Eye Movements as an Objective Measurement of Mind Wandering
We spent a lot of time mind wandering. Cognitive neuroscience has recently started investigating this phenomenon. However, the subjective nature of mind wandering makes capturing and measuring it exceptionally difficult. As a result, there is still no way to objectively measure mind wandering. In the majority of published studies researchers ask participants at random intervals how focused they are on a given task. Uzzaman and Joordens in a recently published paper explored the use of eye movements as an objective measure of mind wandering while participants performed a reading task.
Eye movements are thought to reflect (to some degree) cognitive processes (for a brief overview of eye movement research, see the Scholarpedia entry). Uzzaman et al. study was based on an earlier paper by Reichle, Reineberg, and Schooler (2010) who suggested that eye movements may provide an objective measure of mind wandering. Reichle et al. investigated this hypothesis by comparing the fixation-duration during mind wandering and normal reading episodes. The results were very encouraging and suggested that the participants’ eye movements became progressively decoupled from the ongoing task (i.e., text processing) during mind wandering episodes.
Uzzaman et al. used a reading task coupled with a self-classiﬁed probe-caught mind wandering paradigm to obtain a subjective account of mind wandering episodes. They recruited 30 participants who were explicitly informed of the deﬁnition of mind wandering episodes prior to the start of the experiment and were instructed that they would be asked to report their mind state at random intervals. The authors defined explicitly mind wandering “as reading without text comprehension, or thinking about anything other than the text on hand”. They also provided several examples to make sure the participants fully understood the concept.
The participants read sixteen pages of “War and Peace” by Tolstoy on a computer screen while their eye movements were tracked and recorded. Randomly every 2–3 min, a probe would appear on top of the text asking what was the mind state of the participants at this specific point. Participants would have to answer to continue the experiment. On average participants received 10 probes in total, in which mind wandering was reported on 49% of them.
The eye movement behaviours of the participants were categorised into mind wandering or reading conditions, based on their self-reports. This analysis was conducted for the 5 s time interval preceding the probe for reading and wandering conditions within each participant. Nine pairs of eye movement variables were analysed (e.g., count of blinks, fixations, saccades, fixation duration, within-word regression count), which displayed different degrees of sensitivity to mind wandering.
Statistical differences were found in two of the eye movement variables, run count and within-word regression count. Run count was defined as the “the total number of runs, where a run is two consecutive fixations within the same interest-area” and within-word regression count as “the sum of all fixation durations from when the word was first fixated upon, till the last fixation”.
Specifically, there were fewer within-word regressions for periods before mind wandering episodes compared to periods before reading reports (z = −2.305, p = 0.021). Also, the total run count was also lower during mind wandering episodes (z = −1.997, p = 0.046). In addition, fixation count, saccade count and total number of saccades within the interest-area were lower during mind wandering reports, although these variables fell slightly short of the conventional significance criterion (all z < −1.755,p > 0.079).
During comprehensive reading all the words were being cognitively processed deeply and effort was put forth. On the contrary, a different pattern was observed during mind wandering episodes, as it was suggested by the lower number and duration of within-word regressions that shows that the text was not being processed deeply, and as a result limited lexical information was being extracted. As a result, reading became less effortful and more automatic.
The current study revealed a correlation between subjective reports of mind wandering, and objective ocular behaviour. These findings could be further exploited in future studies and lead to the development of algorithms that would mathematically predict the likelihood of mind wandering based on eye movements. Such a development might provide valuable insights into the neural correlates of mind wandering.
Uzzaman, S., & Joordens, S. (2011). The eyes know what you are thinking: Eye movements as an objective measure of mind wandering Consciousness and Cognition, 20 (4), 1882-1886 DOI: 10.1016/j.concog.2011.09.010
Reichle ED, Reineberg AE, & Schooler JW (2010). Eye movements during mindless reading. Psychological science, 21 (9), 1300-10 PMID: 20679524