Phasic alertness reverses the beneficial effects of accessory stimuli on choice reaction

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.

Phasic alerting in visual search tasks

Many tasks require one to search for and find important objects in the visual environment. Visual search is strongly supported by cues indicating target objects to mechanisms of selective attention, which enable one to prioritise targets and ignore distractor objects. Besides selective attention, a major influence on performance across cognitive tasks is phasic alertness, a temporary increase of arousal induced by warning stimuli (alerting cues). Alerting cues provide no specific information on whose basis selective attention could be deployed, but have nevertheless been found to speed up perception and simple actions. It is still unclear, however, how alerting affects visual search. Therefore, in the present study, participants performed a visual search task with and without preceding visual alerting cues. Participants had to report the orientation of a target among several distractors. The target saliency was low in Experiment 1 and high in Experiment 2. In both experiments, we found that visual search was faster when a visual alerting cue was presented before the target display. Performance benefits occurred irrespective of how many distractors had been presented along with the target. Taken together, the findings reveal that visual alerting supports visual search independently of the complexity of the search process and the demands for selective attention.

Vision rivals audition in alerting humans for fast action

Successful behaviour requires that humans act promptly upon the ubiquitous rapid changes in the environment. Prompt actions are supported by phasic alertness, the increased readiness for perception and action elicited by warning stimuli (alerting cues). Audition is assumed to induce phasic alertness for action faster and more strongly than other senses. Here, we show that vision can be equally effective as audition. We investigated the temporal evolution and the effectiveness of visual and auditory alerting for action in a speeded choice task, while controlling for basic sensitivity differences between the modalities that are unrelated to action control (by matching auditory and visual stimuli according to reaction times in a prior simple detection task). Results revealed that alerting sped up responses, but this happened equally fast and equally strong for visual and auditory alerting cues. Thus, these findings argue that vision rivals audition in phasic alerting for prompt actions, and suggest that the underlying mechanisms work across both modalities.

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.

Phasic alertness boosts representational momentum

The final location of a moving object is always misremembered in the direction of the object’s motion; this occurrence is called representational momentum. Three experiments were conducted to investigate the effects of phasic alertness on representational momentum by presenting a visual or auditory warning cue. In experiment 1, the mouse pointer paradigm was used, and the results showed that external warning cues increased forward displacement. Experiment 2 indicated that the effects of phasic alertness and speed of motion on representational momentum were independent. In experiment 3, the probe paradigm was used, and the results showed that external warning cues increased forward displacement as well as participants’ sensitivity to the difference between the target and probe positions. These findings prove that phasic alertness boosts rather than reduces representational momentum. We propose that phasic alertness might influence representational momentum by modulating the process of executive control in the retention interval.

Phasic Alertness is Unaffected by the Attentional Set for Orienting

Warning stimuli preceding target stimuli for behaviour improve behavioural performance, which is referred to as phasic alerting. Similar benefits occur due to preceding orienting cues that draw spatial attention to the targets. It has long been assumed that alerting and orienting effects arise from separate attention systems, but recent views call this into question. As it stands, it remains unclear if the two systems are interdependent, or if they function independently. Here, we investigated whether the current attentional set for orienting modulates the effectiveness of alerting. In three experiments, participants classified visual stimuli in a speeded fashion. These target stimuli were preceded by orienting cues that could predict the target's location, by alerting cues that were neutral regarding the target's location, or by no cues. Alerting cues and orienting cues consisted of the same visual stimuli, linking alerting cues with the attentional set for orienting. The attentional set for orienting was manipulated in blocks, in which orienting cues were either informative or uninformative about the target's location. Results showed that while alerting generally enhanced performance, alerting was unaffected by the informativeness of the orienting cues. These findings show that alerting does not depend on the attentional set that controls orienting based on the informational value of orienting cues. As such, the findings provide a simple dissociation of mechanisms underlying phasic alertness and spatial attentional orienting.

Temporal expectancy modulates stimulus-response integration

We can use information derived from passing time to anticipate an upcoming event. If time before an event varies, responses towards this event become faster with increasing waiting time. This variable-foreperiod effect has been often observed in response-speed studies. Different action control frameworks assume that response and stimulus features are integrated into an event file that is retrieved later if features repeat. Yet the role of foreperiods has so far not been investigated in action control. Thus, we investigated the influence of foreperiod on the integration of action-perception features. Participants worked through a standard distractor-response binding paradigm where two consecutive responses are made towards target letters while distractor letters are present. Responses and/or distractors can repeat or change from first to second display, leading to partial repetition costs when only some features repeat or repetition benefits when all features repeat (the difference constituting distractor-response binding). To investigate the effect of foreperiod, we also introduced an anti-geometric distribution of foreperiods to the time interval before the first response display. We observed that distractor-response binding increased with increasing foreperiod duration, and speculate that this was driven by an increase in motor readiness induced by temporal expectancy.

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.

Temporal preparation in adults with autistic spectrum disorder: The variable foreperiod effect

Research suggested the possibility that temporal cognition may be different in autistic spectrum disorder (ASD). Although there are some empirical studies examining timing ability in these individuals, to our knowledge, no one directly assessed the ability to predict when an event will occur. Here, we report a study on implicit temporal preparation in individuals with ASD as indexed by the variable foreperiod (FP) effect. We compared a group of adult ASD participants to a group of typically-developed (TD) controls, for their respective abilities to utilize implicit temporal information in a simple detection task with three different preparatory intervals (FP, short, middle and long). Participants were given a warning tone to signal an imminent stimulus, and asked to press a key as quickly as they could upon detection of the stimulus. Both groups were able to use implicit temporal information, as revealed by both the variable-FP effect (i.e., faster response for targets appearing after a long FP) and asymmetric sequential effects (i.e., slower response in short-FP trials following a previous long-FP trial). The TD group exhibited a faster response in a long-FP trial that was preceded by short-FP one, whereas the ASD group did not, as reflected in their higher percentage of response omissions for a target that appeared later than in the previous trial. The reduced ability of ASD participants to modulate their responses under these conditions might reflect a difficulty in time-based monitoring of stimulus occurrence. LAY SUMMARY: Time-processing may be different in autistic spectrum disorder (ASD). This study addressed the ability to anticipate a relevant stimulus's onset according to predictable interstimulus intervals comparing adults with ASD and typically developed controls. We found that ASD participants did not benefit from temporal preparation when stimulus appeared later than previously attended. This suggests a reduced ability in detecting implicit temporal regularities between events.