Handgrip maximum force and the visual horizontal-vertical illusion

The visual horizontal-vertical illusion (HVI) refers to the tendency to overestimate vertical distances relative to horizontals in both 2-D and 3-D presentations. Although the HVI is evident across a wide range of different stimuli, no general theoretical account fully explains the illusion. Some recent authors have proposed the 'effort' account of HVI, contending that vertical overestimation is mediated by effort assessment of gravitational challenges offered by the stimulus. The theory has been supported by a set of studies showing that the height overestimation of large-scale 3-D objects is inversely related to perceivers' fitness and strength. We explored if the large-scale HVI/strength dependence extends to the evaluation of small-scale 2-D line stimuli, traditionally used in HVI studies. We measured the maximum handgrip strength, and assessed the HVI with a computerised line-adjustment task in thirty-two individuals. Compatible with earlier findings in the context of large-scale 3-D stimuli, a significant negative correlation was found between the strength of the dominant hand and amount of HVI. In addition, the variability of HVI was negatively correlated with maximum grip strength of both hands. The results are discussed with reference to the 'effort' account of HVI.     

The assessment of fitness to drive after a stroke: the Nordic Stroke Driver Screening Assessment

The British Stroke Driver Screening Assessment (SDSA) is a set of four simple cognitive tests to evaluate driving fitness in stroke patients. To evaluate its usefulness in a Scandinavian context, we adapted the tests and assessed a group of 97 stroke patients from Sweden and Norway, using a driving test as the criterion. When results were calculated according to the original method, based on a discriminant function, less than 70% of the participants were correctly classified. To improve the predictive potential, a new discriminant analysis was performed, using the scores of a subsample of 49 patients, and validated on the remaining 48 participants. In total, 78% of the patients were correctly classified, but specificity was superior to sensitivity. We conclude that the Nordic version of the SDSA is a useful instrument, provided that test scores are interpreted in a balanced manner, taking into account the possibility of compensatory traffic behavior.     

Odor-intensity interaction in binary and ternary mixtures

Eight subjects scaled the overall perceived odor intensity of binary and ternary mixtures of the odorous substances pyridine, acetone, and ethyl acrylate. The results concerning basic principles of additivity for binary mixtures comply with those of earlier studies. For the ternary mixtures, the degree of arithmetic additivity in odor intensity seemed lower when a third component was addedto a binary mixture than when the second component was added to-asmgle-udor, but this did not reach statistical significance. In general, the degree of arithmetic additivity inherent in the power function for single substanceswas found to be of the same size as the degree of additivity for binary as well as ternary mixtures. However, for binary mixtures, the additivity of the mixtures was found to approximatethat ofthe substancewith the lower exponent. In addition, the degree of additivity of the binary mixture was monotonically related to the average arithmetic additivity of the power functions for the two components.     

‘Preparedness’ and ‘arousability’ as determinants of electrodermal conditioning

‘Arousability’, as defined through spontaneous electrodermal responses, has been empirically linked to anxiety, phobic symptoms and outcome of systematic desensitization. Previous data from our laboratory indicate that ‘preparedness’, as defined through potentially phobic vs. fear-irrelevant or ‘neutral’ conditioned stimuh, is an important determinant of electrodermal conditioning. The present experiment compared groups selected to be high or low in spontaneous responding during differential conditioning to potentially phobic or neutral stimuh. It was found that the effects of these two factors were essentially additive, i.e. conditioning and resistance to extinction were better for phobic stimuli and for high-arousal groups. The high-aroused group with phobic stimuh showed diffuse responding during acquisition, not differentiating between reinforced and unreinforced cues. However, it was the only group that failed to extinguish during 20 trials, which indicates that high arousal gives superior resistance to extinction particularly for phobic stimuli.     

ON HOMOGENEITY OF STATES AND TRANSFER IN LEARNING TO CATEGORIZE

Two groups of subjects (A and B) were first trained on samples of states with different homogeneity and then tested on common samples. It was found that B learned faster with the more homogeneous samples of items. This group also performed better in terms of transfer. Both groups did better than the control group (C) on the test series. A fourth group (D) had items which, according to Weber's law, would appear less similar than those of the control group. As was to be expected, C performed better than D. The outcome may be interpreted in terms of categorization. When states leading to the same event become more homogeneous, categorization of the input information is easier, and both learning and transfer facilitated.     

The effect of polar projection on the perception of euclidean structure from motion

The aim of the present study was to examine whether euclidean structure could be recovered from apparent motion sequences under polar projection. In Experiment 1, length judgments of two sides of a simulated triangle rotating in depth did not reveal effects of type of projection, polar or parallel, on the perception of euclidean structure. However, there was a significant correlation between simulated and produced slants. The results also indicated that absolute depth judgments could not be accounted for by a random mechanism suggested by Todd and Bressan (1990). Experiments 2 and 3, in which a continuous dot surface was substituted for the triangle, showed that polar projection information from a relatively large visual angle, 17.40°, as compared with a small visual angle, 4.35°, facilitated discrimination of depth. Produced height:width ratios were consistently related to simulated shape, although the depth dimension was underestimated. Finally, Experiment 4 showed significant correlations between simulated and produced height:width ratios that could be accounted for only by an analysis in whichX andY velocities were treated independently. As in previous experiments, the variation in the depth dimension was underestimated. It was concluded that the visual system utilizes the additional information that is available in polar projection when recovering structure from motion, but that for different reasons the perceived structure does not become euclidean. These reasons are discussed briefly.     

Surrogate consent to non-beneficial research: erring on the right side when substituted judgments may be inaccurate

Part of the standard protection of decisionally incapacitated research subjects is a prohibition against enrolling them unless surrogate decision makers authorize it. A common view is that surrogates primarily ought to make their decisions based on what the decisionally incapacitated subject would have wanted regarding research participation. However, empirical studies indicate that surrogate predictions about such preferences are not very accurate. The focus of this article is the significance of surrogate accuracy in the context of research that is not expected to benefit the research subject. We identify three morally relevant asymmetries between being enrolled and not being enrolled in such non-beneficial research, and conclude that when there is a non-negligible probability that surrogates’ predictions are wrong, it will generally be better to err on the side of not authorizing enrollment.     

Genetic effects explain the stability of psychopathic personality from mid- to late adolescence

This study examined the importance of genetic and environmental influence for the stability of psychopathic personality between mid- and late adolescence. The target sample consisted of all 1,480 male and female twin pairs born in Sweden between 1985 and 1986. Psychopathic personality was measured with the Youth Psychopathic Traits Inventory (YPI; H. Andershed, M. Kerr, M. Stattin, & S. Levander, 2002) when the participants were 16 and 19 years old. Results showed that the 3 psychopathic personality dimensions were stable at different levels of analysis and linked to a stable higher order general factor (i.e., psychopathic personality factor). Genetic factors contributed substantially to the stability of this general higher order factor, whereas environmental factors were of little importance. However, the authors also found specific genetic stability in the Callous/unemotional and Impulsive/irresponsible dimension. Thus, the model provides evidence for etiologic generality and etiologic specificity for the stability of psychopathic personality between mid- and late adolescence.     

Large continuous perspective transformations are necessary and sufficient for accurate perception of metric shape

We investigated the ability to perceive the metric shape of elliptical cylinders. A large number of previous studies have shown that small perspective variations (< or =10 degrees) afforded by stereovision and by head movements fail to allow accurate perception of metric shape. If space perception is affine (Koenderink & van Doom, 1991), observers are unable to compare or relate lengths in depth to frontoparallel lengths (i.e., widths). Frontoparallel lengths can be perceived correctly, whereas lengths in depth generally are not. We measured reaches to evaluate shape perception and investigated whether larger perspective variations would allow accurate perception of shape. In Experiment 1, we replicated previous results showing poor perception with small perspective variations. In Experiment 2, we found that a 90 degrees continuous change in perspective, which swapped depth and width, allowed accurate perception of the depth/width aspect ratio. In Experiment 3, we found that discrete views differing by 90 degrees were insufficient to allow accurate perception of metric shape and that perception of a continuous perspective change was required. In Experiment 4, we investigated continuous perspective changes of 30 degrees, 45 degrees, 60 degrees, and 90 degrees and discovered that a 45 degrees change or greater allowed accurate perception of the aspect ratio and that less than this did not. In conclusion, we found that perception of metric shape is possible with continuous perspective transformations somewhat larger than those investigated in the substantial number of previous studies.     

Does singing promote well-being?: An empirical study of professional and amateur singers during a singing lesson

This study explored the possible beneficial effects of singing on well-being during a singing lesson. Eight amateur (2m, 6f, age 28–53 yrs) and eight professional (4m, 4f, age 26–49 yrs) singers who had been attending singing lessons for at least six months were included. Continuous ECG was recorded and computerized spectral analysis was performed. Serum concentrations of TNF-alpha, prolactin, cortisol, and oxytocin were measured before and 30 min after the lesson. Five visual analogue scales (VAS, sad-joyful, anxious-calm, worried-elated, listless-energetic, and tense-relaxed) were scored before and after the lesson. In addition, a semi-structured interview was performed. Heart rate variability analyses showed significant changes over time in the two groups for total power, and low and high frequency power. Power increased during singing in professionals, whereas there were no changes in amateurs. This indicates an ability to retain more “heart-brain connection,” i.e., more cardio-physiological fitness for singing in professional singers, compared to amateur singers. Serum concentration of TNF-alpha increased in professionals after the singing lesson, whereas the concentration in amateurs decreased. Serum concentrations of prolactin and cortisol increased after the lesson in the group of men and vice versa for women. Oxytocin concentrations increased significantly in both groups after the singing lesson. Amateurs reported increasing joy and elatedness (VAS), whereas professionals did not. However, both groups felt more energetic and relaxed after the singing lesson. The interviews showed that the professionals were clearly achievement-oriented, with focus on singing technique, vocal apparatus and body during the lesson. The amateurs used the singing lessons as a means of self-actualization and self-expression as a way to release emotional tensions. In summary, in this study, singing during a singing lesson seemed to promote more well-being and less arousal for amateurs compared to professional singers, who seemed to experience less well-being and more arousal.