Motion aftereffect of combined first-order and second-order motion

When, after prolonged viewing of a moving stimulus, a stationary (test) pattern is presented to an observer, this results in an illusory movement in the direction opposite to the adapting motion. Typically, this motion aftereffect (MAE) does not occur after adaptation to a second-order motion stimulus (i.e. an equiluminous stimulus where the movement is defined by a contrast or texture border, not by a luminance border). However, a MAE of second-order motion is perceived when, instead of a static test pattern, a dynamic test pattern is used. Here, we investigate whether a second-order motion stimulus does affect the MAE on a static test pattern (sMAE), when second-order motion is presented in combination with first-order motion during adaptation. The results show that this is indeed the case. Although the second-order motion stimulus is too weak to produce a convincing sMAE on its own, its influence on the sMAE is of equal strength to that of the first-order motion component, when they are adapted to simultaneously. The results suggest that the perceptual appearance of the sMAE originates from the site where first-order and second-order motion are integrated.     

Axiomatic foundations of the Marxian Theory of Value

The aim of the present paper is to provide a logical reconstruction of the Marxian Theory of Value. This reconstruction is based upon the concept of abstract as opposed to that of homogeneous labor. Abstract labour is a social relation that holds in a market economy, (at least) whenever the profit rate is uniform; it consists in a comparison of the different labors through the exchange relationship. The author proved in a different place (see García de la Sienra, 1987) that there exists a mathematical representation of abstract labor which is unique up to similarity transformations. The existence of this function — which is none other than the value function — is the basis of the present axiomatization, which includes detailed reconstructions of two of the most important models of the theory.     

Young Muslim Women in France: Cultural and Psychological Adjustments

Even though France has experienced increasing and inevitable feminization in its immigrant population since 1974, research has tended to ignore the role of immigrant women, especially Muslim women, in the migration process. Public attention has been diverted by concern over such relatively marginal issues as the headscarf affair, and insufficient attention has been paid to the important role Muslim women play in France, especially those coming from Algeria. These women function as cultural mediators between the traditional culture of the sending country and the modern one of the host country. They see themselves as both tradition-bearers and integration proponents. The demands of immigration have given rise to the growth and development of different leaders, among them cultural mediators seeking a bridge between Islam and modernity, economic mediators seeking to establish women in the media and as entrepreneurs, and political mediators who seek access to power at the local level for the immigrants. These new mediators will eventually shape a new generation of female actors very far from the traditional countries of origin, although for the time being they still suffer from the inequality of rights for women and chances in their overall social life.     

Discrimination of 3-D shape and 3-D curvature from motion in active vision

We examined the ability of human observers to discriminate between different 3-D quadratic surfaces defined by motion, and with head position fed back to the stimulus to provide an up-to-date dynamical perspective view. We tested whether 3-D shape or 3-D curvature would affect discrimination performance. It appeared that discrimination of 3-D quadratic shape clearly depended on shape but not on the amount of curvature. Even when the amount of curvature was randomized, subjects’ performance was not altered. On the other hand, the discrimination of 3-D curvature clearly depended linearly on curvature with Weber fractions of 20% on the average and, to a small degree, on 3-D shape. The experiment shows that observers can easily separate 3-D shape and 3-D curvature, and that Koenderink’s shape index and curvedness provide a convenient way to specify shape. These results warn us against using just any arbitrary 3-D shape in 3-D shape perception tasks and indicate, for example, that emphasizing 3-D shape in computer displays by exaggerating curvature does not have any effect.     

A comment on ‘some standard errors in item response theory’

In maximum likelihood estimation the standard error of the location parameter of the three parameter logistic model can be large, due to inaccurate estimation of the lower asymptote. Thissen and Wainer who demonstrated this effect, suggested that the introduction of a prior distribution for the lower asymptote might alleviate the problems. Here it is demonstrated in some detail that the standard error of the location parameter can be made acceptably small in this way.The author thanks Pieter Vijn for his helpful comments.     

Linear relations amongk sets of variables

A family of solutions for linear relations amongk sets of variables is proposed. It is shown how these solutions apply fork=2, and how they can be generalized from there tok3.The family of solutions depends on three independent choices: (i) to what extent a solution may be influenced by differences in variances of components within each set; (ii) to what extent the sets may be differentially weighted with respect to their contribution to the solution—including orthogonality constraints; (iii) whether or not individual sets of variables may be replaced by an orthogonal and unit normalized basis.Solutions are compared with respect to their optimality properties. For each solution the appropriate stationary equations are given. For one example it is shown how the determinantal equation of the stationary equations can be interpreted.     

Abnormal and normal obsessions

Three related, exploratory studies were carried out in order to ascertain the occurrence and nature of normal obsessions, and to relate them to abnormal obsessions. The subjects included 8 obsessional patients, and up to 124 non-clinical subjects.Broadly, the findings were that normal obsessions are a common experience and they resemble the form of abnormal obsessions. They also show some notable similarities of content. However normal and abnormal obsessions differ in several respects, including frequency, duration, intensity and consequences, among others.With repeated practice, the frequency, duration and discomfort of obsessions are observed to decrease. Overall, the findings are considered to be consistent with the noxious stimulus cum habituation theory.     

Insulin and glucagon as determinants of body weight set point and microregulation in rats

Seven adult male rats were observed for body weight and microregulation (feeding, drinking, and running patterns) after manipulation of insulin and glucagon levels. They received three injections per day for 3 days each week of 3 U of protamine zinc insulin, .25 mg of zinc glucagon, 50 microgram of protamine zinc somatostatin (SRIF), or protamine zinc vehicle. Diabetes was then induced with an iv injection of streptozotocin (65 mg/kg), and the injection schedule was repeated after the full diabetic syndrome emerged. In all rats whose insulin levels were increased relative to glucagon levels, body weight increased; in those whose glucagon levels were increased relative to insulin levels, body weight decreased. All injections except vehicle reduced meal sizes in both normal and diabetic rats, but only insulin increased the frequency of feeding. These effects could be predicted by the glucostatic theory of food intake regulation and are thus interpreted as supportive of this theory. These results also support the hypothesis that the relative concentration of insulin to glucagon is a regulator of body weight set point.