Psychology has to deal with efferences too

The authors argue that F. Mechsner's (2004) perceptual-cognitive approach is an important contribution to the current discussion of motor control. Mechsner presents convincing evidence against direct motor control. Nevertheless, the mechanisms by which perceptual-cognitive representations determine efferent commands must still be clarified.     

Deficits of anticipatory grip force control after damage to peripheral and central sensorimotor systems

Healthy subjects adjust their grip force economically to the weight of a hand-held object. In addition, inertial loads, which arise from arm movements with the grasped object, are anticipated by parallel grip force modulations. Internal forward models have been proposed to predict the consequences of voluntary movements. Anesthesia of the fingers impairs grip force economy but the feedforward character of the grip force/load coupling is preserved. To further analyze the role of sensory input for internal forward models and to characterize the consequences of central nervous system damage for anticipatory grip force control, we measured grip force behavior in neurological patients. We tested a group of stroke patients with varying degrees of impaired fine motor control and sensory loss, a single patient with complete and permanent differentation from all tactile and proprioceptive input, and a group of patients with amyotrophic lateral sclerosis (ALS) that exclusively impairs the motor system without affecting sensory modalities. Increased grip forces were a common finding in all patients. Sensory deficits were a strong but not the only predictor of impaired grip force economy. The feedforward mode of grip force control was typically preserved in the stroke patients despite their central sensory deficits, but was severely disturbed in the patient with peripheral sensory deafferentation and in a minority of stroke patients. Moderate deficits of feedforward control were also obvious in ALS patients. Thus, the function of the internal forward model and the precision of grip force production may depend on a complex anatomical and functional network of sensory and motor structures and their interaction in time and space.     

Variable action effects: response control by context-specific effect anticipations

The ideomotor principle (IMP) claims that bidirectional associations between actions and their contingent effects are acquired so that voluntary actions are accessed by the anticipation of intended effects. Until now, evidence for the IMP exists only for stable action-effect relations. The present paper explores whether the IMP also holds true for the initiation of actions for which no unconditional contingent action-effect relations exist. Participants responded with left and right key presses in two different contexts. They selected the responses according to the vertical (context A) or horizontal (context B) position of a target. Responses were followed by short/fast movements of the target in context A and comparatively long/slow movements in context B. Consequently, each response produced short and long effects equally often in both contexts. Nevertheless, RTs decreased in contexts with short effects and increased in contexts with long effects. Data confirm that action-effect associations were acquired context-specifically and that the same actions were accessed by different effect anticipations.     

Decision making under internal uncertainty: the case of multiple-choice tests with different scoring rules

This paper assesses framing effects on decision making with internal uncertainty, i.e., partial knowledge, by focusing on examinees' behavior in multiple-choice (MC) tests with different scoring rules. In two experiments participants answered a general-knowledge MC test that consisted of 34 solvable and 6 unsolvable items. Experiment 1 studied two scoring rules involving Positive (only gains) and Negative (only losses) scores. Although answering all items was the dominating strategy for both rules, the results revealed a greater tendency to answer under the Negative scoring rule. These results are in line with the predictions derived from Prospect Theory (PT) [Econometrica 47 (1979) 263]. The second experiment studied two scoring rules, which allowed respondents to exhibit partial knowledge. Under the Inclusion-scoring rule the respondents mark all answers that could be correct, and under the Exclusion-scoring rule they exclude all answers that might be incorrect. As predicted by PT, respondents took more risks under the Inclusion rule than under the Exclusion rule. The results illustrate that the basic process that underlies choice behavior under internal uncertainty and especially the effect of framing is similar to the process of choice under external uncertainty and can be described quite accurately by PT.     

Self-pity: exploring the links to personality,control beliefs,and anger

Self-pity is a frequent response to stressful events. So far, however, empirical research has paid only scant attention to this subject. The present article aims at exploring personality characteristics associated with individual differences in feeling sorry for oneself. Two studies with N = 141 and N = 161 university students were conducted, employing multidimensional measures of personality, control beliefs, anger, loneliness, and adult attachment. With respect to personality, results showed strong associations of self-pity with neuroticism, particularly with the depression facet. With respect to control beliefs, individuals high in self-pity showed generalized externality beliefs, seeing themselves as controlled by both chance and powerful others. With respect to anger expression, self-pity was primarily related to anger-in. Strong connections with anger rumination were also found. Furthermore, individuals high in self-pity reported emotional loneliness and ambivalent-worrisome attachments. Finally, in both studies, a strong correlation with gender was found, with women reporting more self-pity reactions to stress than men. Findings are discussed with respect to how they support, extend, and qualify the previous literature on self-pity, and directions for future empirical research are pointed out.     

Consensus effects in categorization decisions

A previous study (Gilat et al., J. Exp. Psychol. Appl. 3 (1997) 83) has shown that the incentive to reach consensus can raise the tendency to rely on base rates in signal detection decisions and can reduce the probability that less likely events will be accurately classified. This phenomenon was named the “consensus effect”. The current study assesses the conditions under which this effect develops and in particular the effects of information about the game and of the incentive structure on the learning process. The results of three experiments show that the learning process slows when participants have information about the actual state of nature. This finding is captured by a reinforcement learning model with the assumption that information narrows the distribution of the initial propensities for choosing among cutoffs. The results are further evidence for the utility of the combination of learning models and analyses of cognitive processes for the prediction of decision making in situations involving multiple players.     

Philosophical reflections on the foundations of mathematics

This article was written jointly by a philosopher and a mathematician. It has two aims: to acquaint mathematicians with some of the philosophical questions at the foundations of their subject and to familiarize philosophers with some of the answers to these questions which have recently been obtained by mathematicians. In particular, we argue that, if these recent findings are borne in mind, four different basic philosophical positions, logicism, formalism, platonism and intuitionism, if stated with some moderation, are in fact reconcilable, although with some reservations in the case of logicism, provided one adopts a nominalistic interpretation of Plato's ideal objects. This eclectic view has been asserted by Lambek and Scott (LS 1986) on fairly technical grounds, but the present argument is meant to be accessible to a wider audience and to provide some new insights.     

Effects of two-year treatment with the cholinesterase inhibitor rivastigmine on behavioural symptoms in Alzheimer's disease

Alzheimer's disease (AD) is accompanied by prominent behavioural disturbances. They cause significant distress for both caregivers and patients and can play a major role in the decision to institutionalise AD patients. Recent evidence suggests that cholinergic deficiencies not only contribute to the memory and cognitive abnormalities of AD but are also responsible for some behavioural abnormalities seen over the course of the disease. In this study we assessed the ability of rivastigmine, a pseudo-irreversible cholinesterase inhibitor, to improve behavioural and psychopathologic symptoms in AD. The analysis included 34 patients present in the Germanarm of the international study B303 who received and completed long-term treatment with rivastigmine in the open-label study B305. Assessments of behaviour and psychopathological symptoms were performed using the behavioural component of the Clinicians Interview Based Impression of Change Plus (CIBIC-Plus). Results show that long-term treatment with rivastigmine can slow the progression of behavioural and psychopathological symptoms of AD. Behavioural symptoms showing stabilisation included aggressiveness, activity disturbances, hallucinations and paranoid features. Results also suggest that patients treated earlier with rivastigmine may attain a greater benefit compared with patients whose treatment is delayed 6 months. Further studies examining the effects of rivastigmine on behavioural disturbances in AD are therefore warranted.     

Accentuation effects and illusory change in exemplar-based category learning

Examined the hypothesis that information enhancing category differences receives greater weight in estimates of category means than information that reduces such differences. In the first experiment, subjects estimated the cumulative means of test scores of two groups of students. The experimental manipulation involved a gradual shift of the true mean of one group either towards or away from the true mean of the other group. As predicted, changes of estimates were larger when the two means became more dissimilar than when they became more similar. The second experiment involved otherwise identical procedures, but the variance in one category was increased while the mean remained stable. Subjects perceived an illusory change of the mean away from the comparison category. It is suggested that accentuation effects of this kind may limit the reduction of social stereotypes.     

Inhibited power motivation and persuasive communication: a lens model analysis

The authors tested the hypothesis that after motive arousal, individuals with an inhibited power motive (IPM) would excel at a persuasive task and explored the behavioral strategies IPM individuals use to that purpose. Sixty-eight participants presented their point of view on a controversial subject to another person. Power motivation and inhibition were both assessed by a picture-story test. Prior to their presentation, half of the participants imaginatively explored the ensuing task. The other half was assigned to a no-imagery control condition. Lens model analysis of videotaped presentations revealed that IPM participants in the imagery condition were judged to be the most persuasive of all participants. This interactive effect of power motivation, inhibition, and imagery condition was accounted for by three behavioral cues: verbal fluency, gesturing, and eyebrow lifts. No comparable effects emerged among no-imagery participants.