EXECUTIVE FAILURE VS. EXECUTIVE FUNCTION

Mind wandering is a common phenomenon in everyone’s daily lives. Thinking about lab during molecular biology class. Thinking about this blog post during antibody incubations. Thinking about sleep at 5:30am…okay, this might be due to fatigue. Yet, the exact mechanisms that account for mind wandering remains inconclusive. However, there are two prominent and competing views on mind wandering, namely the “executive function” and the “executive failure” views of mind wandering. In this post, we will examine both viewpoints in detail, beginning with a description of the key components of each viewpoint, followed with a comparative analysis on the similarities and conflicts between the two camps. Later on, in a questions and comments section, we discuss the evidence for and challenges against each theory. Upon consideration of both evidence and challenges, we proceed to choose the most compelling theory. Finally, we conclude with a section on links of these two theories to neuroscience and possible future experiments.

Summary and Comparative Analysis  

Before we delve into a discussion of the evidence for and challenges against the two models of mind wandering, it is important to first establish what the “executive function” and “executive failure” models entail. Thus, below, we provide a description of both theoretical viewpoints, including key components of each theory. Subsequently, we examine the fundamental conflict between these two viewpoints in a comparative analysis.

Executive Function

Conceived and detailed by Smallwood and Schooler in 2006, the “Executive Function” model argues that mind wandering utilizes executive resources and thus reduces the amount of executive resources available for the primary task at hand (Smallwood & Schooler, 2006; McVay and Kane, 2010). This view falls into the “resource theory” category in that it espouses the view that there exists a limited pool of executive resources responsible for information processing and attention (and lack thereof). As Smallwood et. al. notes, “When mind wandering occurs, the executive components of attention appear to shift away from the primary task, leading to failures in task performance and superficial representations of the external environment.” Importantly, the executive function viewpoint also maintains that mind wandering “can be seen as a goal-driven process, albeit one that is not directed toward the primary task” (Smallwood, 2006) and thus performs an executive function.

Executive Failure

In response to Smallwood and Schooler’s 2006 study, McVay and Kane proposed an alternative model on mind wandering that generally agrees with but extends upon Watkins’ control theory. Specifically, they argue mind wandering is a result of “a failure of executive control over automatically (and continuously) cued thoughts rather than as consuming executive resources.” (McVay and Kane, 2010) in their “control failure x concerns perspective” on mind wandering. In direct contrast to Smallwood and Schooler, McVay and Kane contends that mind wandering “does not draw on the same executive resources as executive control,” and thus can be controlled or prevented using the “executive–control system.” Ultimately, this viewpoint holds that mind wandering reflects a failure in executive control and serves no useful function.

Comparative Analysis: The Conflict and the Conversation

I found this week’s papers particularly interesting because they responded directly to each other and thus allowed for a conversation on the key questions in each paper. Thus, in this comparative analysis, we will examine the key points in this conversation.  The conflict between these two viewpoints is clear: one theory holds mind wandering consumes executive resources and may serve functional roles in daily life whereas the other model contends that mind-wandering is a result of executive failure and does not consume the same executive resources as the primary task. At first glance, this seems like a lost case; how can you ever reconcile two completely opposite viewpoints? Smallwood (2010) again stepped up to the task in his “Reply to McVay and Kane.” In response to MacVay and Kane’s contention that mind wandering is a result of control failure, Smallwood argues that despite the possibility of mind wandering happening after control failure, it nevertheless is “always a conscious reportable experience and so is globally available to the system.” He continues to argue that this global availability suggests that mind wandering demands resources, in accordance with his executive-function viewpoint. The most striking point in this conversation was not the different viewpoints, but their potential semi-coexistence. Specifically, I was surprised that Smallwood (2010) defended his viewpoint by introducing a completely new concept, namely global availability. What I found most compelling about Smallwood’s reply was the consistency of his “global availability hypothesis” with the key features of McVay and Kane’s model. However, as will be addressed in the next section, I found the concept and introduction of the global availability hypothesis somewhat arbitrary. Even more concerning, I found the assumptions associated with the “global workspace” quite severe.

Questions and Comments

The Evidence and Challenges

There exists robust evidence both for and against these two theories on mind wandering. Let’s begin with the Executive Function theory elaborated by Smallwood and Schooler. If mind wandering does indeed utilize executive resources, then this model would predict an inverse correlation between mind wandering and performance on the primary task. This is exactly what several studies found. As the authors note, “the evidence presented in this section suggests trade-offs between mind wandering and task performance.” Specifically, mind wandering was also inversely correlated with the difficulty of the primary task, which would also support a resource theory approach. If mind wandering utilizes executive resources, and assuming that more difficult tasks exhaust more resources, tasks that are more difficult and thus demand more resources would leave less available resources for mind wandering. Even more pressingly, evidence exists to show that mind wandering actually competes for working-memory resources; specifically, impairments (slight, but present) in task efficiency are observed in the presence of mind wandering. The observation that mind wandering interferes with the “successful completion of nonautomated task” suggests that mind wandering requires working memory and executive resources.

However, although evidence clearly exists to support the executive function viewpoint, I have several concerns with the way in which the evidence was collected and the way mind wandering is defined. For instance, much of the results discussed here rely on self-reports and questionnaires. This runs into the exact same problem that we discussed in last week’s blog post, namely a lack of consistency. Without a rigorous definition of mind-wandering, the authors of these studies risk invalidating their results. Specifically, subjects can choose to not report TUITs or may not catch slight instances of TUITs. Furthermore, the conception of what constitutes “mind wandering” may be different among subjects, which serves as a further possible confounder of the results. Furthermore, I found the meta-analysis of the evidence a bit troubling. Although I know that this happens very often in research and can be very enlightening, I think it is important to have normalization procedures in place when one does such an analysis. For instance, Smallwood cites evidence from several different times of studies, from SART studies to text comprehension. However, he did not dwell upon the possibility that evidence from across such different studies may require further processing before they could be compared to each other.

In reply to Smallwood’s 2006 paper, McVay and Kane (2010) provides evidence for a control failure model of mind wandering. In accordance with this theory, mind wandering should be prevented when “control is proactively initiated and maintained” in response to task demands. Importantly, they distinguish between two types of executive control, namely proactive and reactive, that are dissociable by behavioral measures and association with different brain areas. The majority of the evidence for McVay and Kane stems from studies done utilizing individuals with differences in their propensity to mind wander. Specifically, the authors provide what they believe to be counter-evidence for Smallwood and Schooler (2006)’s executive function theory. They argue that if mind wander indeed demands executive resources, then individuals with more resources (namely high working-memory-capacity individuals) should exhibit more mind wandering than low working-memory-capacity individuals. However, they found the opposite effect: subjects with higher WMC clearly demonstrated greater executive control and less frequent mind wandering across tasks. The authors argue that this evidence serves to counteract the executive function resource theory presented by Smallwood and Schooler (2006). Furthermore, the authors cite the default network to provide evidence for their executive failure theory. The default network is essentially a collection of different regions in the brain are implicated in mind wandering (found to be especially active during mind wandering). The authors reference the neuroimaging results from Weissman et. al. (2006), which found trade-offs between control areas of the brain and the default network. Specifically, reductions in PFC activation, which was interpreted to be reductions in attention-control area activity, “reliably predicted lapses of attention” (McVay and Kane, 2010). The authors cite this “anti-correlation” between default network activation and executive network activation as evidence for their view that executive control failures are responsible for mind wandering.

There are several clear problems with the strategy presented above. Specifically, the association of the prefrontal cortex with exclusively proactive executive control and the anterior cingulate cortex with exclusively reactive executive control provide an oversimplification of the functions of the PFC and ACC. Although the association may definitely be present, there is no definite engram, and no particular region of the brain is exclusively responsible for one task. Furthermore, there are clear alternative explanations for PFC activation that were not considered in the studies mentioned. Thus, one cannot make any decisive conclusion without proper controls, which were also not described in the papers. Furthermore, I found the association of working memory capacity (WMC) with executive resource capacity very troubling. McVay and Kane (2010) essentially utilize WMC as a proxy for the amount of executive resources an individual has at his/her disposal. Although working memory capacity definitely counts as an executive resource, it is not the only such resource, and a higher working memory capacity does not necessarily imply the existence of greater executive resources. Lastly, I found the authors’ discussion of the default network as evidence particularly troubling. Again, the utilization of PFC activation as a proxy for executive control without the proper controls impinges severely upon the validity of their data. Furthermore, the conclusion they drew from the results was also ungrounded. Indeed, the trade off between “executive” areas of the brain and the default network could provide evidence for the very hypothesis McVay and Kane (2010) are trying to disprove, namely the executive function hypothesis. One can interpret this observed “trade off” as an indication that mind wandering utilizes executive resources, thus leading to lower activation rates in the executive areas of the brain (corresponding to a higher level of activation in the default network). Thus, the evidence presented has clear flaws.

The Choice

After evaluating Smallwood’s original resource theory centered executive function viewpoint, McVay and Kane (2010)’s evidence, and Smallwood’s reply, I must say that I am leaning towards the executive function viewpoint. However, this is only in light of the evidence presented for each theory and the qualifications the respective authors mentioned. On a psychological level, however, I don’t think either theory really tells the whole story. Rather, I think a hybrid of these two theories would make for a complete description of mind wandering. Executive function and executive failure models need not be completely mutually exclusive, as Smallwood implied in his 2010 paper. Just as different types of mind wandering exist (recall Giambra defined at least two: directed mind wandering and involuntary mind wandering), I believe different mechanisms behind mind wandering also exist. For instance, executive function may account for mind wandering during certain conditions, such as those in which mind wandering is beneficial for adaptation or creativity purposes, whereas mind wandering could be due to executive failure in other situations. I would be very interested to see further investigation into this topic matter and especially the introduction of a hybrid theory.

Links to Neuroscience
 

Okay, after my rant on McVay and Kane (2010)’s assumptions in their neuroimaging evidence, it’s clear that I think it’s very difficult to biologically evaluate these two theories. Don’t get me wrong, though; I think neuroimaging provides extremely valuable data. The key is in the interpretation of the neuroimaging results; correlation studies are both insightful and conducive to future studies. However, one just needs to be careful to not form causal relationships on the basis of correlational studies. In addition to neuroimaging studies, however, I think it would be interesting to have a mouse model of these two viewpoints. For instance, the researcher could create two separate populations of mouse, with the experimental group being deficient in executive resources. One way to accomplish this could be silencing a key pathway that is known to be important in information processing. Furthermore, one could also create a third group of mice with working memory deficits. We can then train these mice to perform a specific task, and task efficiency could be evaluated across populations to see if a difference exists between mice with access to different degrees of executive resources. Furthermore, we could also compare the WMC deficient mice with the executive resource deficient mice to see if the former’s task efficient accurately predicts that of the latter. However, several hurdles must be first overcome before this could be realized. For one, a pathway that is critical to information processing needs to be defined and results need to be accurately controlled for. Given the appropriate controls and experimental design, I think this study could be very enlightening!

References

Smallwood, J. and J. W. Schooler (2006). The restless mind. Psychol Bull 132(6): 946-958.2

McVay, J. C. and M. J. Kane (2010). "Does mind wandering reflect executive function or executive failure? Comment on Smallwood and Schooler (2006) and Watkins (2008)." Psychol Bull 136(2): 188-197; discussion 198-207.

Smallwood, J. Why the global availability of mind wandering necessitates resource competition: Reply to McVay and Kane (2010). Psychological Bulletin, Vol 136(2), Mar

2010, 202-207

Image References

Got Questions? http://www.victesolin.ca/imported-20101026012429/2011/1/12/got-questions.html Accessed 02/27/2013

National Geographic. Daily News. http://news.nationalgeographic.com/news/2010/07/100701-science-animals-mating-mice-mouse-aphrodisiac-tears/ Accessed 02/27/2013

Illustration Source. http://www.illustrationsource.com/stock/image/247949/an-illustration-of-a-woman-arriving-at-a-crossroads/?&results_per_page=1&detail=TRUE&page=9  Accessed 02/27/2013.

MIND WANDERING AND META-ATTENTION

Day-dreaming, fantasizing, and other forms of mind wandering constitute 30% of our daily lives, according to Reichle et. al., and thus have naturally attracted a great deal of attention in the psychological field. In today’s post, we will examine four studies on mind-wandering, and more specifically, their views and proposed models on the factors that contribute to mind wandering as well as the balance between exogenous and external contributors. We begin with a summary of these studies, with particular focus on their primary point of view/proposed model and a description of their key methods. We will also address some of their key findings and the implications of those findings. Afterwards, we move on to a comparative analysis of these studies, in which we will point out key parallels and distinctions between the proposed models/points of views as well as integrate ideas from the different studies. A questions and comments section will follow, in which we revisit the methods employed and examine whether they’re sufficient in addressing the questions asked. We will also suggest alternative approaches that may more fully address the questions or just provide a different avenue of investigation into these questions. Lastly, we will conclude with an examination of the links between these studies and neuroscience.

Summary of Studies

Antrobus, J.S. et. al. (1966)

Antrobus’ seminal 1966 study on streams of consciousness, or task-irrelevant events (let us call these TIEs from henceforth), describes a model for relating the relationship between generation of TIEs to one’s response to external stimuli. Antrobus’ model is one of information processing and thus centers upon the assumption that a Central Executive with limited resources is responsible for processing both endogenous and external information. Thus, under conditions of high demand from external stimuli, production of TIEs will be diminished as the Central Executive must focus its resources on responding to the external stimuli. Similarly, under conditions of high demand from internal stimuli, production of TIEs will also be diminished according to this model. To test this hypothesis, Antrobus performed three experiments in which he altered the external and internal demands and examined the corresponding production of TIEs. More specifically, he examined the impact of short-term memory load (by increasing signal rate in signal detection tasks), financial reward, and distressing information (by showing the subjects a fake radiocast describing imminent war between China and the US) on the probability of TIE generation. The researchers found increasing speed of signal presentation or demands on short-term memory led to reduced reports of TIE generation. Similarly, in the second experiment, graded financial award also led to a decrease in TIEs whereas subjects given the distressing information prior to the tasks exhibited increased TIEs.

Giambra, L.M. et. al. (1995)

            Giambra et. al. came up with a laboratory method for studying Task-unrelated images and thoughts (TUITs). We will think of these as the equivalents of the TIEs described earlier. He contends that TUIT production occurs when external stimuli imposes a relatively low cognitive demand; the excess cognitive capacity is utilized to generate TUITs. As Giambra (1995) puts it, “…TUIT occurrence and unused capacity, when performing a task, are directly proportional.” Interestingly, and as a departure from Antrobus’ study, Giambra notes that there exist more than one method of TUIT generation: as the result of one’s conscious attention shift and involuntary shifts of attention. In the former case, the TUIT is described as “more compelling” than the task at hand and controlled by higher centers in the brain. On the contrary, the latter case is described as involving lower orders of control and information-processing as they are not “motivationally determined.” To test his resource theory centered hypothesis, Giambra conducted two experiments; in the first experiment, subjects performed a vigilance task that allowed for “the expression of a wide range of TUIT propensities.” Results indicated that vigilance tasks can provide reliable measures of TUITs. The second experiment examined the “stability of TUIT likelihood differences.” Giambra et. al. found that TUIT generation was shown to be dependent on aging, hyperactivity, time of day, and level of depression.

Teasdale, J.D. et. al. (1995)

Teasdale followed up with a study that indicated stimulus-independent thought (SITs) depends on central executive resources. Specifically, he agrees with several aspects of Antrobus’ study, most prominently the resource theory centered theory. Teasdale supports the view that a Central Executive with limited resources is responsible for information processing and generation of SITs. It is important to note that Teasdale adopts the Baddeley-Hitch description of working memory, which consists of three components: a central executive and two peripheral systems, namely the visuospatial scratchpad and the loop-phonological store system. To investigate the role of each component in the generation of SITs, Tesasdale et. al. performed four experiments using the interference methodology. Specifically, subjects performed a task with interventions designated specifically to correlate to each of the three working memory components, as described by Baddeley-Hitch. Experiment 1 focused on the phonological loop and experiment 2 focused on the visuospatial sractchpad.  Results indicated no significant differences between the control and experimental groups in the generation of SITs, thus suggesting that their generation is not dependent on the phonological loop or the visuospatial scratchpad. Experiments 3 and 4 focused on the central executive and results indicated that generation of SITs was dependent on central executive resources.

Reichle, E.D. et. al. (2010)

Reichle et. al. did an interesting variation on the mind wandering theme: he tracked and compared eye movements during normal and mindless reading. Specifically, he defines “mindless reading” as “ when the eyes continue moving across the page even though the mind is thinking about something unrelated to the text” (Reichle, 2012). This study investigated both local and global eye movement patterns in both self-caught and probe caught mindless reading. Method wise, Reiche et. al. monitored the gaze location of the participants’ right eye during reading (an excerpt from Sense and Sensibility) using an EyeLink 1000 eye tracker. Participants reported “zoning out” 8 to 36 times during the excerpt. Even more interestingly, analysis of participants’ eye-movements indicated that fixation duration is longer during mindless reading and fixations were also less affected by “lexical and linguistic variables” than fixations in non-mindless reading. There were more off-text fixations during the probe-caught mindless reading than normal reading and self-caught mindless reading. Furthermore, eye-movements immediately before “self-caught” mindless-reading were also very erratic, even compared to those in probe-caught mindless reading.

Comparative Analysis

I found this weeks’ papers especially interesting both because of their subject matter but also in the ways that they relate to each other. Specifically, relative to the papers from previous weeks, this week’s papers represent a set of the most harmonious/least-contested viewpoints. Whereas previous weeks’ papers featured papers with polar opposite viewpoints on a given issue, this week’s papers offer similar viewpoints, though with important variations (and naming systems…). Indeed, all three papers echo the idea of a central executive system that has limited resource and information processing capacity in some way. Antrobus (1966) directly references this as being responsible for information processing: “Under most conditions of moderate activation and wakefulness we may postulate that the external stimuli have a somewhat greater priority for processing by a Central Executive.” Giambra (1995) also echoes this idea in his study; indeed, he notes “TUIT occurrence and unused capacity, when performing a task, are directly proportional.” For Giambra, however, it is the left over cognitive capacity of the central executive during an undemanding task that is used for the production of TUITs. Similarly, Teasdale (1995) articulates “stimulus-independent thought depends on central executive resources.” Thus, clearly, the authors for this week are in agreement about the existence of an information processing central executive that is critically involved in the generation of mind wandering. Despite the similarities of the authors’ viewpoints, however, there were some important differences, in both their inferences and methodologies, most of which will be covered in the next section. For instance, whereas Antrobus was focused primarily on daydreaming, Giambra (1995) was interested in several forms of TUITs. Furthermore, whereas Antrobus assigned the label “daydreaming” to account for any mind wandering exhibited by the participants, Giambra took account the possibility of different types of TUITs with different origins and processing centers. I found this insight to be very enlightening, although I do feel that more definitive experiments need to be done to support this theory.

Questions and Comments: Methods, Revisited and Alternative Explanations

 The most concerning problem I had with this weeks’ papers were the methods and result interpretation. While I think the research topic is extremely fascinating and the questions clearly relevant to daily life, I feel that many of the methods employed were insufficient in addressing the question and that the results could have been interpreted in a more rigorous manner. For instance, Antrobus (1966) relies on participant reports of daydreaming and mind wandering as a key portion of his result. This approach poses obvious problems as participants can have different interpretations of “daydreaming.” While some may consider daydreaming just slightly “zoning out,” another may consider it to mean completely detaching from the task at hand. Thus, without a strict and enforced definition of daydreaming, the reports cannot be consistent. Furthermore, the fact that the reports are exactly that—self-reports—also raises several problems. Participants can choose not to report daydreaming instances or may over-report daydreaming instances in the absence of a strict definition of daydreaming. Furthermore, I felt that the result interpretation of experiment 2 (involving the financial reward and penalty) was partially unsubstantiated. For instance, he found a payoff effect (participants in the group with the highest financial penalty); however, this was only the case for the male participants, as indicated by graph 2. He explains this by “perhaps the reward for mastering the task and satisfying E’s instructions overrides the monetary payoff, particularly for high-achieving college girls.” Yet, this is not substantiated by any experiment and seems almost like a second thought. The graphs below show these results; graph 1 shows the payoff effect and graph 2 shows the same “effect” for the male and female participants.

Giambra (1995) et. al. went one step beyond Antrobus’ original study by accounting for two types of TUITs: those to which subjects consciously switch attention and those that subjects involuntarily arrive at. He posits that the former is more compelling than the task at hand and is processed by higher order brain centers and that the latter is processed by lower brain centers. I found this rather illuminating because it takes into consideration the relative excitement level between the task at hand the TUIT. Furthermore, it also harks back to the vigilance decrement that we covered in previous classes. In particularly monotonous tasks, perhaps the subject experiences a vigilance decrement as a result of TUITs formation, or visa versa? It’s definitely an interesting possibility to explore. However, Giambra (1995) also falls prey to the same self-reporting utilized by Antrobus. Subjects are asked to press a button every time they experience task-unrelated thoughts. This poses a clear problem because of the reasons discussed above. Reichle (2010) solves this problem in his study on mindless reading by utilizing probes to detect mindless reading. The incorporation of probe-caught mindless reading in Reichle (2010) was very compelling; even more compelling was his comparative analysis of probe-caught and self-caught mindless reading. In this way, he can not only provide a more accurate and consistent report on the mindless reading, he can also provide a reliable description on the “accuracy” of self-reports by analyzing the overlap between self-caught and probe-caught mindless reading. However, as compelling as I found Reichle’s study, I did have one important concern with it: it only had four participants!! While I felt the general experimental design of the study was very well done, four participants is nowhere near enough to make a conclusion. It is a good start for sure, but a larger scale study must be done first to truly substantiate his contention. I also found this to be a similar problem in Antrobus’ 1966 study as well as Giambra’s 1995 study. With so few participants, a few outliers would be sufficient to skew the data and confound the results, especially in the presence of such uncontrolled factors such as self-reporting.

         
Links to Neuroscience and Future Directions

I think it would extremely interesting to translate some of the studies discussed in this weeks’ papers into neuroscience experiments. For instance, I brought up the possibility that self-reports may not always be accurate or consistent. A possible way of testing this and of providing a more consistent bar for mind wandering could be to have the subjects perform similar tasks while inside an fMRI machine. This way, we could monitor the dynamic and changing brain activation patterns during focused task performance as well as during mind wandering. Furthermore, we can compare verbalized self-reports with fMRI activation and deactivation patterns to determine whether a strong correlation exists.  Clearly, the subject would have to remain perfectly still for a prolonged period of time, and the consequences of this would have to be taken into account during result analysis. Other less restrictive forms of brain imaging could also be employed. It is important to remember, however, that this provides a global view of brain activation and deactivation patterns during mind wandering. It would be interesting to the biological realm and try to identify physiological changes associated with mind wandering (such as a reduced heart rate, etc.)

References

Antrobus, J. S., J. L. Singer (1966). Information theory and stimulus-independent

thought. Perceptual and Motor Processes, 23: 399-417.

Giambra, L.M. (1995) A laboratory method for investigating influences on switching

attention to task-unrelated imagery and thought. Conscious Cognit. 4, 1–21.

Teasdale, J.D., B.H. Dritschel, et al. (1995). Stimulus-independent thought depends on

central executive resources. Memory & Cognition, 23(5), 551-559.

Reichle, E.D., A.E. Reineberg et al. (2010). Eye movements during mindless reading.

Psychological Science, 21(9), 1300-1310.

Image References

Question? http://cuteoverload.com/2012/08/15/question/ Accessed 19/02/2013.

Cat Man Do. Testing Testing 1…2…3? (Part 1) http://catexpert.blogspot.com/2012/03/testing-testing-123-part-1.html Accessed 19/02/2013.

Frontoparietal Cortical networks for Directing Attentiion and The Eye to Visual Locations: Identical, Independent, or Overlapping Neural Systems? http://www.pnas.org/content/95/3/831/F3.expansion.html Accessed 20/02/2013.

http://keykristinedm310.blogspot.com/ Accessed 20/02/2013

RESOURCE THEORY VS. MINDLESS THEORY

Resource Theory and Mindless Theory represent two of the most prominent theories in the study of vigilance. A relatively more recent theory, namely Goal Habituation theory, has also attracted much attention in this field. This week’s post will examine these theories theories in detail, beginning with a summary of the main points of each theory and a comparative analysis of the key similarities and distinctions. As a departure from previous posts, this week’s post will not feature any in-depth summaries of the papers, but will instead reference them throughout this post for evidence and discussion. In the questions and comments section, we will then integrate this week’s readings with those of previous weeks by comparing the debates between mindless and resource theory with those discussed in previous weeks, specifically those concerning the key contributors to the vigilance decrement. After an examination of the competing theories, we will select the most compelling theory by referencing evidence from this week’s readings. Lastly, we will conclude with comments on links to neuroscience and possible future directions.

COMPETING THEORIES AND COMPARATIVE ANALYSIS

Resource Theory

The central tenet of resource theory is the contention that vigilance requires limited processing resources. As Helton and Russell (2011) and Ariga et. al.  (2011) elaborated in their papers, resource theory maintains that vigilance tasks require subjects to make continuous discriminations and thus deplete their mental and cognitive resources, resulting in a decline in their performance efficiency.  Notable supporters of resource theory include Parasurman and Warm, whose vigilance taxonomy and review of advances in vigilance research we discussed last week. Thus, advocates of resource theory espouse the view that the vigilance decrement is due to the decline in “available attention resources” and “cognitive resources available for information-processing” (Helton and Russell, 2011). The robustness of resource theory lies primarily in the abundance of supportive evidence coming from a variety of different experiments, from behavioral, to brain imaging, to mental workload studies, as Helton and Russell (2012) details in their paper. For instance, See et. al. showed objective increases in task difficulty was directly linked to greater lapses of sustained attention. Furthermore, declines in cerebral blood flow in areas of the brain associated with vigilance have also been shown to correspond with the vigilance decrement.  Ultimately, the resource theory posits that the vigilance decrement is a manifestation of the depletion of mental and cognitive resources throughout the course of a vigil.

Mindless Theory

In contrast to resource theory, mindless theory holds that the vigilance decrement arises from the subjects’ inattention or mindless. In short, the subjects demonstrate decreased attention to the vigilance task out of boredom. First described by Robertson and colleagues, the mindless theory states that subjects’ “supervisory attentional system loses effectiveness and ceases to focus awareness on the vigilance task” after a certain time of performing the same, repetitive task. As a result, subjects begin to respond to the task in a “thoughtless manner,” and acts out of routinization rather than attention (Ariga and Lleras, 2011). Since the Mindless Theory is relatively younger than Resource Theory, supportive evidence is slightly more limited. Much of the evidence for mindless theory comes from results of sustained attention to response task (SART) studies. Robertson et. al. (1996) describes this approach as well as its advantages over the conventional perceptual detection-based tests such as the Triplets test. Specifically, SART involves withholding of key presses in response to signals. The rationale behind this paradigm was the view that SART tasks require a “high level of continuous attention” and thus would test uniquely for sustained attention. Results confirmed this hypothesis and indicated that SART was sensitive to vigilance deficits and “predicts reported attentional failures in subjects.” Analysis of SART indices of attentional disengagement (measured through three variables, namely response time speed, anticipations, and omissions of signal responses) have shown a correlation between the vigilance decrement and the subject’s attentional disengagement, thus providing evidence for the mindless theory.

Goal Habituation Theory

The goal habituation theory, though similar to the Mindless Theory, has several important differences with the latter. Proposed by Ariga and Lleras (2011), this new theory attributes the vigilance decrement to the difficulty in maintaining an active goal for a “prolonged period of time.” Specifically, they argue that cognitive goals, such as maintaining attention through a vigilance task, also show habituation effects (described as the “eventual absence of representation of sustained stimulation”), and that it is this “goal habituation” that accounts for the decrement in vigilance tasks. In accordance with this theory, Ariga and Lleras argued “deactivating the vigilance goal would preempt full goal habituation by re-strengthening the goal’s activation,” and thus manifest in an enhancement in vigilance. Results indicated that the “mere prompt” of activating a different goal was sufficient to enhance vigilance, a finding that clearly supports the habituation hypothesis.

QUESTIONS AND COMMENTS

Blast From the Past: Parallels and Distinctions Between Current and Previous Debates

Examination of these competing theories brings to mind clear parallels of the debates we discussed in previous weeks on the key cause of the vigilance decrement. For instance, while signal detection theory held the background event rate responsible, Broadbent and Gregory attributed it to the decline in subject confidence. Upon a closer look, we find that the debate between resource, mindless, and goal habituation theories has clear echoes of the past debates. For instance, resource theory maintains the vigilance decrement is due to a depletion of mental resources, which is rather in line with Parasurman’s argument that memory load contributes to sensitivity decrements. To take this one step further, resource theory’s claim that cognitive and mental resources are depleted also echo See et. al.’s study on the necessity to examine the vigilance decrement in the context of the total task demands, in addition to memory load. Furthermore, the cognitive component addressed by resource theory is also in line with See et. al. and other researchers’ view that vigilance tasks require cognitive resources and that cognitive-based tasks may be different from perceptual-based tasks. Interestingly, however, while See et. al. saw a stabilization of performance and in some cases, a rise in performance, during cognitive tasks, resource theory does not take such observations into consideration. On another note, the Mindless Theory also falls in line with several of Scerbo (1998)’s findings. Specifically, the latter posited that boredom could have an effect in the vigilance decrement, which is clearly echoed in the Mindless Theory’s claims that the vigilance decrement arises out of inattention to the vigilance task. On a more “meta” level, I find the current debates and those that we discussed last week all share one similarity that may explain the existence of the debates: they all hypothesize that one factor or process is the key contributor to the vigilance decrement. However, as will be discussed in the section immediately following this one, the ideal theory should incorporate components of all the candidate theories.

Moment of Truth: Which Theory is Most Compelling (and Why)?

Okay, so here, I’m going to err…cheat a bit. I know we’re technically suppose to select one theory, but I don’t think there’s one theory that is clearly the winner. Moreover, I feel that quite possibly, the “correct theory,” is a mixture of all three theories. I believe the most compelling theory should have the evidence (and claims) of resource theory but also take into consideration the possibilities suggested by mindless and goal habituation theory. For something as complex as vigilance, I don’t think that any one variable or explanation could be the only correct explanation. To do so would be to neglect the complexity of the problem as well as that of the evidence. The key, at least in my opinion, is to recognize that the theories presented are not mutually exclusive. For me, the most compelling theory might look something like this: the depletion of mental and cognitive resources (which is proposed by resource theory) can be due to both mental fatigue and boredom, which may stem from goal habituation. While this is rudimentary, it takes into account many variables such as resource depletion and mental fatigue but also links together possible explanations into one compelling argument. Oh, and disclaimer: I’m not self-complimenting, really. Well, maybe just a tiny bit.

General Questions and Comments

            In this section, I would like to raise a general question that I have wondered about for a long time. It does not address this week’s papers specifically, per se, but this week’s assignment rekindled this question. I know the scientific method is the bible of science, and that everything begins with observation and a hypothesis. However, I feel that once we believe that something is true/i.e. have a hypothesis, we are almost certain to find evidence to support it. In short, it is possible to basically prove anything as long as we look for evidence in favor of our “hypothesis.” Yet, doesn’t this contribute to biased data and results? Aside from undermining the rigorous nature of science research, if this approach indeed biases our findings (and by virtue of being human, we all have preferences, etc.), and if that research is then used to produce clinically relevant products, isn’t this a significant problem? Clearly, I think the scientific method has significant merits. I’m just wondering about a possible flaw. I agree that most of this can be controlled by discipline, but sometimes, I feel that maybe starting out with no hypothesis but rather with the intention of studying something, may be more compelling. Just a thought though.

LINKS TO NEUROSCIENCE

I think it would be extremely interesting to examine the competing theories through the lens of neuroscience experiments. For resource theory, we would need to first define what constitutes “mental and cognitive resources.” We could begin by testing just a few variables such as memory and attention. We can then construct mouse models in which the mutant mice have impaired ability to process information or tire more quickly. If the resource theory is correct, then one would expect the mutant mice to demonstrate a quicker and more pronounced vigilance decrement than the wild type mice. A difficulty that has to be overcome is pinpoint the exact manipulation that would result in impaired information processing. One approach is legion of the hippocampus or frontal cortex. One could also use RNAi to silence genes that are known to be important in attention and information processing. For the mindless model, we can use human subjects. Specifically, we can use fMRI and transcranial brain imaging to see which areas of the brain are activated during repetitive and “boring” tasks, and most importantly, monitor the decline in activation intensity over the course of the vigil. To incorporate goal habituation theory, we can perform a similar procedure, but insert goal-changes sporadically. If the theory is correct, then one would expect to see in increase in activation of vigilance-related brain areas (every time a goal change is promoted) following a decline in those areas after a prolonged time.

REFERENCES

Robertson, I. H., T. Manly, et al. (1997). 'Oops!': performance correlates of everyday

attentional failures in traumatic brain injured and normal subjects. Neuropsychologia

35(6): 747-758.

Allan Cheyne, J., G. J. Solman, et al. (2009). Anatomy of an error: a bidirectional state

model of task engagement/disengagement and attention-related errors. Cognition

111(1): 98-113.

Helton, W. S. and P. N. Russell (2011). Feature absence-presence and two theories of

lapses of sustained attention. Psychol Res 75(5): 384-392.

Ariga, A. and Lleras, A. (2011). Brief and rare mental ‘‘breaks’’ keep you focused:

deactivation and reactivation of task goals preempt vigilance decrements. Cognition

118:439–443.

Helton, W. S., & Russell, P. N. (2012). Brief mental breaks and content-free cues may not

keep you focused. Experimental Brain Research, 219, 34–46.

Image References:

Graduate Studies in Neuroscience (Msc/PhD) http://www.uleth.ca/artsci/neuroscience/graduate-studies-neuroscience-mscphd. (Accessed 13/02/2013).

Eco-Cinema and Film Genre. The Land Before Time and Evolutionary Narratives. http://ecocinema.blogspot.com/2012/06/land-before-time-and-evolutionary.html. Accessed 13/02/2013)