Double dissociations in visual and spatial short-term memory

A visual short-term memory task was more strongly disrupted by visual than spatial interference, and a spatial memory task was simultaneously more strongly disrupted by spatial than visual interference. This double dissociation supports a fractionation of visuospatial short-term memory into separate visual and spatial components. In 6 experiments, this interpretation could be defended against alternative explanations in terms of trade-offs in resource allocation between memory tasks and interference tasks, in terms of an involvement of short-term consolidation and long-term memory, in terms of differential phonological-loop and central-executive involvement, and in terms of similarity-based interference.     

Parametric coupling and generalized decoupling revealed by concurrent and successive isometric contractions of distal muscles

In two experiments we examined the hypothesis of transient parametric coupling during the specification of peak forces of isometric contractions produced by the left and right hand. In the first experiment participants had to produce bimanual contractions with same and different target forces as rapidly as possible in response to an auditory signal; target forces were cued visually with variable cueing intervals. At short cueing intervals reaction times were longer when different peak forces had to be specified than when same peak forces were cued, and this reaction-time difference declined as the cueing interval was increased. Independent of the cueing interval intermanual correlations of peak forces, rise times, and reaction times were smaller in conditions with different peak forces than in those with same peak forces. In the second experiment imperative signals for left-hand and right-hand contractions were separated in time. Target forces for the first response were cued with variable cueing intervals, while for the second response the cues were presented simultaneously with the second imperative signal. Reaction time of the second response was longer when target forces for the two successive responses were different rather than same, and this reaction-time difference declined when the delay of the second signal was increased as well as when the cueing interval for the first response became longer. These results are consistent with the hypothesis of a transient cross-talk between concurrent processes of peak-force specifications; in addition they indicate generalization of the decoupling required to specify different peak forces concurrently to the specification of temporal response characteristics and to processes of response initiation.     

Syntactic priming in English sentence production: categorical and latency evidence from an Internet-based study

To date, syntactic priming in sentence production has been investigated categorically, in terms of the probabilities of reusing particular syntactic structures. In this paper, we report a web-based replication of Pickering and Branigan (1998), Experiment 1, using a typed sentence completion paradigm that made it possible to record not only the responses made but also the response onset latency for each sentence completion. In conditions where priming occurred (as determined categorically), responses took less time when target completions were of the same type as preceding prime completions than when they differed. As well as validating Internet-based research by direct comparison with laboratory-based work, our findings strengthen the support for an architectural account of syntactic priming as envisaged by Pickering and Branigan.     

Temporal, but not spatial, context modulates a masked prime's effect on temporal order judgment, but not on response latency

Three experiments investigated a dissociation originally described by Neumann, Esselmann, and Klotz. Stimuli were geometric shapes, preceded by similar shapes that were masked by metacontrast. Each experiment consisted of three parts. In the reaction time (RT) part, participants saw an array of geometric shapes, one of which was marked by bars, and had to respond to the marked shape's position by pressing an appropriate button. A prime (a similar, but smaller stimulus) preceded either the marked or an unmarked stimulus. In the temporal order judgment (TOJ) part, the task was to judge the temporal order of the marked and the unmarked stimulus. In the detection part, detectability of the prime was tested. Although its detectability was zero or close to zero, the prime affected both RT and the apparent onset as measured by TOJ. The effect on RT was significantly larger than the effect on TOJ (Exp. 1). Increasing the spatial context (number of non-target stimuli in the display) did not affect this pattern (Exp. 2). By contrast, reducing the temporal context (range of stimulus onset asynchronies) abolished the prime's effect in the TOJ task, although the prime affected RT under identical conditions. It is concluded that partially different mechanisms mediate the prime's effect in the two tasks and that the effect of stimulus context on TOJ found in the Neumann et al. study was due to temporal, not spatial context. Received: 17 December 1997 / Accepted: 15 December 1998     

Method-specific variance in the implicit association test

The Implicit Association Test (IAT; A. G. Greenwald, D. E. McGhee, & J. L. K. Schwartz, 1998) can be used to assess interindividual differences in the strength of associative links between representational structures such as attitude objects and evaluations. Four experiments are reported that explore the extent of method-specific variance in the IAT. The most important findings are that conventionally scored IAT effects contain reliable interindividual differences that are method specific but independent of the measures' content, and that IAT effects can be obtained in the absence of a preexisting association between the response categories. Several techniques to decrease the impact of method-specific variance are evaluated. The best results were obtained with the D measures recently proposed by A. G. Greenwald, B. A. Nosek, and M. R. Banaji (2003).     

The brain generates its own sentence melody: a Gestalt phenomenon in speech perception

Brain processes underlying spoken language comprehension comprise auditory encoding, prosodic analysis and linguistic evaluation. Auditory encoding usually activates both hemispheres while language-specific stages are lateralized: analysis of prosodic cues are right-lateralized while linguistic evaluation is left-lateralized. Here, we investigated to what extent the absence of prosodic information influences lateralization. MEG brain-responses indicated that syntactic violations lead to early bi-lateral brain responses for syntax violations. When the pitch of sentences was flattened to diminish prosodic cues, the brain's syntax response was lateralized to the right hemisphere, indicating that the missing pitch was generated automatically by the brain when it was absent. This represents a Gestalt phenomenon, since we perceive more than is actually presented.     

A machine learning approach to infant distress calls and maternal behaviour of wild chimpanzees

Animal Cognition - Distress calls are an acoustically variable group of vocalizations ubiquitous in mammals and other animals. Their presumed function is to recruit help, but there has been much...     

Treatment effects on count outcomes with non-normal covariates

The effects of a treatment or an intervention on a count outcome are often of interest in applied research. When controlling for additional covariates, a negative binomial regression model is usually applied to estimate conditional expectations of the count outcome. The difference in conditional expectations under treatment and under control is then defined as the (conditional) treatment effect. While traditionally aggregates of these conditional treatment effects (e.g., average treatment effects) are computed by averaging over the empirical distribution, a recently proposed moment-based approach allows for computing aggregate effects as a function of distribution parameters. The moment-based approach makes it possible to control for (latent) multivariate normally distributed covariates and provides more reliable inferences under certain conditions. In this paper we propose three different ways to account for non-normally distributed continuous covariates in this approach: an alternative, known non-normal distribution; a plausible factorization of the joint distribution; and an approximation using finite Gaussian mixtures. A saturated model is used for categorical covariates, making a distributional assumption obsolete. We further extend the moment-based approach to allow for multiple treatment conditions and the computation of conditional effects for categorical covariates. An illustrative example highlighting the key features of our extension is provided.