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It has been proposed that the Stroop effect has a composite nature as different processing levels contribute to it. Specifically, the multiple loci hypothesis distinguishes between stimulus-based, response-based and task conflicts (Parris et al., 2022). In the present study, our aim is to directly decompose the Stroop effect by separately measuring each of these sub-components. Moreover, considering that the Stroop effect is the sum of interference and facilitation, these sub-components should ideally comprise both an interfering and a facilitating part. However, previous studies mostly focused on interference or the overall Stroop effect only. Therefore, here, to separately assess interference and facilitation at the stimulus and response loci, we will also use neutral stimuli, which will be contrasted to incongruent and congruent ones. By contrast, the task locus necessarily entails only interference caused by the simultaneous presence of two tasks (i.e, the activation of a secondary task cannot facilitate the execution of the primary task). To pursue our aims, we will design different experimental tasks characterized by specific types of interference (and facilitation), except for the Stroop task, which comprises all interference and facilitation levels. For what concerns the first two interference and facilitation types, we will use the dimensional overlap model and the relative taxonomy proposed by Kornblum (1992) as a reference guide. Based on that, we will design i) a Flanker task to investigate the stimulus locus, thanks to the overlap between relevant and irrelevant stimulus features, ii) a Simon task to explore the response locus, thanks to the overlap between the irrelevant stimulus feature and the response. Moreover, we will design a Stimulus-Response Compatibility task (SRC) that, by having the overlap between the relevant stimulus and the response, will be used as a baseline task due to the absence of both interference and facilitation effects. Lastly, to isolate the effect of task conflict, we will use a task-switching paradigm, wherein subjects will be required to switch between the Simon and the SRC tasks. The assumption here is that embedding the SRC task within a mixed block in which the Simon task is also present, this latter task set (i.e., process and respond to the stimulus color) will also be activated when participants will perform the SRC task (i.e., process and respond to the stimulus position), even during repeat neutral SRC trials, in which no task switching is required and no irrelevant stimulus color is present, thus causing task-level interference.

It has been proposed that the Stroop effect has a composite nature as different processing levels contribute to it. Specifically, the multiple loci hypothesis distinguishes between stimulus-based, response-based and task conflicts (Parris et al., 2021). In a previous pre-registered study (see https://osf.io/zhckv), we aimed to directly decompose the Stroop effect by separately measuring each of these sub-components, while also distinguishing between interference and facilitation at the stimulus and response levels. In the present study, our aim is to make a further step in the same direction, by more directly addressing our previous experimental questions. a. As in our previous study, we will design different experimental tasks characterized by stimulus and response interference (and facilitation), except for the Stroop task, which comprises all interference and facilitation levels, and we will do this by using Kornblum’s (1992) taxonomy as reference guide. To explore the response locus, we will use the same paradigm of our previous study, namely the Simon task (Sim, irrelevant stimulus – response overlap), whereas we will use a Stroop-like task in place of the Flanker task to assess the stimulus locus. The Flanker task, indeed, presents some methodological characteristics, like entailing the same process (ie, color identification) in both the relevant and irrelevant tasks and thus requiring the use of physically separate stimuli to signal the task-relevant and -irrelevant stimulus dimensions, which entails the assumption that color identification has different levels of automaticity based on its task-relevance. By contrast, the Stroop-like task entails two distinct tasks, which, in this study, will be color identification and reading (we will call this task verbal Stroop, VS). Moreover, the Stroop-like task implies the overlap between relevant and irrelevant stimulus features, but since responses to verbal stimuli will be given manually, no stimulus-response overlap is present, distinguishing this task from the Stroop task. b. Compared to our previous study, here we will measure task interference more directly. Indeed, we previously used a task-switching paradigm with subjects required to switch between the Simon and the SRC tasks (see https://osf.io/zhckv for more details) and we analyzed neutral SRC trials, in which no task switching was required and no irrelevant stimulus color was present, to isolate task-level interference, assuming that they were affected by the concurrent activation of the other task set. However, by isolating task interference in this way, we used a task that differed greatly from the Stroop task (that we want to decompose) and required the use of the task-switching paradigm (for which we collected many trials, but we used less than half). Here we still use the same assumption, but we will directly manipulate the task interference by comparing paradigms involving a single task to paradigms involving the same task along with another conflicting task that is exogenously activated. We assume that task interference can be isolated by comparing neutral trials (thus free from other types of facilitation/interference) in paradigms involving two conflicting tasks to trials involving the same primary task and stimuli (which are necessarily neutral), but within single task paradigms. Indeed, the former neutral trials imply the same task as the second ones, but since they appear intermixed with congruent/incongruent trials, which activate also the alternative conflicting task, they also elicit the conflicting task and are thus affected by task interference, yielding a worse performance than single task neutral trials (free from all types of facilitation and interference). In practical terms, for each paradigm involving task conflict for the presence of two tasks, we will include in the study a paradigm implying just each of the two tasks so to have one single task block for each task, which will be the following: Position task (POS, corresponding to the SRC task used in the previous study), Direction task (DIR), Word task (WRD), and Color task (COL). These single tasks are needed as the task interference paradigms are the Simon task (Sim, COL vs POS), two verbal Stroop-like tasks, requiring participants to indicate either the stimulus ink color, like in the original color-word Stroop (VSc, COL vs WRD), or the color indicated by the word (VSw, WRD vs COL), respectively, and two spatial Stroop tasks, requiring participants to indicate either the stimulus direction, like in our original spatial Stroop task (SSd, DIR vs POS), or its position (SSp POS vs DIR), respectively. c. A further novelty of the present study is a greater attention and a better focus given to task automaticity, as we predict it has a significant role in modulating the performance in the paradigms involving task conflict. Specifically, we define automaticity as the strength/easiness of processing of a stimulus feature. Automaticity was already considered in our previous study, but we just focused on the automaticity of the relevant task (i.e., the automaticity of processing the relevant stimulus features). In contrast, here, by separately measuring the performance in each single task, we will be able to estimate the precise weight of automaticity of each task, regardless of whether it is relevant or irrelevant. Moreover, as in the previous study, we assumed that automaticity also reflects how prepotent are the responses elicited by the tasks (or how automatic is the S-R mapping). d. We will also make a step further in estimating task asymmetry, that is, the difference in the automaticity of the two tasks involved in conflict tasks. In our previous study, we (arbitrarily) assigned an asymmetry score to each conflict paradigm, whereas here, by obtaining the precise estimates of automaticity for each task, we will be able to directly compute it by calculating the ratio between the automaticity of the two tasks (i.e., automaticity irrelevant task/automaticity relevant task). We indeed expect that task interference would be greater when the irrelevant task is more automatic than the relevant one. Therefore, task interference effects will be weighted using the corresponding task asymmetry estimates. e. Similarly, we will also take into account the automaticity of the irrelevant task to refine our hypotheses about the facilitation, interference, and congruency effects at both the stimulus and response levels. In particular, here we assume that the degree of stimulus/response facilitation/interference exerted by the irrelevant task directly depend on its automaticity: if the processing of the irrelevant information and its S-R mapping are more automatic, we assume that they should exert a greater facilitation/interference in processing and responding to the relevant information, with greater facilitation/interference at both the stimulus and response levels. f. Finally, based on the results of our previous study, to further refine our hypotheses about the facilitation, interference, and congruency effects, we will consider the relative weight of task interference and both stimulus and response loci of facilitation/interference.

Italy was the first Western country with numerous COVID-19 infections that underwent a strong lockdown. This represents the first threat-related mass isolation in the history that can be in-depth studied by scientists to understand the side effects of pandemic lockdown in the psychophysical domain. There is increasing evidence that Italian lockdown was associated with larger incidence of stress, anxiety, and mood symptoms. It was thus expected that, at a more basic level, also emotion perception -namely how an individual judges the affective content of common words- changed substantially during lockdown, especially in individuals with high COVID-19 fear and high negative affect. We measured the effects of this long-term isolation and the related pandemic phobia in an online survey on 71 healthy Italian participants. They completed the Positive and Negative Affect Schedule and Fear of COVID-19 Scale and judged valence, arousal, and dominance of words either related or unrelated to COVID-19, as identified by Google search trends. We found that lockdown imposed by the COVID-19 epidemic had a substantial impact on participants’ emotional responses. Moreover, emotional judgments changes from normative data varied depending on word type and individuals’ emotional state, revealing early signals of individuals’ mental distress to COVID-19 confinement. Lower valence and dominance judgments were given only to COVID-19-related words by individuals with less negative feelings and COVID-19 fear, but also to COVID-19-unrelated words by individuals with more negative feelings and COVID-19 fear. Moreover, arousal judgments for all words decreased and increased, respectively, for individuals with less and more negative feelings and COVID-19 fear. With respect to more direct but demanding and expensive tools such as surveys and questionnaires, the methods used here allow to measure more conveniently but reliably the emotional alteration and clinical psychiatric risk of population through the analysis of word use in the web and their affective connotation.

The spatial Stroop task measures the ability to resolve interference between relevant and irrelevant spatial information. Besides satisfying the requirements for being a proper Stroop task, its purely spatial version ensures methodological advantages over the original color-word verbal task. We recently proposed a 4-choice spatial Stroop task that benefits from such advantages, which requires participants to indicate the direction of an arrow while ignoring its position in one of the screen corners. However, its peripheral spatial arrangement might represent a methodological weakness and could introduce experimental confounds. Thus, with the aim of improving our “Peripheral” spatial Stroop, we designed and made available five novel spatial Stroop tasks (Perifoveal, Navon, Figure-Ground, Flanker, and Saliency), wherein the experimental stimuli appeared at the center of the screen. In a within-subjects online study, we compared the six versions to identify which task produced the largest but also the most reliable and robust Stroop effect. Indeed, although internal reliability is frequently overlooked, its estimate is fundamental, also in light of the recently proposed reliability paradox. Data analyses were performed using both the classical general linear model analytical approach and two multilevel modelling approaches (linear mixed models and random coefficient analysis), which specifically served for more accurately estimating the Stroop effect by explaining intra-subject, trial-by-trial variability. We then assessed our results based on their robustness to such analytic flexibility. Overall, our results indicate that the Perifoveal spatial Stroop is the best alternative task for its statistical properties and methodological advantages. Interestingly, our results also indicate that the Peripheral and Perifoveal Stroop effects were not only the largest, but also the one with highest and most robust internal reliability.