A model of working memory capacity in the radial-arm maze task

The radial arm maze is one of the most commonly used tests for assessing working memory in laboratory animals. However, to date, there exists no quantitative method of estimating working memory capacity from performance on this task. Here, we present a mathematical model of performance on the radial arm maze from which we can derive estimates of capacity. We derive explicit results for the two most commonly used measures of performance as functions of number of arms in the maze and memory capacity, assuming a uniform random search. We simulate random non-uniform search strategies. Comparing our model to previous experiments, we show that our model predicts a working memory capacity in the range of 3-9 at the level of performance observed in these experiments. This estimate is within the typical estimate of human working memory capacity. Performance of rats on large mazes (e.g. 48 arms) has been used as evidence that the working memory capacity of rats may be significantly larger than that of humans. We report that memory capacity in the range 3-9 is sufficient to explain the performance of rats in very large radial mazes. Furthermore, when we simulate non-uniform random search strategies observed in the experiments, the resulting estimates do not differ significantly from those assuming a uniform random search. We conclude that a list-based model of working memory with modest capacity is more powerful than previously expected.     

Top-down influences on attentional capture by color changes

Previous studies have shown that a change in an existing object is not as effective in capturing attention as the appearance of a new object. This view was recently challenged by Lu and Zhou (Psychonomic Bulletin and Review 12:567–572, 2005), who found strong capture effects for an object changing its color. We suspected that this finding critically depends on a procedural particularity in Lu and Zhou’s study, namely that the color of the unique item and the color of the no-unique items randomly switched between trials. In the current study we replicate Lu and Zhou’s capture effect (Experiment 1) and show that no capture occurs when the color-to-stimuli assignment is fixed (Experiment 2). Two further experiments suggest that the capture effect in Experiment 1 is not because the unique item switched color (Experiment 3), but because all the no-unique items switched color (Experiment 4). The results are discussed considering top-down modulation and inter-trial priming effects.

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PRP-paradigm provides evidence for a perceptual origin of the negative compatibility effect

Visual stimuli (primes) that are made invisible by masking can affect motor responses to a subsequent target stimulus. When a prime is followed by a mask which is followed by a target stimulus, an inverse priming effect (or negative compatibility effect) has been found: Responses are slow and frequently incorrect when prime and target stimuli are congruent, but fast and accurate when prime and target stimuli are incongruent. To functionally localize the origins of inverse priming effects, we applied the psychological refractory period (PRP-) paradigm which distinguishes a perceptual level, a central bottleneck, and a level of motor execution. Two dual-task experiments were run with the PRP-paradigm to localize the inverse priming effect relative to the central bottleneck. Together, results of the Effect-Absorption and the Effect-Propagation Procedure suggest that inverse priming effects are generated by perceptual mechanisms. We suggest two perceptual mechanisms as the source of inverse priming effects.     

Fractal Images of Formal Systems

Formal systems are standardly envisaged in terms of a grammar specifying well-formed formulae together with a set of axioms and rules. Derivations are ordered lists of formulae each of which is either an axiom or is generated from earlier items on the list by means of the rules of the system; the theorems of a formal system are simply those formulae for which there are derivations. Here we outline a set of alternative and explicitly visual ways of envisaging and analyzing at least simple formal systems using fractal patterns of infinite depth. Progressively deeper dimensions of such a fractal can be used to map increasingly complex wffs or increasingly complex value spaces, with tautologies, contradictions, and various forms of contingency coded in terms of color. This and related approaches, it turns out, offer not only visually immediate and geometrically intriguing representations of formal systems as a whole but also promising formal links (1) between standard systems and classical patterns in fractal geometry, (2) between quite different kinds of value spaces in classical and infinite-valued logics, and (3) between cellular automata and logic. It is hoped that pattern analysis of this kind may open possibilities for a geometrical approach to further questions within logic and metalogic.\looseness=-1     

Independence of serial position and response conflict in pre-planned manual response sequences

The present study investigates the effect of spatial stimulus–response correspondence (i.e. Simon effect) in pre-planned manual response sequences. Participants performed pre-cued response sequences consisting of three (Experiment 1) or four (Experiments 2 and 3) key-presses at different locations. Importantly, participants performed each response to a visual go signal, which appeared at a location corresponding to one response in the sequence. This task allowed investigating interference gradients across spatially noncorresponding conditions. We observed a Simon effect at each serial position, that is, RT for the corresponding condition was always shorter than RT for each noncorresponding condition. However, we failed to observe interference gradients from both preceding and subsequent responses in the sequence. These results are inconsistent with (1) a primacy gradient of activations representing serial order and (2) the temporary suppression of an executed response as a mechanism for preventing response repetitions. However, results provide indirect evidence for positional models of serial order.     

Acceptance of sexual aggression myths in a representative sample of German residents

A representative sample of German residents (N = 5397) was surveyed with the aim of studying their acceptance of contemporary rape myths (RMA), using items from the Acceptance of Modern Myths About Sexual Aggression Scale [AMMSA; Gerger et al., 2007] in relation to demographic variables (e.g., gender, age), intolerant belief systems (e.g., sexism, islamophobia), the ideologies of rightwing authoritarianism (RWA), and social dominance orientation (SDO), as well as gender identification. Age showed a U-shaped relationship with RMA, whereas gender was unrelated to RMA. For men (women), greater identification with their gender was associated with higher (lower) RMA. Substantial correlations of RMA with intolerant belief systems support the idea of a schema of intolerance. Although RWA and SDO were both related to RMA, only RWA explained unique variance beyond the effects of intolerant belief systems. Results are discussed in comparison to prior studies using mainly student samples.     

Observation and physical practice: coding of simple motor sequences

An experiment was conducted to determine the coordinate system used in the development of movement codes during observation and utilized on later physical practice performance of a simple spatial-temporal movement sequence. The task was to reproduce a 1.3-s spatial-temporal pattern of elbow flexions and extensions. An intermanual transfer paradigm with a retention test and two transfer tests was used: a mirror transfer test where the same pattern of muscle activation and limb joint angles was required and a nonmirror transfer test where the visual-spatial pattern of the sequence was reinstated on the transfer test. The results indicated a strong advantage for participants in the physical practice condition when transferred to the mirror condition in which the motor coordinates (e.g., pattern of muscle activation and joint angles) were reinstated relative to transfer performance when the visual-spatial coordinates were reinstated (visual and spatial location of the target waveform). The observation group, however, demonstrated an advantage when the visual-spatial coordinates were reinstated. These results demonstrate that codes based in motor coordinates can be developed relatively quickly for simple rapid movement sequences when participants are provided physical practice, but observational practice limits the system to the development of codes based in visual-spatial coordinates. Performances of control participants, who were not permitted to practise or observe the task, were quite poor on all tests.     

Beyond procedure's content: the role of accessibility experiences and personal uncertainty in procedural justice judgements

Procedural justice concerns play a critical role in economic settings, politics, and other domains of human life. Despite the vast evidence corroborating their relevance, considerably less is known about how procedural justice judgments are formed. Whereas earlier theorizing focused on the systematic integration of content information, the present contribution provides a new perspective on the formation of justice judgments by examining the influence of accessibility experiences. Specifically, we hypothesize that procedural justice judgments may be formed based on the ease or difficulty with which justice-relevant information comes to mind. Three experiments corroborate this prediction in that procedures were evaluated less positively when the retrieval of associated unfair aspects was easy compared to difficult. Presumably this is because when it feels easy (difficult) to retrieve unfair aspects, these are perceived as frequent (infrequent), and hence the procedure as unjust (just). In addition to demonstrating that ease-of-retrieval may influence justice judgments, the studies further revealed that reliance on accessibility experiences is high in conditions of personal certainty. We suggest that this is because personal uncertainty fosters systematic processing of content information, whereas personal certainty may invite less taxing judgmental strategies such as reliance on ease-of-retrieval.     

The role of expectation and probabilistic learning in auditory boundary perception: a model comparison

Grouping and boundary perception are central to many aspects of sensory processing in cognition. We present a comparative study of recently published computational models of boundary perception in music. In doing so, we make three contributions. First, we hypothesise a relationship between expectation and grouping in auditory perception, and introduce a novel information-theoretic model of perceptual segmentation to test the hypothesis. Although we apply the model to musical melody, it is applicable in principle to sequential grouping in other areas of cognition. Second, we address a methodological consideration in the analysis of ambiguous stimuli that produce different percepts between individuals. We propose and demonstrate a solution to this problem, based on clustering of participants prior to analysis. Third, we conduct the first comparative analysis of probabilistic-learning and rule-based models of perceptual grouping in music. In spite of having only unsupervised exposure to music, the model performs comparably to rule-based models based on expert musical knowledge, supporting a role for probabilistic learning in perceptual segmentation of music.     

Psychoanalytisch-orientierte Fokaltherapie der Depression bei Krebskranken

Emotional distress connected to a cancer disease may result in comorbid mental and especially depressive disorders. Although psychodynamic therapy is one of the most frequently applied forms of psychotherapy of depression in cancer patients there is a lack of empirical studies which meet the criteria of evidence-based psychotherapy research. This is especially true with regard to randomized controlled trials of psychodynamic psychotherapy. As far as we know no manual for psychodynamic treatment of cancer patients has yet been published. In this article a manual for a 20-session short-term psychodynamic treatment is presented. The treatment is based on Luborsky’s supportive-expressive (SE) therapy. The SE treatment manual of depressions in cancer patients presented here is an adaptation of the general SET manual as well as the SE manual for depression. In the first part the general principles of SE therapy are presented. In the second part a manual specifically adapted to the treatment of depressive cancer patients is described. The treatment manual is presently being used in a large-scale randomized controlled multi-centered study comparing short-term psychodynamic psychotherapy and treatment as usual.