Arthur M. Jacobs

ORTHOGRAPHIC PROCESSING IN VISUAL WORD RECOGNITION : A MULTIPLE READ-OUT MODEL

A model of orthographic processing is described that postulates read-out from different information dimensions, determined by variable response criteria set on these dimensions. Performance in a perceptual identification task is simulated as the percentage of trials on which a noisy criterion set on the dimension of single word detector activity is reached. Two additional criteria set on the dimensions of total lexical activity and time from stimulus onset are hypothesized to be operational in the lexical decision task. These additional criteria flexibly adjust to changes in stimulus material and task demands, thus accounting for strategic influences on performance in this task. The model unifies results obtained in response-limited and data-limited paradigms and helps resolve a number of inconsistencies in the experimental literature that cannot be accommodated by other current models of visual word recognition.

Models of visual word recognition: Sampling the state of the art

A chart of models of visual word recognition is presented that facilitates formal comparisons between models of different formats. In the light of the theoretical contributions to this special section, sets of criteria for the evaluation of models are discussed, as well as strategies for model construction.

The physiological origin of task-evoked systemic artefacts in functional near infrared spectroscopy.

A major methodological challenge of functional near-infrared spectroscopy (fNIRS) is its high sensitivity to haemodynamic fluctuations in the scalp. Superficial fluctuations contribute on the one hand to the physiological noise of fNIRS, impairing the signal-to-noise ratio, and may on the other hand be erroneously attributed to cerebral changes, leading to false positives in fNIRS experiments. Here we explore the localisation, time course and physiological origin of task-evoked superficial signals in fNIRS and present a method to separate them from cortical signals. We used complementary fNIRS, fMRI, MR-angiography and peripheral physiological measurements (blood pressure, heart rate, skin conductance and skin blood flow) to study activation in the frontal lobe during a continuous performance task. The General Linear Model (GLM) was applied to analyse the fNIRS data, which included an additional predictor to account for systemic changes in the skin. We found that skin blood volume strongly depends on the cognitive state and that sources of task-evoked systemic signals in fNIRS are co-localized with veins draining the scalp. Task-evoked superficial artefacts were mainly observed in concentration changes of oxygenated haemoglobin and could be effectively separated from cerebral signals by GLM analysis. Based on temporal correlation of fNIRS and fMRI signals with peripheral physiological measurements we conclude that the physiological origin of the systemic artefact is a task-evoked sympathetic arterial vasoconstriction followed by a decrease in venous volume. Since changes in sympathetic outflow accompany almost any cognitive and emotional process, we expect scalp vessel artefacts to be present in a wide range of fNIRS settings used in neurocognitive research. Therefore a careful separation of fNIRS signals originating from activated brain and from scalp is a necessary precondition for unbiased fNIRS brain activation maps.

The Berlin Affective Word List Reloaded (BAWL-R).

The study presented here provides researchers with a revised list of affective German words, the Berlin Affective Word List Reloaded (BAWL-R). This work is an extension of the previously published BAWL (Võ, Jacobs, & Conrad, 2006), which has enabled researchers to investigate affective word processing with highly controlled stimulus material. The lack of arousal ratings, however, necessitated a revised version of the BAWL. We therefore present the BAWL-R, which is the first list that not only contains a large set of psycholinguistic indexes known to influence word processing, but also features ratings regarding emotional arousal, in addition to emotional valence and imageability. The BAWL-R is intended to help researchers create stimulus material for a wide range of experiments dealing with the affective processing of German verbal material.

On the role of competing word units in visual word recognition: The neighborhood frequency effect

Psychologie Expérimentale, 28 rue Serpente, 75006 Paris, France. Current models of word recognition generally assume that word units orthographically similar to a stimulus word are involved in the visual recognition of this word. We refer to this set of orthographically similar words as an orthographic neighborhood. Two experiments are presented that investigate the ways in which the composition of this neighborhood can affect word recognition. The data indicate that the presence in the neighborhood of at least one unit of higher frequency than the stimulus word itself results in interference in stimulus word processing. Lexical decision latencies (Experiment 1) and gaze durations (Experiment 2) to words with one neighbor of higher frequency were significantly longer than to words without a more frequent neighbor.

What is the pronunciation for -ough and the spelling for /u/? A database for computing feedforward and feedback consistency in English

Recent studies suggest that performance attendant on visual word perception is affected not only by feedforward inconsistency (i.e., multiple ways to pronounce a spelling) but also by feedback inconsistency (i.e., multiple ways to spell a pronunciation). In the present study, we provide a statistical analysis of these types of inconsistency for all monosyllabic English words. This database can be used as a tool for controlling, selecting, and constructing stimulus materials for psycholinguistic and neuropsychological research. Such large-scale statistical analyses are necessary devices for developing metrics of inconsistency, for generating hypotheses for psycholinguistic experiments, and for building models of word perception, speech perception, and spelling.

Incidental effects of emotional valence in single word processing: An fMRI study

The present study aimed at identifying the neural responses associated with the incidental processing of the emotional valence of single words using event-related functional magnetic resonance imaging (fMRI). Twenty right-handed participants performed a visual lexical decision task, discriminating between nouns and orthographically and phonologically legal nonwords. Positive, neutral and negative word categories were matched for frequency, number and frequency of orthographic neighbors, number of letters and imageability. Response times and accuracy data differed significantly between positive and neutral, and positive and negative words respectively, thus, replicating the findings of a pilot study. Words showed distributed, mainly left hemisphere activations, indicating involvement of a neural network responsible for semantic word knowledge. The neuroimaging data further revealed areas in left orbitofrontal gyrus and bilateral inferior frontal gyrus with greater activation to emotional than to neutral words. These brain regions are known to be involved in processing semantic and emotional information. Furthermore, distinct activations associated with positive words were observed in bilateral middle temporal and superior frontal gyrus, known to support semantic retrieval, and a distributed network, namely anterior and posterior cingulate gyrus, lingual gyrus and hippocampus when comparing positive and negative words. The latter areas were previously associated with explicit and not incidental processing of the emotional meaning of words and emotional memory retrieval. Thus, the results are discussed in relation to models of processing semantic and episodic emotional information.

Eye movement control during reading: II. Frequency of refixating a word.

An analysis of over 40,000 eye fixations made by college students during reading indicates that the frequency of immediately refixating a word following an initial eye fixation on it varies with the location ofthat fixation. The refixation frequency is lowest near the center of the word, posi-tively accelerating with distance from the center. The data are well fit by a parabolic function. Assuming that refixation frequency is related to the frequency of successful word identification, the observed curvilinear relation results naturally from models that postulate a linear decrease in visual information with retinal eccentricity. A single letter difference in fixation location in a word can make a sizeable difference in the likelihood of refixating that word. The effects of word length and cultural frequency on the frequency of refixating are also examined.

Coregistration of eye movements and EEG in natural reading analyses and review

Brain-electric correlates of reading have traditionally been studied with word-by-word presentation, a condition that eliminates important aspects of the normal reading process and precludes direct comparisons between neural activity and oculomotor behavior. In the present study, we investigated effects of word predictability on eye movements (EM) and fixation-related brain potentials (FRPs) during natural sentence reading. Electroencephalogram (EEG) and EM (via video-based eye tracking) were recorded simultaneously while subjects read heterogeneous German sentences, moving their eyes freely over the text. FRPs were time-locked to first-pass reading fixations and analyzed according to the cloze probability of the currently fixated word. We replicated robust effects of word predictability on EMs and the N400 component in FRPs. The data were then used to model the relation among fixation duration, gaze duration, and N400 amplitude, and to trace the time course of EEG effects relative to effects in EM behavior. In an extended Methodological Discussion section, we review 4 technical and data-analytical problems that need to be addressed when FRPs are recorded in free-viewing situations (such as reading, visual search, or scene perception) and propose solutions. Results suggest that EEG recordings during normal vision are feasible and useful to consolidate findings from EEG and eye-tracking studies.

Testing a semistochastic variant of the interactive activation model in different word recognition experiments

A semistochastic variant of the interactive activation (IA) model of context effects in letter perception (McClelland & Rumelhart, 1981) was used to simulate response time distributions and means in different experiments investigating the effects of word frequency, neighborhood size and frequency, and orthographic priming in visual word recognition. The results provide evidence in favor of the connectivity assumption underlying the model but question the necessity of the interactivity assumption for simulating latencies in word recognition tasks. Together with those of a recent study by McClelland (1991), the present results suggest that 10 years after its appearance, the IA models potential for testing hypotheses about the structure and dynamics of basic phenomena of human information processing in a variety of perceptual and cognitive tasks is not yet fully exploited.