Human odometry verifies the symmetry perspective on bipedal gaits

Bipedal gaits have been classified on the basis of the group symmetry of the minimal network of identical differential equations (alias cells) required to model them. Primary gaits are characterized by dihedral symmetry, whereas secondary gaits are characterized by a lower, cyclic symmetry. This fact was used in a test of human odometry. Results suggest that when distance is measured and reported by gaits from the same symmetry class, primary and secondary gaits are comparable. Switching symmetry classes at report compresses (primary to secondary) or inflates (secondary to primary) measured distance, with the compression and inflation equal in magnitude. Lessons are drawn from modeling the dynamics of behaviors executed in parallel (e.g., interlimb coordination) to model the dynamics of human odometry, in which the behaviors are executed sequentially. The major observations are characterized in terms of a dynamics of sequentially coupled measure and report phases, with relative velocity as an order parameter, or equilibrium state, and difference in symmetry class as an imperfection parameter, or detuning, of that dynamic.     

An optimal construction of Hanf sentences

We give a new construction of formulas in Hanf normal form that are equivalent to first-order formulas over structures of bounded degree. This is the first algorithm whose running time is shown to be elementary. The triply exponential upper bound is complemented by a matching lower bound.     

Problem solving with a simple transformation problem with and without continuous external memory support

Problem solvers can use external memory aids to represent problem information. In this study, an external problem representation was either continuously available or available on demand of the participants. Two experiments explore the hypothesis that despite the higher working memory load without a continuous external memory support, problem solvers try to reduce the cognitive costs by implementing deliberate problem solving strategies. Problem solving with and without continuous external memory support was found to be largely equivalent with high and low operator implementation costs and in problem spaces of different sizes.     

Attentional bias towards angry faces is moderated by the activation of a social processing mode in the general population

ABSTRACT

Dot-probe studies usually find an attentional bias towards threatening stimuli only in anxious participants, but not in non-anxious participants. In the present study, we conducted two experiments to investigate whether attentional bias towards angry faces in unselected samples is moderated by the extent to which the current task requires social processing. In Experiment 1, participants performed a dot-probe task involving classification of either socially meaningful targets (schematic faces) or meaningless targets (scrambled schematic faces). Targets were preceded by two photographic face cues, one angry and one neutral. Angry face cues only produced significant cueing scores (i.e. faster target responses if the target replaced the angry face compared to the neutral face) with socially meaningful targets, not with meaningless targets. In Experiment 2, participants classified only meaningful targets, which were either socially meaningful (schematic faces) or not (schematic houses). Again, mean cueing scores were significantly moderated by the social character of the targets. However, cueing scores in this experiment were non-significant in the social target condition and significantly negative in the non-social target condition. These results suggest that attentional bias towards angry faces in the dot-probe task is moderated by the activation of a social processing mode in unselected samples.     

Affective priming in the valent/neutral categorisation task is due to affective matching,not encoding facilitation: Reply to Spruyt

Spruyt obtained an affective congruency effect in a valent/neutral categorisation task, which contrasts with the absence of such an effect in the same task that was reported by Werner and Rothermund. The crucial difference between the two studies is that Spruyt presented only valent primes, whereas Werner and Rothermund presented equal amounts of valent and neutral primes and targets in their experiments. Removing the neutral primes introduces a confound of affective matches with the required response. Affective congruency effects in Spruyt's study can be explained straightforwardly in terms of such an affective matching strategy. To demonstrate the influence of matching strategies in the valent/neutral task without neutral primes, we conducted an experiment in which we induced an affective mismatching strategy. In support of our reasoning, this study revealed an affective incongruency effect in the valent/neutral categorisation task. We conclude that affective congruency as well as incongruency effects in the valent/neutral categorisation task reflect post-lexical affective (mis-)matching strategies rather than encoding facilitation.     

Intact emotion-induced recognition bias in neuropsychological patients with executive control deficits

In recognition memory tasks, emotionally negative words are judged more often as "old" relative to emotionally neutral words, suggesting a shift in response bias. We wondered whether this bias shift was due to the flexible regulation of executive control during memory retrieval. To address this question, we investigated individuals with high variability in executive control functions. As expected, we observed that emotional word meaning did indeed have a strong influence on the bias toward responding "old," independent of recognition accuracy and overall response bias. However, these effects were uncorrelated with executive control, as measured by the Trail Making Test, and were fully intact, even in a sample of hospitalized neurological patients with severe executive dysfunctions, some of whom had marked damage in fronto-thalamo-striatal networks. Having concluded that the emotion-induced bias must develop on different grounds, we went on to discuss alternative explanations.     

Using saccade tasks as a tool to analyze executive dysfunctions in schizophrenia

Executive dysfunctions can be frequently observed in schizophrenia. They are more persistent than psychotic symptoms and are assumed to contribute to a variety of clinical signs of the disease. However, the cognitive mechanisms underlying dysexecutive behaviors are not yet understood. The aim of this article is to demonstrate how saccade tasks can be used to analyze the mechanisms involved in the dysexecutive syndrome of schizophrenic patients. There are numerous reports showing that schizophrenic patients make many unwanted reflexive saccades in the antisaccade task. These errors are usually explained by an impairment of a distinct inhibitory mechanism. However, unwanted reflexive saccades may also be secondary to a more fundamental deficit in activating goal-directed behavior. Recent theoretical and empirical approaches to this issue are reviewed and discussed. An integrative view of deficits in inhibition, goal-directed behavior, and working memory in schizophrenic patients is proposed.     

Effects of cuing on short-term retention of order information

In two experiments, subjects recalled one of two letter sequences following a digit-filled retention interval. Recall performance was increased by precues informing subjects which letter sequence would be tested, and the cuing advantage remained throughout 60-digit retention intervals. No improvement was found, however, for cues occurring after the letters but before the digits. The cuing effects were attributed to encoding, not rehearsal, processes and were explained by a version of the Estes perturbation model, which included a long-term storage component and a fixed perturbation probability.     

Effects of orienting tasks on sentence comprehension and cued recall

In three experiments, cued recall of sentences was found to vary with the type of orienting task performed during sentence presentation. Retrieval cues referred to information probably inferred from the sentences. Each of the semantic tasks led to greater recall than did the nonsernantic task; this task effect occurred in a between-subjects design and in a within-subjects design. Furthermore, the use of a task-indicating signal after each sentence, in the within-subjects design, allowed the manipulation of the timing and type of orienting task. The task effect on recall appeared even with a delay of the task-indicating signal and/or the addition of an initial semantic task (performed prior to the indicated task). The findings suggest both a processing explanation and an interruption explanation of task effects.