Elsevier

Intelligence

Volume 38, Issue 1, January–February 2010, Pages 111-122
Intelligence

Lapses in sustained attention and their relation to executive control and fluid abilities: An individual differences investigation

https://doi.org/10.1016/j.intell.2009.08.002Get rights and content

Abstract

A latent variable analysis was conducted to examine the nature of individual differences in lapses of attention and their relation to executive and fluid abilities. Participants performed a sustained attention task along with multiple measures of executive control and fluid abilities. Lapses of attention were indexed based on the slowest reaction times in terms of both quintiles and the τ parameter from the ex-Gaussian distribution. It was found that the slowest, but not the fastest, RTs in the sustained attention task were related to a broad based executive control factor and a fluid intelligence factor. The results further suggested that only the working memory capacity and response inhibition sub-executive control factors were related to the slowest RTs, with the fluency measures not being related to any of the RT variables. The results are consistent with the idea that fluctuations or lapses in sustained attention, as indexed by the slowest responses, are related to executive control and fluid abilities.

Introduction

The ability to sustain attention has long interested researchers concerned with attentional processes in both basic and applied fields (Parasuraman & Davies, 1984). In particular, researchers have been interested in what happens when one cannot continuously sustain attention on a task leading to periodic lapses of attention (Reason, 1984). For instance, assume you are a baggage screener at a large international airport. Your job is to examine the contents of thousands of bags for the possible presence of illicit and dangerous materials. Clearly this task requires a great deal of attentional resources in order to sustain attention and detect possibly dangerous materials. Any momentary lapse in attention due to external stimuli (such as a crying baby) or internal thoughts (such as ruminating about a prior fight with your spouse) can lead to a failure to detect illicit materials with potentially hazardous consequences. Understanding these lapses of attention, whereby attention is disengaged from the current task and focused on other external distracting stimuli or internal thoughts (e.g., daydreaming), is important for understanding how and when attentional processes falter in both the laboratory and in real world situations. Therefore, in order to better understand lapses of attention in the present study we examined how lapses are related to a number of executive control and fluid ability measures.

Much recent work has been concerned with examining executive control requirements in a number of laboratory tasks and real world situations. Executive control refers to the set of general purpose control processes that regulate thought and action in a wide variety of situations. Executive control processes are of critical importance when novel responses have to be carried out in the presence of more habitual dominant responses (Roberts & Pennington, 1996). It is assumed that it is difficult to maintain attention on a task goal and therefore sustain attention on the task at hand when internal and external interferences and distraction are high (Engle & Kane, 2004). In situations when attention is tightly focused on the task goal, performance will be both fast and accurate. However, if attention is not tightly focused on the task goal, lapses of attention can occur which will lead to overall slower responses or to very fast errors that are guided by prepotent tendencies. For instance, consider the antisaccade task in which participants are required to fixate on a central cue and after a variable amount of time, a flashing cue appears either to the right or left of fixation (Hallet, 1978; see Everling & Fischer, 1998 for a review). With the onset of the flashing cue the participant's task is to shift their attention and gaze to the opposite side of the screen as quickly and accurately as possible. According to executive control views, it is critically important to maintain the task goal (“if flash on the left — look right”) in order to successfully perform the task given that the required response is directly opposite of the habitual response (i.e., looking at the flashing cue). Thus, any lapses in attention (or intention) will result in the prepotent response guiding behavior and hence the occurrence of a fast reflexive error (i.e., looking at the flashing cue; Unsworth, Schrock, & Engle, 2004).

A similar argument applies to the Stroop task. In this task participants are required to name the color in which color names are printed. When the color and the word match (e.g., Red presented in red ink), the task is quite easy. However, when the color and the word conflict (e.g., Blue presented in red ink), both reaction time and error rates increase. According to an executive control view, because the prepotent response conflicts with the task goal (e.g., “Say the color not the word”), a loss of goal maintenance (perhaps due to a lapse in attention) should result in the prepotent response guiding behavior and hence the occurrence of fast word naming errors or slower overall response times. Work by De Jong, Berendsen, and Cools (1999) supports this general argument. In this study, De Jong et al. had participants perform congruent and incongruent Stroop trials with either a long (2000 ms) or a short (200 ms) response-stimulus interval (RSI). De Jong et al. reasoned that the fast pace of the short RSI would keep attention tightly focused on the task goal, thereby preventing lapses. The long RSI, however, should induce more lapses as participants would have ample time between trials to think about things unrelated to the task at hand. Thus, De Jong et al. hypothesized that at the long RSI there would be a large Stroop effect, but the effect would be greatly attenuated with a short RSI. Interestingly, this is precisely what they found. With a short RSI the Stroop effect was a non-significant 11 ms. With a long RSI the Stroop effect was 47 ms. Furthermore, after rank ordering the reaction times (RTs) from fastest to slowest for each of the conditions and forming 10 separate bins, De Jong et al. found that the difference in the magnitude of the Stroop effect between the two RSI conditions was localized primarily in the slowest RTs. Specifically, in the fast paced condition, there were no differences between congruent and incongruent RTs at any of the bins. In the slow paced condition there were no differences between congruent and incongruent conditions in the fastest bins, but large differences in the slowest bins. De Jong et al. suggested that these results provide evidence for fluctuations in attention that occur on a trial-by-trial basis and lead to goal neglect (see also Kane and Engle, 2003, West, 1999).

Overall, this work suggests that if attention is not tightly focused on the task goal, lapses of attention can occur which will lead to overall slower responses. In terms of RT distributions this would lead to a large number of slow responses and an increase in the tail of the upper end of the distribution. Research consistent with this has examined overall RT distributions by either rank ordering RTs and placing them into separate bins (De Jong et al., 1999, Larson and Alderton, 1990) or by fitting an ex-Gaussian function to the overall RT distributions (West, 2001). The ex-Gaussian function is a convolution of an exponential and a Gaussian distribution which has been found to provide an accurate description of RT distributions and has been used as a tool in examining group and experimental differences in RT distributions (Ratcliff, 1979, Spieler et al., 1996). The ex-Gaussian has three parameters that describe the distribution: μ (the mean of the Gaussian), σ (the standard deviation of the Gaussian), and τ (the mean and standard deviation of the exponential). Although none of these parameters reflect an underlying cognitive process, research has shown that certain parameters are affected more by some manipulations than others and that group differences can be localized to specific parameters (e.g., aging, West, 2001; ADHD, Leth-Steensen, Elbaz King, & Douglas, 2000). Importantly, regardless of the method used for characterizing RT distributions, this work has suggested that there is something special about the slowest responses that seem especially vulnerable to manipulations of executive control and to deficits in executive control. In particular, this work has suggested that when demands for EC processes are high, there is an increase in the proportion of the slowest responses, but little change with the fastest responses (e.g. De Jong et al., 1999). Additionally, participants thought to have deficits in executive control also tend to differ from control participants primarily on the slowest responses (e.g., Leth-Steensen et al., 2000, West, 2001). Furthermore, work by Dinges et al. (Dinges and Powell, 1985, Dorrian et al., 2005) has found that sleep deprivation primarily impacts the slowest RTs with greater sleep deprivation leading to a large increase in the slowest RTs. As such this work suggests that these slow responses can be seen as providing an index of periodic lapses of attention which result from an inability of executive control processes to maintain or sustain attention on task goals.

Current neuroimaging work bolsters these notions by suggesting that lapses of attention, as indexed by the slowest RTs on various tasks, are linked to several brain areas typically associated with executive control. For example, a recent study by Weissman, Roberts, Visscher, and Woldorff (2006; see also Chee et al., 2008) examined fast and slow responses in a variant of a global–local task and found that the slowest responses were associated with lower activation in several areas thought to be associated with executive control. Specifically, Weissman et al. found that the slowest RTs were associated with reduced activity in the inferior frontal gyrus, middle frontal gyrus, and the anterior cingulate cortex prior to the onset of the stimulus. Weissman et al. argued that this reduced activity reflected a lapse of attention whereby participants were focusing on internal thoughts rather than the external stimulus prior to the onset of the trial. Like the De Jong et al. (1999) study this suggests that lapses of attention that occur in between trials can lead to performance decrements on the subsequent trial. Weissman et al. (2006) also found that the slowest RTs were associated with reduced activity in sensory processing areas of the occipital cortex suggesting that lapses of attention can lead to potentially lower quality perceptual representations. Finally, Weissman et al. (2006) found that the slowest RTs were related to increased activity in areas of the “default-mode” network (Raichle et al., 2001) which consists of brain regions that remain active between trials and during rest periods and are thought to be related to task irrelevant thoughts. Weissman et al. (2006) argued that this increased activity reflected task irrelevant thoughts (such as daydreaming) which lead to a lapse of the task goal and a subsequent decrement in goal directed behavior.

Additional neuroimaging work supports this. Mason et al. (2007) found that greater self-reports of mind wandering (i.e., lapses of attention) were related to greater activity in the “default-mode” network. Furthermore, Mason et al. (2007) found that activity in the “default-mode” network was positively correlated with a daydream frequency scale. Similarly, using the same sustained attention task as Dinges and Powell (1985) Drummond et al. (2005) found that the slowest RTs were associated with areas of the “default-mode” network and suggested that this increased activity in the “default-mode” network reflected instances of task disengagement and lapses of attention. Collectively these results suggest that the slowest responses seem to provide an index of lapses of attention which are related to reduced activity in executive control regions and increased activity in the “default-mode” network which lead to decrements in goal directed behavior.

Lapses of attention (as partially indexed by the slowest RTs) are not only important for understanding executive control more broadly, but are also important for understanding individual differences in executive control and their relation to other cognitive constructs. Specifically, one prominent view of executive control is the executive attention view of Engle, Kane, and colleagues (Engle and Kane, 2004, Kane and Engle, 2002, Kane et al., 2007b). This view primarily focuses on working memory capacity (WMC) as a construct responsible for the active maintenance of task goals in the face of interference. As such Engle, Kane, and colleagues have argued that measures of WMC such as Operation and Reading span tasks (Daneman and Carpenter, 1980, Turner and Engle, 1989) index individual variation in executive control (or executive attention). This view suggests that individuals low in WMC, and hence low in executive control, should be more prone to lapses of attention which should lead to poorer performance (increased errors and RTs) on a number of attention tasks. Support for this view comes from a number of studies which have demonstrated links between measures of WMC and other measures of executive control such as the antisaccade (Kane et al., 2001, Unsworth et al., 2004), Stroop (Kane and Engle, 2003, Long and Prat, 2002), and flanker (Heitz and Engle, 2007, Redick and Engle, 2006) tasks.

Accordingly, by this view one would expect that measures of WMC and other cognitive abilities should be related to the slowest, but not the fastest, RTs. In fact, work in intelligence has suggested that the slowest RTs typically correlate higher with measures of intelligence than the fastest RTs leading to a worst performance rule (see Coyle, 2003 for a review). In an early and classic study of the worst performance rule, Larson and Alderton (1990) found that the correlations between RTs on a choice RT task and composites of WMC and intelligence increased from the fastest to the slowest RTs. Thus, the slowest and the worst trials correlated the best with composites of WMC and intelligence. Very much in line with the work discussed above, Larson and Alderton (1990) suggested that the slowest trials represented momentary lapses in working memory, and those individuals who tended to have the most lapses also tended to perform poorly on the measures of WMC and intelligence. Further support for the notion that the slowest trials are more related to measures of WMC and intelligence than the fastest trials comes from a recent study by Schmiedek, Oberauer, Wilhelm, Süß and Wittmann (2007). In this study, RT distributions from multiple choice RT tasks were desribed with the ex-Gaussian function and it was found that the τ parameter (which characterizes the slowest RTs) was substantially related to both WMC and measures of fluid intelligence (gF). Like the Larson and Alderton (1990) study, these results suggest that the slowest and worst trials are related to both WMC and intelligence.

Based on an executive control and lapses of attention view these results suggest that individuals differ in their ability to maintain task goals in working memory in order to sustain their attention on a task. Any momentary lapse of attention due to a strong external stimulus or due to distracting internal ruminations will lead to a delayed response in very simple RT tasks. Additionally, Kane et al. (2007), Kane, Conway, Hambrick and Engle (2007) recently suggested that individual differences in mind wandering based on self-reports in an experience-sampling study were strongly related with measures of WMC, especially during challenging tasks. Furthermore, McVay and Kane (2009) recently demonstrated that rates of mind wandering partially mediated the relation between WMC and sustained attention. Thus, individual differences in lapses of attention or mind wandering (see Smallwood & Schooler, 2006 for a review) as indexed by either the slowest RTs in basic RT tasks or self-report measures seem to be strongly related to measures of WMC and intelligence. As such, this suggests that the ability to actively maintain task goals and prevent lapses of attention or mind wandering is an important cognitive construct which should be related to other measures of executive control and cognitive abilities.

The aim of the present study was to examine the relation between measures of executive control, fluid abilities (gF), and lapses of attention. As noted above, previous work has shown that the slowest RTs in several basic RT tasks are related to both WMC and gF. However, no study has examined the extent to which these slow responses are related to executive control more broadly. In particular, although measures of WMC provide a good index of executive control, they are not the only measures of executive control. As such, it is important to examine how the slowest RTs are related to other measures of executive control. In particular, based on the preceding discussion of the importance of goal maintenance and the prevention of lapses in response inhibition tasks like the antisaccade, flankers, and Stroop, one would expect that the slowest RTs should be related to performance on these tasks. Thus, the goal of the present study was to examine how executive control processes indexed by a variety of tasks (including measures of WMC, response inhibition, and fluency) would be related to lapses of attention in a sustained attention task. To do so, we utilized the psychomotor vigilance task (PVT; Dinges & Powell, 1985) that has been used previously to examine sustained attention. Previous research has shown that RT increases with time on task as does the number of lapses (Dinges & Powell, 1985). Additionally, as noted previously, factors such as sleep deprivation tend to amplify these effects (Dorrian et al., 2005) and the slowest RTs in this task have been found to be linked to greater activity in the “default-mode” network (Drummond et al., 2005). Thus, there is good evidence that the slowest RTs in this task provide an index of lapses of attention as discussed throughout. In order to examine the fastest and slowest RTs we utilized two different methods that have been used previously. First, each individual's RTs were ranked from fastest to slowest and placed into quintiles and the mean of the quintiles were correlated with the executive control and gF measures. Next, each individual's RT distributions were fit with the ex-Gaussian function and the resulting parameter estimates (μ, σ, and τ) were correlated with executive control and gF measures.

Using this sustained attention task and these methods for characterizing RT distributions, a latent variable analysis was conducted examining the relation between the slowest RTs and measures of executive control and gF. Specifically, examining the three separate executive control factors, it was expected that only the WMC and response inhibition factors should be related to the slowest RTs, while the Fluency factor would not. This is because both the WMC and response inhibition factors are represented by tasks that have a high demand for active maintenance whereby any lapse in attention could be detrimental to performance. The fluency tasks, however, primarily rely on controlled retrieval from long-term memory and thus, should be hurt less by lapses of attention. This would provide both convergent and discriminant validity for the notion of lapses of attention. As such the current study provides a unique contribution to this field in that it examines lapses in attention in a well established sustained attention task and how these lapses are related to executive control abilities.

Section snippets

Participants

Participants were 151 individuals recruited from the University of Georgia subject-pool. Participants were between the ages of 18 and 35 and received course credit for their participation. Participants were tested individually in a laboratory session lasting approximately two hours.

Procedure

All participants completed (in order) operation span, reading span, antisaccade, category fluency, the psychomotor vigilance task, letter fluency, arrow flanker, Raven, verbal analogies, and Number Series.

Psychomotor vigilance task (PVT)

The

Experimental effects

First, sustained attention effects in the psychomotor vigilance task were examined. RTs were grouped into eight blocks of ten trials each. Shown in Fig. 1 are the resulting RTs. Consistent with previous work (Parasuraman, 1986, Kribbs and Dinges, 1994), RTs increased as a function of time on task indicating a vigilance decrement, F(7, 1050) = 51.44, MSE = 1580.62, p < .01, partial η2 = .26. Specifically, RTs increased on average by 64 ms from Block 1 to Block 8 and this increase was significantly

General discussion

The goal of the current study was to explore lapses in sustained attention and their relation to executive and fluid abilities. It was shown that indices of lapses of attention were related to both executive and fluid abilities. Specifically, it was shown that lapses of attention, indexed by the slowest quintiles and the τ parameter after fitting an ex-Gaussian function to the distributions, were related to overall executive control and gF factors. These results provide evidence that in the

Conclusion

The current findings suggest that individual differences in lapses of attention were related to both executive and fluid abilities. It was demonstrated that the slowest, but not the fastest, RTs indexed by both the slowest quintiles and the τ parameter from the ex-Gaussian distribution were related to executive control and fluid abilities consistent with the worst performance rule. Furthermore it was shown that not all executive control functions were related to the slowest RTs. Specifically,

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