Mining event-related brain dynamics

This article provides a new, more comprehensive view of event-related brain dynamics founded on an information-based approach to modeling electroencephalographic (EEG) dynamics. Most EEG research focuses either on peaks 'evoked' in average event-related potentials (ERPs) or on changes 'induced' in the EEG power spectrum by experimental events. Although these measures are nearly complementary, they do not fully model the event-related dynamics in the data, and cannot isolate the signals of the contributing cortical areas. We propose that many ERPs and other EEG features are better viewed as time/frequency perturbations of underlying field potential processes. The new approach combines independent component analysis (ICA), time/frequency analysis, and trial-by-trial visualization that measures EEG source dynamics without requiring an explicit head model.     

Validated intraclass correlation statistics to test item performance models

A new method, with an application program in Matlab code, is proposed for testing item performance models on empirical databases. This method uses data intraclass correlation statistics as expected correlations to which one compares simple functions of correlations between model predictions and observed item performance. The method rests on a data population model whose validity for the considered data is suitably tested and has been verified for three behavioural measure databases. Contrarily to usual model selection criteria, this method provides an effective way of testing under-fitting and over-fitting, answering the usually neglected question "does this model suitably account for these data?"     

On the representational systems underlying prospection: Evidence from the event-cueing paradigm

The ability to think about the future-prospection-is central to many aspects of human cognition and behavior, from planning and decision making, to self-control and the construction of a sense of identity. Yet, the exact nature of the representational systems underlying prospection is not fully understood. Recent findings point to the critical role of episodic memory in imagining specific future events, but it is unlikely that prospection depends solely on this system. Using an event-cueing paradigm in two studies, we here show that specific events that people imagine might happen in their personal future are commonly embedded in broader event sequences-termed event clusters-that link a set of envisioned events according to causal and thematic relations. These findings provide novel evidence that prospection relies on multiple representational systems, with general autobiographical knowledge structures providing a frame that organizes imagined events in overarching event sequences. The results further suggest that knowledge about personal goals plays an important role in structuring these event sequences, especially for the distant future.     

Simulating individual word identification thresholds and errors in the fragmentation task

This article presents a large-scale study that collected word identification thresholds and errors in the fragmentation task for all four-letter French words. In the first part of this article, we identify some of the variables (e.g., word frequency, neighborhood size, letter confusability) that affect performance in the fragmentation task. In the second part, we analyze individual response performance and identify different response strategies. We demonstrate that the interactive activation model can account for individual response strategies by adapting two of its original parameters: word-letter feedback and letter-word inhibition. In the third part, we demonstrate that the adaptation of the interactive activation model to the fragmentation task makes it possible to successfully simulate a facilitatory frequency effect on identification thresholds, an inhibitory neighborhood size effect on error rates, and an inhibitory letter confusability effect on identification thresholds. When the task-specific processes of the fragmentation task are specified and individual response strategies are considered, the interactive activation model provides a parsimonious architecture for modeling the task-independent processes involved in word perception.     

Lateralization in haptic processing: An apparatus for analyzing manual strategies

We describe an apparatus for testing laterality in haptic processing in the discrimination of nonsense shapes in humans or monkeys. The system, which permits either mono- or dichhaptic discrimination, automatically provides data on the measurement of accuracy along with information on hand exploratory strategies.     

The effects of intention and practice on a non-motor duration estimation task

It has already been shown that the intention to reproduce a motor task in the future improves its learning. Here, we tested whether intention had a similar effect on learning to perform a non-motor duration estimation task, and if intention interacted with the amount of practice. Participants learned to estimate and compare two different durations, with or without intending to reproduce this learning in the future, and with two different amounts of practice. The results showed that intention and practice enhanced task learning independently. Moreover, only practice enhanced learning in over-estimation strategy. These finding are discussed with respect to a possible mechanism by which intention and practice might improve the learning of a duration task.     

Improving accuracy in detecting acoustic onsets

In current cognitive psychology, naming latencies are commonly measured by electronic voice keys that detect when sound exceeds a certain amplitude threshold. However, recent research (e.g., K. Rastle & M. H. Davis, 2002) has shown that these devices are particularly inaccurate in precisely detecting acoustic onsets. In this article, the authors discuss the various problems and solutions that have been put forward with respect to this issue and show that classical voice keys may trigger several tens of milliseconds later than acoustic onset. The authors argue that a solution to this problem may come from voice keys that use a combination of analogue and digital noise (nonspeech sound) detection. It is shown that the acoustic onsets detected by such a device are only a few milliseconds delayed and correlate highly (up to .99) with reaction time values obtained by visual waveform inspection.     

The Hebb repetition effect as a laboratory analogue of novel word learning

The present study tests the hypothesis that a common ordering mechanism underlies both short-term serial recall of verbal materials and the acquisition of novel long-term lexical representations, using the Hebb repetition effect. In the first experiment, participants recalled visually presented nonsense syllables following a typical Hebb effect learning protocol. Replicating the Hebb repetition effect, we observed improved recall for repeated sequences of syllables. In the second experiment, the same participants performed an auditory lexical decision task, which included nonwords that were constructed from the syllables used in the first experiment. We observed inhibited rejection of nonwords that were composed of the repeated Hebb sequences, compared to nonwords that were built from nonrepeated filler sequences. This suggests that a long-term phonological lexical representation developed during Hebb learning. Accordingly, the relation between immediate serial recall and word learning is made explicit by arguing that the Hebb repetition effect is a laboratory analogue of naturalistic vocabulary acquisition.     

Item performance in visual word recognition

Standard factorial designs in psycholinguistics have been complemented recently by large-scale databases providing empirical constraints at the level of item performance. At the same time, the development of precise computational architectures has led modelers to compare item-level performance with item-level predictions. It has been suggested, however, that item performance includes a large amount of undesirable error variance that should be quantified to determine the amount of reproducible variance that models should account for. In the present study, we provide a simple and tractable statistical analysis of this issue. We also report practical solutions for estimating the amount of reproducible variance for any database that conforms to the additive decomposition of the variance. A new empirical database consisting of the word identification times of 140 participants on 120 words is then used to test these practical solutions. Finally, we show that increases in the amount of reproducible variance are accompanied by the detection of new sources of variance.     

Cognitive control of sequential knowledge in 2-year-olds: evidence from an incidental sequence-learning and -generation task

Under incidental instructions, thirty-eight 2-year-olds were trained on a six-element deterministic sequence of spatial locations. Following training, subjects were informed of the presence of a sequence and asked to either reproduce or suppress the learned material. Children's production of the trained sequence was modulated by these instructions. When asked to suppress the trained sequence, the children were able to increase generation of paths that were not from the training sequence. Their performance was thus dependent on active suppression of knowledge, rather than on a random generation strategy. This degree of control in 2-year-olds stands in stark contrast to 3-year-olds' failure to control explicitly instructed rule-based knowledge (as measured by the dimensional-change card-sort task). We suggest that the incidental nature of a learning episode enables the acquisition of a more procedural form of knowledge with which this age group has more experience prior to the onset of fluent language.