Executive-function vs. Executive-failure theories of mind wandering

     This blog focuses on the discourse between Smallwood & Schooler (2006), McVay & Kane (2010), and Smallwood (2010), in which two compelling theories of mind wandering are juxtaposed in order to address the advantages and potential flaws of each.

Smallwood and Schooler (2006) present an executive-function theory, in which they suggest that mind wandering results from the automatic activation of control processes, causing attention to shift away from the task-relevant external environment, and instead towards personally-relevant goals.  Mind wandering, in this viewpoint, is caused by the activation of unresolved goals (also called current concerns).  Tasks that therefore rely on control processing should cause a suppression of mind wandering.  When the mind does wander, one’s ability to coordinate task-relevant information into awareness will be impaired as the necessary control processes are directed elsewhere.  In other words, consciousness becomes decoupled with the external task environment and instead is coupled with internalized processes.
       In direct response to the theory suggested by Smallwood & Schooler (2006), McVay & Kane (2010) instead propose an executive-control failure theory of mind wandering, in which, unlike the executive-function theory, mind wandering does not rely on the same executive control resources allocated towards the present task. Instead they argue that mind wandering is the result of a failure of executive control over task-irrelevant thoughts. While both of these theories suggest that the content of mind wandering thoughts consists of present, urgent, and task-irrelevant goals, in the executive-failure theory, these thoughts occur only when the executive control system fails to defend against them.  This difference between the two theories is critical to understand how each has very different implications in relation to the processes of mind wandering.

       It does seem that the executive-failure theory is better at explaining evidence of individual differences as well as findings found in studies involving alcohol intake as well as disorders like ADHD.  ADHD is associated with deficits on executive-function tasks.  Those diagnosed with ADHD show increased reports of TUTs compared to healthy controls.  It is postulated that if the executive-function theory were true then the deficits in executive functions would cause a decrease in TUT propensity compared to controls, given that the same resources for executive-function tasks (which show deficits) would be needed for mind wandering.  Therefore, this data would seem to directly contradict the executive-function theory.  However, is it possible that those with ADHD show deficits on executive-function tasks because they mind wander more?  In other words, compared to normal subjects do individuals with ADHD just more readily devote their resources to mind wandering?  If so, these findings would not only fail to contradict the executive-function theory, but would also help explain why these deficits on executive-function tasks occur for those with ADHD.  Depending on the proportion of resources devoted to mind wandering, this deficit could be the result of a higher propensity of those with ADHD to attend more strongly to mind wandering than controls not because of a significant lack of executive resources but rather the way in which they prioritize where to allocate them.  

        McVay & Kane (2010) encounter a slight problem while trying to explain results of studies looking into aging, as older adults have been found to report less mind wandering than younger adults, despite the fact that older adults have more executive control deficits than younger adults.  In order to account for this discrepancy, the researchers introduce a second factor—the current concerns theory—in which they argue that older adults have fewer concerns during testing and, therefore, report less mind wandering than younger adults.  This seems like an unsupported conclusion to explain these findings, and the results actually support the executive-function theory quite well, which causes me to question this explanation further.

       Neuroimaging has offered some important insight into the functionality of mind wandering, implicating brain regions mainly associated with executive control.  fMRI studies have shown that the default network regions are significantly more activated prior to reports of mind wandering compared to activation prior to reports of being “on-task” (Christoff et. al, 2009). This finding that the default network regions are employed more during mind wandering episodes offers support of the executive-function theory through a measure based on more than just self-report. In addition Christoff et al. compared activation of these regions during mind wandering with and without meta-awareness (see Figure 4).

Figure 4

These images show that there is more activity in these default regions when subjects are unaware of mind wandering, compared to during states of meta-awareness.  This raises problems in light of the executive-failure theory.  McVay & Kane try to reconcile why there might be more activation during mind wandering without meta-awareness by suggesting that such activation may reflect one’s effort to refocus on the present task and that conscious awareness is not needed for this refocusing to happen. Not only does this seem unlikely, but the researchers also ultimately do not offer any reasoning as to why this might be the case.  McVay & Kane’s lack of explanation, in addition to the activation visibly seen in the fMRI images, cause me to lean further in favor of the executive-function theory of mind wandering.  Additionally, I think that the increase in eye movement during meta-awareness (self-caught) compared to mind wandering without meta-awareness (probe-caught), in eye-tracking studies reflects the subjects’ attempts to refocus on the task at hand. If so, then this refocusing during a state of meta-awareness would refute McVay & Kane’s claim. 
     In light of mind wandering research findings since 2006, Smallwood (2010) explains and re-articulates the claims made by Smallwood & Schooler (2006) that McVay & Kane (2010) argue against.  Smallwood assumes the position that, because mind wandering is a conscious, reportable state, implies that it is globally available to the system and therefore does demand resources.  While the executive-failure theory explains mind wandering during difficult tasks, unlike this global availability hypothesis, it fails to do so across all contexts.  More specifically, while the executive-failure theory is promising in relation to keeping unwanted thoughts out of the mind, it is not as firmly supported when explaining mind wandering in relatively easy, nondemanding tasks where thoughts are most likely not “unwanted,” as such thoughts may actually be advantageous for planning and creativity.  While the cognitive failure theory may be applicable during demanding tasks, in which mind wandering does result from a failure in proactive maintenance of task-relevant environment, Smallwood (2010) argues that this would occur within the context of the executive-function theory because mind wandering itself is a conscious process.

      Based on these articles and the evidence provided, the executive-function theory seems to support the majority of these lapses found in mind wandering research, though further research is needed to address the discrepancies which have been found (e.g. the ADHD studies previously mentioned). Within the executive-function theory approach, it is important to note the paradox of mind wandering itself, as decoupling from one’s present environment is detrimental to current task goals, while the coupling with internalized goals that results may provide important cognitive benefits in regards to planning and creativity.