, (c) penetrative sex in an exclusive relationship without a condom, (d) penetrative sex in a nonexclusive relationship with a condom, and (e) penetrative sex in a nonexclusive relationship without a condom. Norms, rather than attitudes, distinguished the five safety intention groups. the groups intending to engage in safe sex (nonpenetrative sex or penetrative sex with a condom) perceived lower levels of social approval for their sexual practices than the noncondom groups. Additional analyses showed that past behavior had a stabilizing effect on the intention-behavior relationship, but only for the nonpenetrative and noncondom safety intention groups.