Unbiased post-error slowing in interference tasks: A confound and a simple solution

We typically slow down after committing an error, an effect termed post-error slowing (PES). Traditionally, PES has been calculated by subtracting post-correct from post-error RTs. Dutilh et al. (Journal of Mathematical Psychology, 56(3), 208-216, 2012), however, showed PES values calculated in this way are potentially biased. Therefore, they proposed to compute robust PES scores by subtracting pre-error RTs from post-error RTs. Based on data from a large-scale study using the flanker task, we show that both traditional and robust PES estimates can be biased. The source of the bias are differential imbalances in the percentage of congruent vs. incongruent post-correct, pre-error, and post-error trials. Specifically, we found that post-correct, pre-error, and post-error trials were more likely to be congruent than incongruent, with the size of the imbalance depending on the trial type as well as the length of the response-stimulus interval (RSI). In our study, for trials preceded by a 700-ms RSI, the percentages of congruent trials were 62% for post-correct trials, 66% for pre-error trials, and 56% for post-error trials. Relative to unbiased estimates, these imbalances inflated traditional PES estimates by 37% (9 ms) and robust PES estimates by 42% (16 ms) when individual-participant means were calculated. When individual-participant medians were calculated, the biases were even more pronounced (40% and 50% inflation, respectively). To obtain unbiased PES scores for interference tasks, we propose to compute unweighted individual-participant means by initially calculating mean RTs for congruent and incongruent trials separately, before averaging congruent and incongruent mean RTs to calculate means for post-correct, pre-error and post-error trials.

Implicit sequence learning: Inter-stimulus interval and subjective experience

In this research of implicit sequence learning we examined the difference between two groups, using constant inter-stimulus interval (ISI, 770 ms) and the standard, constant response-stimulus interval (RSI, 170 ms) in the Alternating Serial Reaction Time (ASRT) task (Howard & Howard, 1997). Moreover, we examined the subjective experience of participants during the task with three short questions about three factors: boredom, anxiety, and whether the participant concentrated on accuracy or rather on speed. In case of constant response-stimulus interval, the inter-stimulus interval were shorter, the responses were faster, but there was no difference in accuracy or learning. In the case of constant inter-stimulus interval, we found a correlation between learning and accuracy, while this correlation was not present in the case of constant response-stimulus interval. The participants got increasingly bored, their anxiety did not change, but they were concentrating more and more on speed – this latter tendency was significantly diminished in the case of constant inter-stimulus interval. In respect of these factors we did not find any other difference between the two groups. In the case of constant response-stimulus interval we found a significant negative correlation between boredom and learning, while this correlation was not found in the case of constant inter-stimulus interval. No other correlations were found between learning and subjective factors.

The interplay of crossmodal attentional preparation and modality compatibility in cued task switching

Two experiments examined the influence of preparation on modality compatibility effects in task switching. The term modality compatibility refers to the similarity between the stimulus modality and the modality of response-related sensory consequences. Previous research showed evidence for modality compatibility benefits in task switching when participants switched either between two modality compatible tasks (auditory-vocal and visual-manual) or between two modality incompatible tasks (auditory-manual and visual-vocal). In this study, we investigated the influence of active preparation on modality compatibility effects in task switching. To this end, in Experiment 1, we introduced unimodal modality cues, whereas in Experiment 2, bimodal abstract cues were used. In both experiments, the cue-stimulus interval (CSI) was manipulated while holding the response-stimulus interval (RSI) constant. In both experiments, we found not only decreased switch costs with long CSI but also the elimination of the residual switch costs. More importantly, this preparation effect did not modulate the modality compatibility effect in task switching. To account for this data pattern, we assume that cue-based preparation of switches by modality mappings was highly effective and produced no residual reaction time (RT) costs with long CSI.