Does monocular visual space contain planes?

The issue of the existence of planes—understood as the carriers of a nexus of straight lines—in the monocular visual space of a stationary human observer has never been addressed. The most recent empirical data apply to binocular visual space and date from the 1960s (Foley, 1964). This appears to be both the first and the last time this basic issue was addressed empirically. Yet the question is of considerable conceptual interest. Here we report on a direct empirical test of the existence of planes in monocular visual space for a group of sixteen experienced observers. For the majority of these observers monocular visual space lacks a projective structure, albeit in qualitatively different ways. This greatly reduces the set of viable geometrical models. For example, it rules out all the classical homogeneous spaces (the Cayley-Klein geometries) such as the familiar Luneburg model. The qualitatively different behavior of experienced observers implies that the generic population might well be inhomogeneous with respect to the structure of visual space.     

On angry leaders and agreeable followers. How leaders' emotions and followers' personalities shape motivation and team performance

Do followers perform better when their leader expresses anger or when their leader expresses happiness? We propose that this depends on the follower's level of agreeableness. Anger is associated with hostility and conflict-states that are at odds with agreeable individuals' goals. Happiness facilitates affiliation and positive relations-states that are in line with agreeable individuals' goals. Accordingly, the two studies we conducted showed that agreeableness moderates the effects of a leader's emotional displays. In a scenario study, participants with lower levels of agreeableness responded more favorably to an angry leader, whereas participants with higher levels of agreeableness responded more favorably to a neutral leader. In an experiment involving four-person teams, teams composed of participants with lower average levels of agreeableness performed better when their leader expressed anger, whereas teams composed of participants with higher average levels of agreeableness performed better when their leader expressed happiness. Team performance was mediated by experienced workload, which was highest among agreeable followers with an angry leader. Besides having important practical implications, the findings shed new light on the fundamental question of how emotional expressions regulate social behavior.     

Pathologisches Kaufen

Compulsive buying (CB) is characterized by the senseless und uncontrollable acquisition of items. The main focus is on the act of buying and the purchased items are afterwards hardly used or not even at all. The repeated excessive behavior leads to psychological, social and financial problems. In addition to their buying behavior most individuals with CB also suffer from other mental disorders, especially depression, anxiety disorders, personality disorders and impulse control disorders. There is an ongoing discussion about the appropriate diagnosis and currently CB is classified as an impulse control disorder not otherwise specified. In the treatment of CB controlled psychotherapy studies indicated the efficacy of cognitive behavioral therapy while the benefit of pharmacotherapy still needs to be confirmed. Additional research is necessary concerning classification, etiology and the development of differential therapy programs.     

Repeating a strongly masked stimulus increases priming and awareness

Previous studies [Marcel, A. J. (1983). Conscious and unconscious perception: Experiments on visual masking and word recognition. Cognitive Psychology, 15(2), 197–237; Wentura, D., & Frings, C. (2005). Repeated masked category primes interfere with related exemplars: New evidence for negative semantic priming. Journal of Experimental Psychology: Learning, Memory, and Cognition, 31(1), 108–120] suggested that repeatedly presenting a masked stimulus improves priming without increasing perceptual awareness. However, neural theories of consciousness predict the opposite: Increasing bottom-up strength in such a paradigm should also result in increasing availability to awareness. Here, we tested this prediction by manipulating the number of repetitions of a strongly masked digit. Our results do not replicate the dissociation observed in previous studies and are instead suggestive that repeating an unconscious and attended masked stimulus enables the progressive emergence of perceptual awareness.     

How robust are the deviations in haptic parallelity?

Several studies have shown that physically parallel bars do not feel parallel and vice versa. The most plausible cause of this deviation is the biasing influence of an egocentric reference frame. The aim of the present study was to assess the strength of this egocentric contribution. The deviations from veridicality were measured in six experiments where subjects were presented with either haptic or visual information about parallelity or their deviations. It was found that even direct error feedback (either haptically or visually) did not even nearly result in veridical performance. The improvements found were attributed to a shift in focus towards a more allocentric reference frame, possibly reflecting the same mechanisms as found in delay and noninformative vision studies. We conclude that the illusionary percept of haptic parallelity is rather robust and is indeed caused by a strong reliance on an egocentric reference frame.     

The effects of curvature on haptic judgments of extent in sighted and blind people

A series of experiments was carried out to examine the effect of curvature on haptic judgments of extent in sighted and blind individuals. Experiment 1 showed that diameters connecting the endpoints of semicircular lines were underestimated with respect to straight lines, but failed to show an effect of visual experience on length judgments. In experiment 2 we tested are lengths. The effects of curvature on perceived path length were weaker, but were still present in this experiment. Visual experience had no effect on path length judgments. Another experiment was performed to examine the effect of repeated tracing (1, 5, 9, or unlimited number of traces) on judgments of the lengths of straight lines and diameters of semicircles. Judgments of extent were more accurate when subjects engaged in larger numbers of traces. There was no effect of number of traces on curve-height judgments, suggesting that subjects were not using height estimates to judge diameters of semicircles. In a further experiment we tested the effect of number of traces on curves that varied in height. Restricting subjects to a single trace magnified the effect of path length on judgments of the distance between the endpoints of curves. Additional experiments showed that curvature effects on diameter judgments were not eliminated when stimuli were in the frontal plane or when the curves were explored with the use of two hands. Arm support had no effect on judged length in experiment 7. A final experiment showed a robust horizontal vertical illusion in haptic perception of convex curves, with overestimation of the heights of the curves compared with their widths. The practical and theoretical implications of the results are discussed.     

The influence of picture size on recognition and exploratory behaviour in raised-line drawings

We demonstrate the influence of picture size on haptic recognition and exploratory behaviour. The stimuli were raised-line drawings of everyday objects. Participants were instructed to think aloud during haptic exploration of the pictures. We measured the delay between initial correct speculation and final correct response. The results indicate that picture size influences accuracy but not response latency: large drawings are recognised more often but not faster. By analysing video recordings of the experiment we found that two-handed exploration increases when picture size increases and that, on average, 83% of the exploration time involves the use of two hands. The thinking-aloud data showed that the average time difference between the initial correct speculation and final correct response amounted to 23% of the total reaction time. We discuss our results with respect to the design of tactile aids and the ecological validity of single-finger exploration.     

Haptic curvature comparison of convex and concave shapes

A sculpture and the mould in which it was formed are typical examples of objects with an identical, but opponent, surface shape: each convex (ie outward pointing) surface part of a sculpture has a concave counterpart in the mould. The question arises whether the object features of opponent shapes can be compared by touch. Therefore, we investigated whether human observers were able to discriminate the curvatures of convex and concave shapes, irrespective of whether the shape was convex or concave. Using a 2AFC procedure, subjects had to compare the curvature of a convex shape to the curvature of a concave shape. In addition, results were also obtained for congruent shapes, when the curvature of either only convex shapes or only concave shapes had to be compared. Psychometric curves were fitted to the data to obtain threshold and bias results. When subjects explored the stimuli with a single index finger, significantly higher thresholds were obtained for the opponent shapes than for the congruent shapes. However, when the stimuli were touched by two index fingers, one finger per surface, we found similar thresholds. Systematic biases were found when the curvature of opponent shapes was compared: the curvature of a more curved convex surface was judged equal to the curvature of a less curved concave surface. We conclude that human observers had the ability to compare the curvature of shapes with an opposite direction, but that their performance decreased when they sensed the opponent surfaces with the same finger. Moreover, they systematically underestimated the curvature of convex shapes compared to the curvature of concave shapes.