Alertness and cognitive control: Interactions in the spatial Stroop task

Alerting effects require the absence of surprise

Ongoing actions are interrupted for a brief period of time whenever salient and expectancy-discrepant stimuli (surprise stimuli) interfere with the present task set. By contrast, salient stimuli (alerting cues) preceding targets can facilitate behaviour by reducing time to initiate actions. Both phenomena seem to be at odds with each other as actions are either impaired or facilitated. Therefore, in the present study, we asked how surprise and alerting effects interact. In two experiments, participants performed choice reaction tasks without any prior knowledge of the impending alerting cue. After a baseline period of trials without an alerting cue, the alerting cue was presented for the first time. It was found that the initial presentation of the alerting cue significantly slowed down reaction times. However, after just a single trial this impairment went away. This reveals that the beneficial effects of alerting for action presuppose that alerting cues are expected and represented in the top-down task set. As such, the present findings challenge the standard view of phasic alerting as a bottom-up and entirely stimulus-driven phenomenon.

Effects of alerting signals on the spatial Stroop effect: evidence for modality differences

Reaction times and error rates to a target's identity are impaired when the target is presented in a location that mismatches the response required, relative to situations where the location of the target and required response overlap (the Simon effect) and the same is true when the target's identity conveys spatial information (the spatial Stroop effect). Prior studies have found that visual versions of the spatial Stroop effect are magnified when alerting cues appear before the target and results are consistent with a dual-route framework where alerting cues boost automatic stimulus-response motor associations through the direct processing route. However, the influence of alerting signals on auditory versions of the spatial Stroop effect have not been tested and there are reasons to believe that the alerting-congruency interaction may differ across stimulus modality. In two experiments the effects of alerting cues on auditory (Experiment 1; N = 98) and visual (Experiment 2; N = 97) spatial Stroop effects are examined. Results show that alerting cues boost the spatial Stroop effect with visual stimuli but not auditory stimuli and a distributional analysis provides support for there being modality differences in the decay (or inhibition) of response-code activation. Implications for explanations of the alerting-congruence interaction are discussed.

Testing the saliency-based account of phasic alertness

As an essential component of the human attention system, the effect of phasic alertness refers to the change of performance with the presence of a preceding warning signal. Weinbach and Henik (Cognition, 133 (2), 414-419, 2014) argued that phasic alertness is an adaptive mechanism that diverts attention to salient events. This mechanism enhances selective attention when the critical event is more salient than others. When selective attention to less salient details is required, phasic alertness can lead to more interference from task-irrelevant information. The experiment on which this saliency-based account of phasic alertness is based has not been replicated. In two experiments, the present study attempted to replicate the alertness-related findings of Weinbach and Henik. Although we used a similar design, the results did not reveal evidence for an interaction between phasic alertness and response congruency in the global/local processing task. Our results do not support the saliency-based account of phasic alertness. We argue that more systematic investigation is needed for this phasic alertness account.

The Stroop legacy: A cautionary tale on methodological issues and a proposed spatial solution

The Stroop task is a seminal paradigm in experimental psychology, so much that various variants of the classical color-word version have been proposed. Here we offer a methodological review of them to emphasize the importance of designing methodologically rigorous Stroop tasks. This is not an end by itself, but it is fundamental to achieve adequate measurement validity, which is currently hindered by methodological heterogeneity and limitations. Among the several Stroop task variants in the literature, our methodological overview shows that the spatial Stroop task is not only a potentially methodologically adequate variant, which can thus assure measuring the Stroop effect with the required validity, but it might even allow researchers to overcome some of the methodological limitations of the classical paradigm due to its use of verbal stimuli. We thus focused on the spatial Stroop tasks in the literature to verify whether they really exploit such inherent potentiality. However, we show that this was generally not the case because only a few of them (1) are purely spatial, (2) ensure both all the three types of conflicts/facilitations (at the stimulus, response, and task levels) and the dimensional overlaps considered fundamental for yielding a complete Stroop effect according to the multiple loci account and Kornblum's theory, respectively, and (3) controlled for low-level binding and priming effects that could bias the estimated Stroop effect. Based on these methodological considerations, we present some examples of spatial Stroop tasks that, in our view, satisfy such requirements and, thus, ensure producing complete Stroop effects.

Warning signals only support the first action in a sequence

Acting upon target stimuli from the environment becomes faster when the targets are preceded by a warning (alerting) cue. Accordingly, alerting is often used to support action in safety-critical contexts (e.g., honking to alert others of a traffic situation). Crucially, however, the benefits of alerting for action have been established using laboratory tasks assessing only simple choice reactions. Real-world actions are considerably more complex and mainly consist of sensorimotor sequences of several sub-actions. Therefore, it is still unknown if the benefits of alerting for action transfer from simple choice reactions to such sensorimotor sequences. Here, we investigated how alerting affected performance in a sequential action task derived from the Trail-Making-Test, a well-established neuropsychological test of cognitive action control (Experiment 1). In addition to this task, participants performed a classic alerting paradigm including a simple choice reaction task (Experiment 2). Results showed that alerting sped up responding in both tasks, but in the sequential action task, this benefit was restricted to the first action of a sequence. This was the case, even when multiple actions were performed within a short time (Experiment 3), ruling out that the restriction of alerting to the first action was due to its short-lived nature. Taken together, these findings reveal the existence of an interface between phasic alertness and action control that supports the next action.

Effects of a neutral warning signal under increased temporal uncertainty

Han and Proctor (2022a, Quarterly Journal of Experimental Psychology, 75[4], 754-764) reported that in a visual two-choice task, compared with a no-warning condition, a neutral warning tone caused shorter reaction times (RTs) but at the expense of an increase in error percentages (a speed-accuracy trade-off) at a constant 50-ms foreperiod but shorter RTs without an increase in error percentages at a 200-ms foreperiod. Also, the spatial compatibility of stimulus-response mappings was found to interact with the foreperiod effect on RT. We conducted three experiments to investigate whether these findings can be replicated without the constancy of foreperiod within a trial block. In Experiments 1 and 2, participants performed the same two-choice task as in Han and Proctor's study but with the foreperiod randomly varied among 50, 100, and 200 ms and RT feedback provided after each response. Results showed that as the foreperiod increased, RT decreased while EP increased, demonstrating a consistent speed-accuracy trade-off. Also, the mapping effect was found to be largest at the 100-ms foreperiod. In Experiment 3, RT feedback was not provided, and the warning tone speeded responses without evidence of an increase in error percentage. We conclude that the enhanced information processing at a 200-ms foreperiod depends on constancy of foreperiod within a trial block, whereas the mapping-foreperiod interaction found in Han and Proctor is relatively unaffected by increased temporal uncertainty.

Replacing vertical actions by mouse movements: a web-suited paradigm for investigating vertical spatial associations

The number of web-based studies in experimental psychology has been growing tremendously throughout the last few years. However, a straightforward web-based implementation does not exist for all types of experimental paradigms. In the current paper, we focus on how vertical response movements-which play a crucial role in spatial cognition and language research-can be translated into a web-based setup. Specifically, we introduce a web-suited counterpart of the vertical Stroop task (e.g., Fox & Shor, in Bull Psychon Soc 7:187-189, 1976; Lachmair et al., in Psychon Bull Rev 18:1180-1188, 2011; Thornton et al., in J Exp Psychol Hum Percept Perform 39:964-973, 2013). We employed nouns referring to entities typically located in lower or upper vertical space (e.g., "worm" and "bird", respectively) in Experiments 1 and 2, and emotional valence words associated with a crouched or an upward bodily posture (e.g., "sadness" and "excitement", respectively) in Experiment 3. Depending on the font color, our participants used their mouse to drag the words to the lower or upper screen location. Across all experiments, we consistently observed congruency effects analogous to those obtained with the lab paradigm using actual vertical arm movements. Consequently, we conclude that our web-suited paradigm establishes a reliable approach to examining vertical spatial associations.

Urgency forces stimulus-driven action by overcoming cognitive control

Intelligent behavior requires to act directed by goals despite competing action tendencies triggered by stimuli in the environment. For eye movements, it has recently been discovered that this ability is briefly reduced in urgent situations (Salinas et al., 2019). In a time-window before an urgent response, participants could not help but look at a suddenly appearing visual stimulus, even though their goal was to look away from it. Urgency seemed to provoke a new visual-oculomotor phenomenon: A period in which saccadic eye movements are dominated by external stimuli, and uncontrollable by current goals. This period was assumed to arise from brain mechanisms controlling eye movements and spatial attention, such as those of the frontal eye field. Here, we show that the phenomenon is more general than previously thought. We found that also in well-investigated manual tasks, urgency made goal-conflicting stimulus features dominate behavioral responses. This dominance of behavior followed established trial-to-trial signatures of cognitive control mechanisms that replicate across a variety of tasks. Thus together, these findings reveal that urgency temporarily forces stimulus-driven action by overcoming cognitive control in general, not only at brain mechanisms controlling eye movements.

Comparing saccadic and manual responses in the attention network test

Attention is proposed to be a system of multiple functional networks, including alertness, orienting and executive control. A popular experimental paradigm for testing these networks and their interactions within a single design is the Attentional Networks Test (ANT) (Fan et al., 2002). The role of the oculomotor system in these various networks, however, has not been tested despite the strong link between attention and eye movements. We modified the executive control component of the manual response ANT version (ANTm) that allows testing the networks' involvement with oculomotor responses. Specifically, we used a central target to signal pro or anti-saccades that allows us to match the saccadic response compatibility of the original ANTm. We conducted three experiments to compare interactions of the networks between the traditional ANTm that used a flanker task response, our new ANTs with saccadic responses signalled with a fixation arrow, and a manual response version with the response arrow at fixation (ANTf). Results for all three experiments showed typical main effects of all three attention networks, but we observed differences in their interactions. The ANTm showed only an interaction of alerting enhancing the orienting; ANTs showed a congruency by orienting interaction with the orienting effect only observed for pro-saccades. The ANTf showed both alerting by orienting, and orienting by congruency. Although the saccadic response did differ from the original ANTm, key differences were also highlighted by the switch from peripheral to central target. Overall the proposed ANTf is a valid tool to test main effects of attentional networks. Further investigation of interaction differences between manual and oculomotor systems is required.

Effects of a neutral warning signal on spatial two-choice reactions

Posner et al. reported that, at short fixed foreperiods, a neutral warning tone reduced reaction times (RTs) in a visual two-choice task while increasing error rates for both spatially compatible and incompatible stimulus-response mappings. Consequently, they concluded that alertness induced by the warning does not affect the efficiency of information processing but the setting of a response criterion. We conducted two experiments to determine the conditions under which the trade-off occurs. In Experiment 1, participants performed the same two-choice task as in Posner et al.'s study without RT feedback. Results showed that the warning tone speeded responses with no evidence of speed/accuracy trade-off. In Experiment 2, RT feedback was provided after each response, and a speed/accuracy trade-off was found for the 50-ms foreperiod. However, better information-processing efficiency was evident for the 200-ms foreperiod. We conclude that the foreperiod effect of a 50-ms foreperiod is a result of response criterion adjustment and that providing trial-level RT feedback is critical for replicating this pattern. However, fixed foreperiods of 200 ms or longer benefit both speed and accuracy, implying a more controlled preparation component that improves response efficiency.

Potential and efficiency of statistical learning closely intertwined with individuals' executive functions: a mathematical modeling study

Statistical learning (SL) is essential in enabling humans to extract probabilistic regularities from the world. The ability to accomplish ultimate learning performance with training (i.e., the potential of learning) has been known to be dissociated with performance improvement per amount of learning time (i.e., the efficiency of learning). Here, we quantified the potential and efficiency of SL separately through mathematical modeling and scrutinized how they were affected by various executive functions. Our results showed that a high potential of SL was associated with poor inhibition and good visuo-spatial working memory, whereas high efficiency of SL was closely related to good inhibition and good set-shifting. We unveiled the distinct characteristics of SL in relation to potential and efficiency and their interaction with executive functions.

Virtual training leads to physical, cognitive and neural benefits in healthy adults

Physical activity, such as high-intensity intermittent aerobic exercise (HIE), can improve executive functions. Although performing strength or aerobic training might be problematic or not feasible for someone. An experimental situation where there is no actual movement, but the body shows physiological reactions, is during the illusion through immersive virtual reality (IVR). We aimed to demonstrate whether a virtual HIE-based intervention (vHIE) performed exclusively by the own virtual body has physical, cognitive, and neural benefits on the real body. 45 healthy young adults (cross-over design) experienced HIE training in IVR (i.e., the virtual body performed eight sets of 30 s of running followed by 30 s of slow walking, while the subject is completely still) in two random-ordered conditions (administered in two sessions one week apart): the virtual body is displayed in first-person perspective (1PP) or third-person perspective (3PP). During the vHIE, we recorded the heart rate and subjective questionnaires to confirm the effectiveness of the illusion; before and after vHIE, we measured cortical hemodynamic changes in the participants' left dorsolateral prefrontal cortex (lDLPFC) using the fNIRS device during the Stroop task to test our main hypothesis. Preliminary, we confirmed that the illusion was effective: during the vHIE in 1PP, subjects' heart rate increased coherently with the virtual movements, and they reported subjective feelings of ownership and agency. Primarily, subjects were faster in executing the Stroop task after the vHIE in 1PP; also, the lDLPFC activity increased coherently. Clinically, these results might be exploited to train cognition and body simultaneously. Theoretically, we proved that the sense of body ownership and agency can affect other parameters, even in the absence of actual movements.