Perceiving while acting: action affects perception

In two experiments we studied how motor responses affect stimulus encoding when stimuli and responses are functionally unrelated and merely overlap in time. Such R-S effects across S-R assignments have been reported by Schubö, Aschersleben, and Prinz (2001), who found that stimulus encoding was affected by concurrent response execution in the sense of a contrast (i.e., emphasizing differences). The present study aimed at elucidating the mechanisms underlying this effect. Experiment 1 studied the time course of the R-S effect. Contrast was only obtained for short intertrial intervals (ITIs). With long ITIs contrast turned into assimilation (i.e., emphasizing similarities). Experiment 2 excluded an interpretation of the assimilation effect in terms of motor repetition. Our findings support the notion of a shared representational domain for perception and action control, and suggest that contrast between stimulus and response codes emerges when two S-R assignments compete with each other in perception. When perceptual competition is over, assimilation emerges in memory.     

Object permanence in common marmosets (Callithrix jacchus)

A series of 9 search tasks corresponding to the Piagetian Stages 3-6 of object permanence were administered to 11 common marmosets (Callithrix jacchus). Success rates varied strongly among tasks and marmosets, but the performances of most subjects were above chance level on the majority of tasks of visible and invisible displacements. Although up to 24 trials were administered in the tests, subjects did not improve their performance across trials. Errors were due to preferences for specific locations or boxes, simple search strategies, and attentional deficits. The performances of at least 2 subjects that achieved very high scores up to the successive invisible displacement task suggest that this species is able to represent the existence and the movements of unperceived objects.     

Association of serotonin transporter promoter gene polymorphism with violence: relation with personality disorders, impulsivity, and childhood ADHD psychopathology

There is evidence that disturbances in central serotonin (5-HT) function have a role in impulsive aggression, violence, and criminality. A deletion/insertion polymorphism within the 5-HT transporter (5-HTT) promoter gene (5-HTT gene-linked polymorphic region, 5-HTTLPR) is thought to be associated with several psychopathological phenotypes related to disturbed impulse control, anxiety and depression. This study examined the association of the 5-HTTLPR with violent behavior in a sample of 153 male Caucasians referred for a forensic psychiatric examination. We found a significant excess of the short (s) allele and the s/s genotype in patients characterized by recurrent and overt physical violent behavior. This genetic variance explained 5% of the variance of violent behavior. When controlled for the impact of several psychopathologies related to violent behavior, this association was observed in individuals with a history of childhood attention deficit/hyperactivity disorder (ADHD)-related symptoms, but not presenting with personality disorder or increased impulsiveness. In conclusion, the results (i). suggest an association between serotonergic dysfunction and violent behavior, (ii). provide evidence for an-at least partial-genetic regulation of violent behavior in a subgroup of male offenders, and (iii). suggest a significant role for 5-HT transporter functionality for violent behavior.     

DRG-Vergütung und Kosten stationärer integrierter psychosomatischer Behandlung

Ohne ZusammenfassungDie Autoren M. Rose und R. Lohmann zeichnen für den Beitrag als gleichberechtigte Erstautoren.     

Representing others' actions: just like one's own?

Previous research has shown that observing others' actions can affect individual performance of the same actions. In the present study, we developed a new paradigm to investigate whether and how complementary actions at the disposal of another agent are represented and influence one's own actions. A spatial compatibility task was distributed among two people so that each participant took care of one of two responses. The identical task was performed alone and alongside another participant. There was a spatial compatibility effect in the group setting only. It was similar to the effect obtained when one person took care of both responses. This result suggests that one's own actions and others' actions are represented in a functionally equivalent way.     

Pigeons use item-specific and category-level information in the identification and categorization of human faces

Three experiments examined the pigeon's ability to adapt to the specific tasks of identification and categorization of complex visual stimuli by attending to information at different levels of abstraction. In Experiment 1, pigeons were successively trained to discriminate first between pairs of human faces from the same sex and then between male and female faces. A final test revealed that the associations formed in the first training phase did not survive categorization training, indicating that the pigeons used item-specific information to discriminate faces of the same sex, but shifted their attention to category-level information for discriminating between the male and female categories. Two further experiments disproved alternative explanations. The results support the feature-learning account of open-ended categorization in animals.     

On the relative speed account of number-size interference in comparative judgments of numerals

Humans show systematic congruency effects due to irrelevant variations of the numerical value or the physical size of digits in judgments about either of these 2 attributes alone. According to influential models (e.g., J. Tzelgov, J. Meyer, & A. Henik, 1992), these effects are characterized by genuine asymmetries of size and number processing not accounted for by simple relative speed considerations, whereas some recent work (e.g., A. Pansky & D. Algom, 1999) partly challenges this view. This article presents 2 qualitative gradient-based predictions made by relative speed models and a diffusion-based implementation of the relative speed view to quantitatively account for response times and error rates in comparative judgments of digits. The results of 2 experiments using a completely task-symmetric design are in accord with these detailed predictions; they are also consistent with the view that both number and size are converted into magnitude representations of similar structure.     

Off-line authorship effects in action perception

Does the perception of our actions differ from the perception of other individuals' actions when we observe them, like other individual's actions, in an offline perspective? Previous studies, using recognition as well as prediction judgments, suggest that it does even if the stimulus information is reduced to a single moving point-light. Here, we assessed whether this difference also affects the timing of actions. This was tested in two experiments, using a specific synchronization task. After some practice, self-generated action events were anticipated faster than other action events, provided that the anticipation could not be accomplished sufficiently well on the basis of easily detectable cues. The results are discussed with regard to the previous findings of off-line authorship effects in action perception.     

The early origins of goal attribution in infancy

We contrast two positions concerning the initial domain of actions that infants interpret as goal-directed. The 'narrow scope' view holds that goal-attribution in 6- and 9-month-olds is restricted to highly familiar actions (such as grasping). The cue-based approach of the infant's 'teleological stance', however, predicts that if the cues of equifinal variation of action and a salient action effect are present, young infants can attribute goals to a 'wide scope' of entities including unfamiliar human actions and actions of novel objects lacking human features. It is argued that previous failures to show goal-attribution to unfamiliar actions were due to the absence of these cues. We report a modified replication of Woodward (1999) showing that when a salient action-effect is presented, even young infants can attribute a goal to an unfamiliar manual action. This study together with other recent experiments reviewed support the 'wide scope' approach indicating that if the cues of goal-directedness are present even 6-month-olds attribute goals to unfamiliar actions.     

Therapeutic versus genuine cloning: what are the real moral issues?

In order to answer the question raised in the title of my paper, I first put forward a general ethical theory, which is based on the traditional maxim neminem laedere. Second, I show how this principle in conjunction with certain assumptions concerning the value of life entails certain fundamental bioethical principles. Thus killing a living being Y is morally wrong whenever the intrinsic value of the life that Y would otherwise live is positive. But procreating a living being Y is prima facie (i.e., with regard to the interests of Y) morally neutral, i.e. neither bad nor good. Third I will argue that the question of moral rights should always be reduced to the question of the morality of certain corresponding actions. In particular, granting Y a right to life should be taken to mean that it would be morally wrong if someone else were to put an end to Y's life. In a similar vein, I suggest answers to some other questions of the reproductive rights issue. Fourth, with respect to the controversial issue of genuine cloning, I do not see any compelling moral reasons against this utopian way of procreating full-grown individuals. Nevertheless, I think there are a lot of other good (pragmatic, rational) reasons not to try to produce a human Dolly. Finally, as regards the use or abuse of human embryos as potential suppliers of stem-cells for the cure of other people's diseases, it seems morally safe to perform experiments at least with those embryos which, like spare embryos that remained from measures of in vitro fertilization, would not have a life anyway. It's more difficult to decide, however, whether it would be morally safe to produce embryos (for instance through cloning) only for the sake of using them in the aforementioned way.