Exogenous Attentional Capture Research Articles

Hello from the other side: Robust contralateral interference in tactile detection

Touch is unique among the sensory modalities in that our tactile receptors are spread across the body surface and continuously receive different inputs at the same time. These inputs vary in type, properties, relevance according to current goals, and, of course, location on the body. Sometimes, they must be integrated, and other times set apart and distinguished. Here, we investigate how simultaneous stimulation to different body sites affects tactile cognition. Specifically, we characterized the impact of irrelevant tactile sensations on tactile change detection. To this end, we embedded detection targets amidst ongoing performance, akin to the conditions encountered in everyday life, where we are constantly confronted with new events within ongoing stimuli. In the set of experiments presented here, participants detected a brief intensity change (.04 s) within an ongoing vibrotactile stimulus (1.6 s) that was always presented in a constantly attended location. The intensity change (i.e., the detection target) varied parametrically, from hardly detectable to easily detectable. In half of the trials, irrelevant ongoing stimulation was simultaneously presented to a site across the body midline, but participants were instructed to ignore it. In line with previous bimanual studies employing brief onset targets, we document robust interference on performance due to the irrelevant stimulation at each of the measured body sites (homologous and nonhomologous fingers, and the contralateral ankle). After describing this basic phenomenon, we further examine the conditions under which such interference occurs in three additional tasks. In each task, we honed in on a different aspect of the stimulation protocol (e.g., hand distance, the strength of the irrelevant stimulation, the detection target itself) in order to better understand the principles governing the observed interference effects. Our findings suggest a minimal role for exogenous attentional capture in producing the observed interference effects (Exp. 2), and a principled distribution of attentional resources or sensory integration between body sides (Exps. 3, 4). In our last study (Exp. 4), we presented bilateral tactile targets of varying intensities to both the relevant and irrelevant stimulation sites. We then characterized the degree to which the irrelevant stimulation is also processed. Our results—that participants’ perception of target intensity is always proportional to the combined bilateral signal—suggest that both body sites are equally weighed and processed despite clear instructions to attend only the target site. In light of this observation and participants’ inability to use selection processes to guide their perception, we propose that bilateral tactile inputs are automatically combined, quite possibly early in the hierarchy of somatosensory processing.

Tracking exogenous attentional capture in an urgent covert perceptual choice task

Tracking exogenous attentional capture in an urgent covert perceptual choice task

Exogenous Attention to Emotional Stimuli Presenting Realistic (3D) Looming Motion

Previous research shows that dynamic stimuli, on the one hand, and emotional stimuli, on the other, capture exogenous attention due to their biological relevance. Through neural (ERPs) and behavioral measures (reaction times and errors), the present study explored the combined effect of looming motion and emotional content on attentional capture. To this end, 3D-recreated static and dynamic animals assessed as emotional (positive or negative) or neutral were presented as distractors while 71 volunteers performed a line orientation task. We observed a two-phase effect: firstly (before 300 ms), early components of ERPs (P1p and N2po) showed enhanced exogenous attentional capture by looming positive distractors and static threatening animals. Thereafter, dynamic and static threatening distractors received enhanced endogenous attention as revealed by both late ERP activity (LPC) and behavioral (errors) responses. These effects are likely explained by both the emotional valence and the distance of the stimulus at each moment.

Attentional repulsion effects produced by feature-guided shifts of attention.

Attention shifts to particular objects in the visual field can distort perceptual location judgments. Visual stimuli are perceived to be shifted away from the current focus of attention (the attentional repulsion effect [ARE]). Although links between repulsion effects and stimulus-driven exogenous attentional capture have been demonstrated conclusively, it remains disputed whether AREs can also be elicited as a result of feature-guided attention shifts that are controlled by endogenous task sets. Here we demonstrate that this is indeed the case. Color singleton cues that appeared together with equiluminant gray items triggered repulsion effects only if they matched a current task-relevant color but not when their color was irrelevant. When target-color and nontarget-color singleton cues appeared in the same display, AREs emerged relative to the position of the target-color cue. By obtaining independent behavioral measures of perceptual repulsion and electrophysiological measures of attentional capture by target-color cues, we also showed that these two phenomena are correlated. Individuals who were more susceptible to attentional capture also produced larger AREs. These results confirm the existence of links between task-set contingent attentional capture and AREs. They also provide the first direct demonstration of the attentional nature of these effects with online brain activity measures: perceptual repulsion arises as the result of prior feature-guided attention shifts to specific locations in the visual field.

Does spatial attention modulate sensory memory?

According to some theoretical models, information contained in visual short-term memory (VSTM) consists of two main memory stages/storages: sensory memory, a system wherein information is stored for a brief time with high detail and low resistance to visual interference, and visual working memory, a low-capacity system wherein information is protected from visual interference and maintained for longer delays. Previous studies have consistently shown a strong relationship between attention and visual working memory. However, evidence is contradictory on whether or not attention modulates the construction and maintenance of visual representations in sensory memory. Here, we examined whether and how spatial attention differentially affects sensory and working memory contents, by separately analysing attentional costs and attentional benefits. Results showed that both sensory memory and visual working memory were reliably affected by the distribution of spatial attention, suggesting that spatial attention modulates the VSTM content starting from very early stages of memory storage. Moreover, endogenously attending a specific location led to similar performance in sensory and working memory, and therefore to larger attentional benefits in working memory (where there was more room for improvement than in sensory memory, because of worse performance in unattended locations). On the other hand, exogenous attentional capture by peripheral unpredictive cues produced invariant attentional costs and invariant attentional benefits regardless of the memory type, with performance being higher in sensory memory than in working memory even at the attended location.

Does noise sensitivity or attentional capacity predict cardiovascular responses to distracting sound?

Workplace noise may cause stress that has long-term implications for health. Employees in open-plan offices typically identify intermittently occurring background sounds as significant sources of stress, possibly because they distract attention away from intended tasks. Thus, individual differences in attention and noise sensitivity may explain individual differences in physiological responses to workplace noise. In previous research [Oliver, et al., in 176th Meeting of the Acoustical Society of America (2018)], we reported results from a preliminary analysis of 19 participants’ affective and electrodermal responses to working in background noise that included intermittent environmental sounds. Electrodermal responses were used as a measure of distraction because they constitute a primary component of the physiological orienting response, a multi-component response reflecting exogenous capture of attention. Our results suggested that individuals who are more sensitive to noise experienced greater frustration with the primary task, but there was no relationship between frustration and distraction as indexed by electrodermal responses. Here, we present additional analyses of an expanded dataset, focusing on attentional and cardiovascular measures (heart rate and pulse volume amplitude) previously linked to cognitive demand and noise annoyance (Francis et al., 2016) and relate these results to an overall characterization of the auditory orienting response.

Feature-Based Attention Samples Stimuli Rhythmically

Attention supports the allocation of resources to relevant locations and objects in a scene. Under most conditions, several stimuli compete for neural representation. Attention biases neural representation toward the response associated with the attended object [1, 2]. Therefore, an attended stimulusenjoys a neural response that resembles the response to that stimulus in isolation. Factors that determine and generate attentional bias have been researched, ranging from endogenously controlled processes to exogenous capture of attention [1-4]. Recent studies investigate the temporal structure governing attention. When participants monitor a single location, visual-target detection depends on the phase of an ∼8-Hz brain rhythm [5, 6]. When two locations are monitored, performance fluctuates at 4Hz for each location [7, 8]. The hypothesis is that 4-Hz sampling for two locations may reflect a common sampler that operates at 8Hz globally, which is divided between relevant locations [5-7,9]. The present study targets two properties of this phenomenon, called rhythmic-attentional sampling: first, sampling is typically described for selection over different locations. We examined whether rhythmic sampling is limited to selection over space or whether it extends to feature-based attention. Second, we examined whether sampling at 4Hz results from the division of an 8-Hz rhythm over two objects. We found that two overlapping objects defined by features are sampled at ∼4Hz per object. In addition, performance on a single object fluctuated at 8Hz. Rhythmic sampling of features did not result from temporal structure in eye movements.

Infants' visual sustained attention is higher during joint play than solo play: is this due to increased endogenous attention control or exogenous stimulus capture?

Previous research has suggested that when a social partner, such as a parent, pays attention to an object, this increases the attention that infants pay to that object during spontaneous, naturalistic play. There are two contrasting reasons why this might be: first, social context may influence increases in infants' endogenous (voluntary) attention control; second, social settings may offer increased opportunities for exogenous attentional capture. To differentiate these possibilities, we compared 12-month-old infants' naturalistic attention patterns in two settings: Solo Play and Joint Play with a social partner (the parent). Consistent with previous research, we found that infants' look durations toward play objects were longer during Joint Play, and that moments of inattentiveness were fewer, and shorter. Follow-up analyses, conducted to differentiate the two above-proposed hypotheses, were more consistent with the latter hypothesis. We found that infants' rate of change of attentiveness was faster during Joint Play than Solo Play, suggesting that internal attention factors, such as attentional inertia, may influence looking behaviour less during Joint Play.We also found that adults' attention forwards-predicted infants' subsequent attention more than vice versa, suggesting that adults' behaviour may drive infants' behaviour.Finally, we found that mutual gaze did not directly facilitate infant attentiveness. Overall, our results suggest that infants spend more time attending to objects during Joint Play than Solo Play, but that these differences are more likely attributable to increased exogenous attentional scaffolding from the parent during social play, rather than to increased endogenous attention control from the infant.

Orienting of attention with and without cue awareness

Many cognitive processes operate without consciousness, and exogenous attentional capture seems to be one of them. While endogenously attending to the opposite location of a cue cannot occur without cue awareness, attending the cued location in an exogenous or stimulus driven form can occur even when participants are not aware of the presence of the cue (McCormick, 1997). Orienting attention to a specific location shortens reaction times to supra-threshold stimuli, and increases the likelihood of consciously perceiving near-threshold stimuli in that location. Effects of unconscious cues have mostly been demonstrated in reaction times to supra-threshold targets. In some studies, unconscious cues were perceptually less salient than conscious cues, which introduced a confound between cue awareness and cue saliency. In the present study, we used near-threshold cues and targets, which were titrated to be consciously perceived in ~50% of the trials, therefore eliminating the cue saliency confound. Moreover, we explored for the first time the effects of cue awareness on the conscious perception of subsequently presented near-threshold targets. Our results demonstrate that when cues and targets did not spatially overlap, conscious cues enhanced target localization when they appeared near the target location. In contrast, non-consciously perceived cues impaired target localization when they appeared near the target location, producing a cost in detecting subsequently presented near-threshold targets. This indicates that attentional orienting by unconscious cues cannot be accounted for by the idea that attention modulates perceptual representations, boosting them nearer to the conscious threshold. Rather, the effect of unconscious cues on target localization is qualitatively different to that elicited by conscious cues.

Distracted by danger: Temporal and spatial dynamics of visual selection in the presence of threat.

Threatening stimuli are known to influence attentional and visual processes in order to prioritize selection. For example, previous research showed faster detection of threatening relative to nonthreatening stimuli. This has led to the proposal that threatening stimuli are prioritized automatically via a rapid subcortical route. However, in most studies, the threatening stimulus is always to some extent task relevant. Therefore, it is still unclear if threatening stimuli are automatically prioritized by the visual system. We used the additional singleton paradigm with task-irrelevant fear-conditioned distractors (CS+ and CS-) and indexed the time course of eye movement behavior. The results demonstrate automatic prioritization of threat. First, mean latency of saccades directed to the neutral target was increased in the presence of a threatening (CS+) relative to a nonthreatening distractor (CS-), indicating exogenous attentional capture and delayed disengagement of covert attention. Second, more error saccades were directed to the threatening than to the nonthreatening distractor, indicating a modulation of automatically driven saccades. Nevertheless, cumulative distributions of the saccade latencies showed no modulation of threat for the fastest goal-driven saccades, and threat did not affect the latency of the error saccades to the distractors. Together these results suggest that threatening stimuli are automatically prioritized in attentional and visual selection but not via faster processing. Rather, we suggest that prioritization results from an enhanced representation of the threatening stimulus in the oculomotor system, which drives attentional and visual selection. The current findings are interpreted in terms of a neurobiological model of saccade programming.

S-ketamine influences strategic allocation of attention but not exogenous capture of attention.

We investigated whether s-ketamine differentially affects strategic allocation of attention. In Experiment 1, (1) a less visible cue was weakly masked by the onsets of competing placeholders or (2) a better visible cue was not masked because it was presented in isolation. Both types of cue appeared more often opposite of the target (75%) than at target position (25%). With this setup, we tested for strategic attention shifts to the opposite side of the cues and for exogenous attentional capture toward the cue's side in a short cue-target interval, as well as for (reverse) cueing effects in a long cue-target interval after s-ketamine and after placebo treatment in a double-blind within-participant design. We found reduced strategic attention shifts after cues presented without placeholders for the s-ketamine compared to the placebo treatment in the short interval, indicating an early effect on the strategic allocation of attention. No differences between the two treatments were found for exogenous attentional capture by less visible cues, suggesting that s-ketamine does not affect exogenous attentional capture in the presence of competing distractors. Experiment 2 confirmed that the competing onsets of the placeholders prevented the strategic cueing effect. Taken together, the results indicate that s-ketamine affects strategic attentional capture, but not exogenous attentional capture. The findings point to a more prominent role of s-ketamine during top-down controlled forms of attention that require suppression of automatic capture than during automatic capture itself.

The role of sustained attention in shift-contingent change blindness

Previous studies of change blindness have examined the effect of temporal factors (e.g., blank duration) on attention in change detection. This study examined the effect of spatial factors (i.e., whether the locations of original and changed objects are the same or different) on attention in change detection, using a shift-contingent change blindness task. We used a flicker paradigm in which the location of a to-be-judged target image was manipulated (shift, no-shift). In shift conditions, the image of an array of objects was spatially shifted so that all objects appeared in new locations; in no-shift conditions, all object images of an array appeared at the same location. The presence of visual stimuli (dots) in the blank display between the two images was.manipulated (dot, no-dot) under the assumption that abrupt onsets of these stimuli would capture attention. Results indicated that change detection performance was improved by exogenous attentional capture in the shift condition. Thus, we suggest that attention can play an important role in change detection during shift-contingent change blindness.

The effects of stimulus-driven competition and task set on involuntary attention.

It is well established that involuntary attention—the exogenous capture of attention by salient but task-irrelevant stimuli—can strongly modulate target detection and discrimination performance. There is an ongoing debate, however, about how involuntary attention affects target performance. Some studies suggest that it results from enhanced perception of the target, whereas others indicate instead that it affects decisional stages of information processing. From a review of these studies, we hypothesized that the presence of distractors and task sets are key factors in determining the effect of involuntary attention on target perception. Consistent with this hypothesis, here we found that noninformative cues summoning involuntary attention affected perceptual identification of a target when distractors were present. This cuing effect could not be attributed to reduced target location uncertainty or decision bias. The only condition under which involuntary attention improved target perception in the absence of distractors occurred when observers did not adopt a task set to focus attention on the target location. We conclude that the perceptual effects of involuntary attention depend on distractor interference and the adoption of a task set to resolve such stimulus competition.

Individual Differences in Infant Oculomotor Behavior During the Viewing of Complex Naturalistic Scenes.

Little research hitherto has examined how individual differences in attention, as assessed using standard experimental paradigms, relate to individual differences in how attention is spontaneously allocated in more naturalistic contexts. Here, we analyzed the time intervals between refoveating eye movements (fixation durations) while typically developing 11-month-old infants viewed a 90-min battery ranging from complex dynamic to noncomplex static materials. The same infants also completed experimental assessments of cognitive control, psychomotor reaction times (RT), processing speed (indexed via peak look during habituation), and arousal (indexed via tonic pupil size). High test–retest reliability was found for fixation duration, across testing sessions and across types of viewing material. Increased cognitive control and increased arousal were associated with reduced variability in fixation duration. For fixations to dynamic stimuli, in which a large proportion of saccades may be exogenously cued, we found that psychomotor RT measures were most predictive of mean fixation duration; for fixations to static stimuli, in contrast, in which there is less exogenous attentional capture, we found that psychomotor RT did not predict performance, but that measures of cognitive control and arousal did. The implications of these findings for understanding the development of attentional control in naturalistic settings are discussed.

The interaction of feature and space based orienting within the attention set

The processing of sensory information relies on interacting mechanisms of sustained attention and attentional capture, both of which operate in space and on object features. While evidence indicates that exogenous attentional capture, a mechanism previously understood to be automatic, can be eliminated while concurrently performing a demanding task, we reframe this phenomenon within the theoretical framework of the “attention set” (Most et al., 2005). Consequently, the specific prediction that cuing effects should reappear when feature dimensions of the cue overlap with those in the attention set (i.e., elements of the demanding task) was empirically tested and confirmed using a dual-task paradigm involving both sustained attention and attentional capture, adapted from Santangelo et al. (2007). Participants were required to either detect a centrally presented target presented in a stream of distractors (the primary task), or respond to a spatially cued target (the secondary task). Importantly, the spatial cue could either share features with the target in the centrally presented primary task, or not share any features. Overall, the findings supported the attention set hypothesis showing that a spatial cuing effect was only observed when the peripheral cue shared a feature with objects that were already in the attention set (i.e., the primary task). However, this finding was accompanied by differential attentional orienting dependent on the different types of objects within the attention set, with feature-based orienting occurring for target-related objects, and additional spatial-based orienting for distractor-related objects.

Exogenous attention can be counter-selective: onset cues disrupt sensitivity to color changes

In peripheral spatial cueing paradigms, exogenous attentional capture is commonly observed after salient onset cues or with cues contingent on target characteristics. We proposed that exogenously captured attention disrupts the selectivity to target features. We tested this by experimentally emulating the everyday observation that in a viewing situation in which the observer is monitoring a stationary display fort change to occur, the onset of a salient stimulus (onset cue) or a change in a stationary stimulus similar to the expected one (contingent cue) has a distracting effect. As predicted, we found that both types of cues reduced the target detection sensitivity but enhanced the bias to respond in a go-nogo-paradigm. With the onset cue, the sensitivity loss was more pronounced at the side of the cue, whereas the contingent cue affected both sides likewise. Moreover, the effects of the onset cue interacted with the task difficulty: the more selectivity a task required the more immune it was against disruption, but the more likely was a response. We concluded that onset capture disrupts selective attention by adding noise to the processing of the target location. The effects of contingent capture could be explained with cue-target confounding. Finally, we suggest a new model of attentional capture in which exogenous and endogenous components interact in a dynamic way.

Exogenous attentional capture by subliminal abrupt-onset cues: Evidence from contrast-polarity independent cueing effects.

In the present study, we tested whether subliminal abrupt-onset cues capture attention in a bottom-up or top-down controlled manner. For our tests, we varied the searched-for target-contrast polarity (i.e., dark or light targets against a gray background) over four experiments. In line with the bottom-up hypothesis, our results indicate that subliminal-onset cues capture attention independently of the searched-for target-contrast polarity (Experiment 1), and this effect is not stronger for targets that matched the searched-for target-contrast polarity (Experiment 2). In fact, even to-be-ignored cues associated with a no-go response captured attention in a salience-driven way (Experiment 3). For supraliminal cues, we found attentional capture only by cues with a matching contrast polarity, reflecting contingent capture (Experiment 4). The results point toward a specific role of subliminal abrupt onsets for attentional capture.

Distribution of attention modulates salience signals in early visual cortex.

Previous research has shown that the extent to which people spread attention across the visual field plays a crucial role in visual selection and the occurrence of bottom-up driven attentional capture. Consistent with previous findings, we show that when attention was diffusely distributed across the visual field while searching for a shape singleton, an irrelevant salient color singleton captured attention. However, while using the very same displays and task, no capture was observed when observers initially focused their attention at the center of the display. Using event-related fMRI, we examined the modulation of retinotopic activity related to attentional capture in early visual areas. Because the sensory display characteristics were identical in both conditions, we were able to isolate the brain activity associated with exogenous attentional capture. The results show that spreading of attention leads to increased bottom-up exogenous capture and increased activity in visual area V3 but not in V2 and V1.

Endogenous-like orienting of visual attention in rats

This study investigated the orienting of visual attention in rats using a 3-hole nose-poke task analogous to Posner, Information processing in cognition: the Loyola Symposium, Erlbaum, Hillsdale, (1980) covert attention task for humans. The effects of non-predictive (50% valid and 50% invalid) and predictive (80% valid and 20% invalid) peripheral visual cues on reaction times and response accuracy to a target stimulus, using Stimuli-Onset Asynchronies (SOAs) varying between 200 and 1,200 ms, were investigated. The results showed shorter reaction times in valid trials relative to invalid trials for both subjects trained in the non-predictive and predictive conditions, particularly when the SOAs were 200 and 400 ms. However, the magnitude of this validity effect was significantly greater for subjects exposed to predictive cues, when the SOA was 800 ms. Subjects exposed to invalid predictive cues exhibited an increase in omission errors relative to subjects exposed to invalid non-predictive cues. In contrast, valid cues reduced the proportion of omission errors for subjects trained in the predictive condition relative to subjects trained in the non-predictive condition. These results are congruent with those usually reported for humans and indicate that, in addition to the exogenous capture of attention promoted by both predictive and non-predictive peripheral cues, rats exposed to predictive cues engaged an additional slower process equivalent to human's endogenous orienting of attention. To our knowledge, this is the first demonstration of an endogenous-like process of covert orienting of visual attention in rats.

Top–down contingent attentional capture during feed-forward visual processing

Theeuwes (2010) summarizes an impressive number of studiesdemonstrating interference by irrelevant visual singletons in com-puter experiments with humans. In these studies, if participantssearch for a relevant singleton target, such as the single diamondamong circles (i.e., a shape singleton), an irrelevant singletondistractor, such as the single red circle among the green stimuli (i.e.,a color singleton), delays the correct response to the target (cf.Theeuwes, 1991, 1992). If this distractor – as was the case in therelevant experiments – does not predict the likely target position, it issaid tobeirrelevant.Theeuwes(2010)arguesthattheinterference bythe irrelevant distractor reflects stimulus-driven or exogenouscapture of attention by singletons or feature contrasts, which heassumes to occur early during the feed-forward phase of visualprocessing.According to this explanation, a stimulus initially capturesattention exogenously (i.e., in a stimulus-driven way) to its position,to the degree to which it is salient. Salience in turn is defined as thesummed local contrast in terms of color, luminance, and orientationdifference to the surrounding stimuli or the background (cf. Bergen J Itti & Koch, 2001). Theeuwes (2010) assumes that thissalience-driven capture of attention is fast and occurs within 150 mssince singleton onset, during the feed-forward phase of visualprocessing (cf. Lamme, 2003).In contrast to Theeuwes (2010), we think that top–downcontingent capture is the rule and explains initial and fast attentioncapture effects in the first feed-forward phase of visual processing.Duringa laterphaseand undersomeconditions exogenouscaptureofattention possibly follows. At the same time, we propose that theevidence presentedbyTheeuwesfails to supportexogenousorientingbecause it fails to exclude a top–down contingent capture explana-tion. We present our arguments in two sections. First, we review theevidence directly supporting ourclaim that saliencecapture is subjectto top–down control. From this evidence we derive the exogenous-capture criterion that must be met by experiments for demonstratingexogenousspatialattention,andshowthatthiscriterioninnotmetbythe studies reviewed by Theeuwes. Second, we review studiesshowing attentional capture by stimuli during the feed-forwardphase, and conclude that only top–down contingent capture but noexogenous-capture can be observed during the feed-forward phase ofvisual processing.1. The exogenous-capture criterionA number of visual search studies demonstrated that participantsexert top–down control over attentional capture (reviewed recentlyby Burnham, 2007). In the corresponding studies, the experimentersecures the participant's top–down control over attention bydeclaring a specific visual feature as defining the target, or at leastas being informative for finding the target. The amount of attentionalcapture can then be compared under two conditions: with stimulusfeatures (or feature contrasts) that match the search templates of theparticipants (i.e., their top–down control settings for attentionalcapture) and with stimulus features (or feature contrasts) that do notmatch the top–down control settings. In these studies, researchersinferred top–down control over attentional capture from stronger oreven exclusive attentional capture by stimuli with matching featuresor feature contrasts (cf. Bacon & Egeth, 1994; Folk, Remington, J Eimer & Kiss, 2008; Folk & Remington,1998).The finding that attentional capture depends on the matchbetween the attentional control settings and features of theattention-capturingstimulushasimplicationsfor proofsof exogenousattention, too. That is, from these studies follows that demonstratingexogenous or stimulus-driven attentional capture requires that norelevant task set to search for the attention-capturing feature orfeature contrast of a distractor stimulus exists (cf. Bacon & Egeth,1994; Folk et al., 1992). This is the exogenous-capture criterion.Importantly, the exogenous-capture criterion is not met by thestudies that have been reviewed by Theeuwes (2010).Thisisbecause all of Theeuwes' reviewed studies used singletons – astimulus which is salient on a particular dimension – as the relevant