No abstract

Most EEG studies analysing speech production with event related brain potential (ERP) have adopted silent metalinguistic tasks or delayed or tacit picture naming in order to avoid possible artefacts during motor preparation. A central issue in the interpretation of these results is whether the processes involved in those tasks are comparable to those involved in overt speech production. In the present study we addressed a methodological issue about the integration of stimulus-aligned and response-aligned ERPs in immediate overt picture naming in comparison to delayed production, coupled with a theoretical point on the effect of word Age of Acquisition (AoA). High density EEG recordings were used and waveform analyses and spatio-temporal segmentation were combined on stimulus-aligned and response-aligned ERPs. The same sequence and duration of topographic maps appeared in the immediate and delayed production until around 350 ms after picture onset, revealing similar encoding processes until the beginning of phonological encoding, but modulations linked to word AoA were only observed in the immediate production. Considering stimulus-aligned and responsealigned ERPs together allowed to identify that a stable topography starting around 350 ms lasts 30 ms longer for late-acquired than for early-acquired words. This difference falls within the time-window of phonological encoding and its modulation can be linked to the longer production latencies for late-acquired words.3

Selecting items for designing psycholinguistic experiments can be a very hard and time-consuming process, because of the large number of variables that need to be controlled for. This is clearly the case for picture-naming experiments because, thanks to the collection of psycholinguistic norms on both pictures and their names, a large number of factors that affect naming speed and/or accuracy have been found. In the present study, a Bayesian meta-analysis was performed to determine the extent to which the variables that have generally been considered by researchers as important to control for are indeed worth taking into account. The meta-analysis revealed that most of the variables that are considered in picture-naming studies have a strong or very strong influence on naming speed (image agreement, name agreement, image variability/imageability, age of acquisition, and conceptual familiarity), whereas two variables that are very often taken into account (visual complexity and length) yielded null effects. The results were inconclusive for lexical frequency. At a methodological level, Bayesian meta-analyses constitute a very useful tool for guiding researchers when selecting materials for experiments.