Exploring the varieties of experience during the mind-wandering state using pupilometry

Contemporary accounts suggests that experiences that can emerge in the mind-wandering state have a complex relationship to functional outcomes. Beneficial associations are linked to the ability to generate information that is discrepant from the external environment, which explains the observed links with creativity and planning (Baird, Smallwood et al. 2011, Baird, Smallwood et al. 2012, Ruby, Smallwood et al. 2013, Medea, Karapanagiotidis et al. 2016, Smeekens and Kane 2016). Less helpful associations link experiences during mind-wandering to worse performance (McVay and Kane 2009) and can be linked to unhappiness (Killingsworth and Gilbert 2010, Poerio, Totterdell et al. 2013). One hypothesis that has been proposed to account for this complex pattern of costs and benefits, is that mind-wandering is a heterogeneous state that contains different types of episodes, each with their unique relationship to other aspects of our lives.

The assumption that the mind-wandering state contains multiple states provides a simple intuitive explanation for the complex link with other aspects of cognition and emotion because different types of experience would be linked to different patterns of outcomes. It also places at a premium the ability to determine what the different features of experiences are that have different features. One way that our research has attempted to deal with this issue, is to attempt to link experiences during mind-wandering to objective markers such as measures of ongoing physiology (Engert, Smallwood et al. 2014), neural function (Smallwood, Karapanagiotidis et al. 2016) or measures of planning (Medea, Karapanagiotidis et al. 2016). These observations help ground our measurements of experience, since they link them to meaningful external measurements.

In a recent study led by Mahiko Konishi, and published in the journal Cognition (Konishi, Brown et al. 2017), we tested whether momentary examples of different types of experiential content, yield patterns that can be detected in an indirect measure of cognition: pupil dilation. We used an eye tracker to measure the size of a participants’ pupil while they performed a simple laboratory test. We employed a task that allowed us to manipulate the amount of mind-wandering that participants engage in through the variation in the role of working memory in the task. We used experience sampling to describe the patterns of experience that emerge during the mind-wandering state. To establish a stable relationship between ongoing physiology and experience, we asked 30 participants to come into the laboratory on several different laboratory sessions.

Our results suggested that the pupil signal is able to separate different types of experience. We found that task unrelated thought was related to pupils with a smaller diameter, a pattern that was most obvious in the simple non-demanding condition of our experiment. However, examination of the relationship between pupil dilation and different types of experience revealed that this patterns was specific to particular types of mental content. We found that smaller pupils were a hallmark of experiences that are linked to the past, and that are intrusive in nature. In contrast, the occurrence of thoughts focused on the future, a common feature of the mind-wandering state (Baird, Smallwood et al. 2011), was not linked to pupil size. Instead people tended to think about the future more often when the task was easy, a pattern frequently observed in these sorts of studies (Smallwood, Nind et al. 2009).

Smaller pupils linked to past focus, might explain why functional decoupling between the medial prefrontal cortex and visual cortex is associated with this aspect of experience (Smallwood, Karapanagiotidis et al. 2016). Possibly, constraining the amount of light that enters the retina, could reduce the coupling between visual cortex and regions of the medial prefrontal cortex. Moreover, the common association between small pupils and experiences with either a focus on the past, or with an intrusive nature, may suggest that smaller pupils are a signature of links between affective disturbance, since past related thoughts can be linked to unhappiness and depression (Smallwood and O’Connor 2011).  Most importantly, this study provides important evidence that the mind-wandering state is heterogeneous, since were were able to identify objective features related to specific aspect of ongoing experience by monitoring the pupil signal.


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Baird, B., J. Smallwood and J. W. Schooler (2011). “Back to the future: autobiographical planning and the functionality of mind-wandering.” Conscious Cogn 20(4): 1604-1611.

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Killingsworth, M. A. and D. T. Gilbert (2010). “A wandering mind is an unhappy mind.” Science 330(6006): 932.

Konishi, M., K. Brown, L. Battaglini and J. Smallwood (2017). “When attention wanders: Pupillometric signatures of fluctuations in external attention.” Cognition 168: 16-26.

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Smallwood, J., T. Karapanagiotidis, F. Ruby, B. Medea, I. de Caso, M. Konishi, H. T. Wang, G. Hallam, D. S. Margulies and E. Jefferies (2016). “Representing Representation: Integration between the Temporal Lobe and the Posterior Cingulate Influences the Content and Form of Spontaneous Thought.” PLoS One 11(4): e0152272.

Smallwood, J., L. Nind and R. C. O’Connor (2009). “When is your head at? An exploration of the factors associated with the temporal focus of the wandering mind.” Conscious Cogn 18(1): 118-125.

Smallwood, J. and R. C. O’Connor (2011). “Imprisoned by the past: unhappy moods lead to a retrospective bias to mind wandering.” Cogn Emot 25(8): 1481-1490.

Smeekens, B. A. and M. J. Kane (2016). “Working Memory Capacity, Mind Wandering, and Creative Cognition: An Individual-Differences Investigation into the Benefits of Controlled Versus Spontaneous Thought.” Psychol Aesthet Creat Arts 10(4): 389-415.


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